AQA Triple Science: Chemistry — Recall & Retrieval

4.1.1.1 Atoms, Elements and Compounds

1.

What is an atom?

An atom is the smallest part of an element that can exist and still have the properties of that element.

2.

What is an element?

An element is a substance made of only one type of atom.

3.

What is a compound?

A compound is a substance made from two or more different elements chemically bonded together.

4.

What is the difference between an element and a compound?

An element contains only one type of atom, whereas a compound contains different elements chemically bonded together.

5.

How can compounds be separated into their elements?

Compounds can be separated into their elements by chemical reactions, such as electrolysis.

6.

Explain why a chemical reaction is needed to separate a compound but not a mixture.

A chemical reaction is needed to separate a compound because chemical bonds must be broken, whereas mixtures are only physically combined and can be separated by physical methods.

4.1.1.2 Mixtures

1.

What is a mixture?

A mixture is two or more substances mixed together without chemical bonding.

2.

Do substances in a mixture keep their own chemical properties?

Yes, substances in a mixture keep their own chemical properties.

3.

Name four methods used to separate mixtures.

Filtration, crystallisation, distillation and chromatography.

4.

Which separation technique is used to separate dyes in ink?

Chromatography is used to separate dyes in ink.

5.

Which separation technique is used to separate a soluble solid from a solution?

Crystallisation is used to separate a soluble solid from a solution.

6.

Explain why separating a mixture does not involve a chemical reaction.

Separating a mixture does not involve a chemical reaction because no chemical bonds are broken or formed.

4.1.1.3 The Development of the Model of the Atom

1.

What model of the atom was accepted before the electron was discovered?

The accepted model before the electron was discovered was the solid sphere model (Dalton’s model).

2.

What did the plum pudding model suggest about the atom?

The plum pudding model suggested that atoms were a ball of positive charge with negatively charged electrons embedded in it.

3.

Which experiment led to the nuclear model of the atom?

Rutherford’s alpha scattering experiment led to the nuclear model of the atom.

4.

What did Niels Bohr suggest about electrons?

Niels Bohr suggested that electrons exist in fixed energy levels or shells around the nucleus.

5.

Which scientist discovered the neutron?

James Chadwick discovered the neutron.

6.

Explain why Rutherford's alpha scattering experiment caused the atomic model to change.

Rutherford’s experiment showed that most of the atom was empty space, with a small dense positive nucleus, causing the atomic model to change.

4.1.1.4 Relative Electrical Charges of Subatomic Particles

1.

What is the relative charge of a proton?

A proton has a relative charge of +1.

2.

What is the relative charge of a neutron?

A neutron has a relative charge of 0.

3.

What is the relative charge of an electron?

An electron has a relative charge of -1.

4.

What is the atomic number of an element?

The atomic number is the number of protons in an atom.

5.

Why does an atom have no overall charge?

An atom has no overall charge because it has equal numbers of protons and electrons.

6.

Explain why atoms of different elements have different chemical properties.

Atoms of different elements have different chemical properties because they have different numbers of protons and different electron arrangements.

4.1.1.5 Size and Mass of Atoms

1.

What is the approximate radius of an atom?

The approximate radius of an atom is about 0.1 nanometres (1 × 10⁻¹⁰ m).

2.

Where is almost all of an atom's mass found?

Almost all of an atom’s mass is found in the nucleus.

3.

What is the mass number of an atom?

The mass number is the total number of protons and neutrons in an atom.

4.

What is an isotope?

An isotope is an atom of the same element with the same number of protons but a different number of neutrons.

5.

Calculate the number of neutrons in an atom with mass number 35 and atomic number 17.

Number of neutrons = mass number − atomic number = 35 − 17 = 18 neutrons.

6.

Explain why isotopes of the same element have similar chemical properties.

Isotopes have similar chemical properties because they have the same number of electrons and the same electron arrangement.

4.1.1.6 Relative Atomic Mass

1.

What is relative atomic mass?

Relative atomic mass is the weighted average mass of atoms of an element compared with one-twelfth of the mass of carbon-12.

2.

Why is relative atomic mass often not a whole number?

Relative atomic mass is often not a whole number because it is an average of different isotopes.

3.

What does relative atomic mass take into account?

Relative atomic mass takes into account the masses and abundances of isotopes.

4.

Which particles differ in isotopes of the same element?

The particles that differ in isotopes are neutrons.

5.

How do you calculate the relative atomic mass from isotope abundance data?

Relative atomic mass is calculated by multiplying each isotope’s mass by its abundance, adding the results, then dividing by the total abundance.

6.

Explain why chlorine has a relative atomic mass of 35.5 rather than exactly 35 or 37.

Chlorine has a relative atomic mass of 35.5 because it is a mixture of chlorine-35 and chlorine-37 isotopes in different abundances.

4.1.1.7 Electronic Structure

1.

Where are electrons found in an atom?

Electrons are found in shells around the nucleus.

2.

Which shell fills first?

The first shell fills first.

3.

State the electronic structure of sodium.

Sodium has the electronic structure 2,8,1.

4.

State the electronic structure of oxygen.

Oxygen has the electronic structure 2,6.

5.

Write the electronic structure of calcium.

Calcium has the electronic structure 2,8,8,2.

6.

Explain how electronic structure determines an element's position in the periodic table.

The number of occupied electron shells determines the period, and the number of electrons in the outer shell determines the group.

4.1.2.1 The Periodic Table

1.

In what order are elements arranged in the periodic table?

Elements are arranged in order of increasing atomic number.

2.

What is a group?

A group is a vertical column of elements in the periodic table.

3.

What is a period?

A period is a horizontal row of elements in the periodic table.

4.

Why do elements in the same group have similar chemical properties?

Elements in the same group have similar chemical properties because they have the same number of electrons in their outer shell.

5.

How can you predict the reactivity of an element using the periodic table?

Reactivity can be predicted by observing trends down a group.

6.

Explain how an element's position is related to its electron arrangement.

An element’s position is related to its electron arrangement because the number of shells determines the period and outer electrons determine the group.

4.1.2.2 Development of the Periodic Table

1.

Who developed the first successful periodic table?

Dmitri Mendeleev developed the first successful periodic table.

2.

How did Mendeleev arrange the elements?

Mendeleev arranged elements by increasing atomic weight and grouped elements with similar properties.

3.

Why did Mendeleev leave gaps in his table?

Mendeleev left gaps because he predicted that undiscovered elements would fit there.

4.

What happened to the gaps in Mendeleev's table?

The gaps were later filled when new elements were discovered with properties close to Mendeleev’s predictions.

5.

Why was arranging elements by atomic weight sometimes incorrect?

Arranging elements by atomic weight was sometimes incorrect because isotopes have different masses.

6.

Explain why Mendeleev's periodic table was eventually accepted.

Mendeleev’s table was accepted because his predictions for undiscovered elements were accurate.

4.1.2.3 Metals and Non-metals

1.

Where are metals found in the periodic table?

Metals are found on the left and centre of the periodic table.

2.

Where are non-metals found in the periodic table?

Non-metals are found on the right side of the periodic table.

3.

What type of ions do metals form?

Metals form positive ions.

4.

What type of ions do non-metals form?

Non-metals form negative ions.

5.

State two physical properties of metals.

Metals are good conductors of electricity and are malleable.

6.

Explain why metals and non-metals have different chemical properties.

Metals and non-metals have different chemical properties because they have different electron arrangements and form different ions.

4.1.2.4 Group 0

1.

What are the Group 0 elements called?

Group 0 elements are called noble gases.

2.

Why are noble gases unreactive?

Noble gases are unreactive because they have a full outer electron shell.

3.

Which Group 0 element has only two electrons in its outer shell?

Helium has only two electrons in its outer shell.

4.

How does boiling point change down Group 0?

Boiling points increase down Group 0.

5.

Which noble gas has the lowest boiling point?

Helium has the lowest boiling point.

6.

Explain why the boiling points increase down Group 0.

Boiling points increase down Group 0 because atoms become larger and have stronger intermolecular forces.

4.1.2.5 Group 1

1.

What are the Group 1 elements called?

Group 1 elements are called alkali metals.

2.

How many electrons do Group 1 elements have in their outer shell?

Group 1 elements have one electron in their outer shell.

3.

How does reactivity change down Group 1?

Reactivity increases down Group 1.

4.

What gas is produced when Group 1 metals react with water?

Hydrogen gas is produced when Group 1 metals react with water.

5.

Name the products formed when sodium reacts with chlorine.

Sodium reacts with chlorine to form sodium chloride (NaCl).

6.

Explain why Group 1 metals become more reactive down the group.

Group 1 metals become more reactive down the group because the outer electron is further from the nucleus and easier to lose.

4.1.2.6 Group 7

1.

What are the Group 7 elements called?

Group 7 elements are called halogens.

2.

How many electrons do Group 7 elements have in their outer shell?

Group 7 elements have seven electrons in their outer shell.

3.

How does reactivity change down Group 7?

Reactivity decreases down Group 7.

4.

What is a displacement reaction?

A displacement reaction occurs when a more reactive element replaces a less reactive element in a compound.

5.

Which halogen can displace iodine from potassium iodide solution?

Chlorine can displace iodine from potassium iodide solution.

6.

Explain why chlorine is more reactive than bromine.

Chlorine is more reactive than bromine because chlorine atoms gain an electron more easily due to their smaller size.

4.1.3.1 Comparison with Group 1 Elements (Triple Only)

1.

What are the transition elements?

Transition elements are metals found in the central block of the periodic table.

2.

Are transition metals more or less reactive than Group 1 metals?

Transition metals are less reactive than Group 1 metals.

3.

Name one physical property in which transition metals differ from Group 1 metals.

Transition metals have higher melting points than Group 1 metals.

4.

Name one transition metal used in everyday life.

Iron is a transition metal used in everyday life.

5.

State two differences between transition metals and Group 1 metals.

Transition metals are less reactive and harder than Group 1 metals.

6.

Explain why transition metals are suitable for making structures and tools.

Transition metals are suitable for structures and tools because they are strong, hard and have high melting points.

4.1.3.2 Typical Properties (Triple Only)

1.

What is a catalyst?

A catalyst is a substance that increases the rate of reaction without being used up.

2.

Name one typical property of transition metals.

A typical property of transition metals is that they form coloured compounds.

3.

What colour are many transition metal compounds?

Many transition metal compounds are coloured.

4.

Can transition metals form ions with different charges?

Yes, transition metals can form ions with different charges.

5.

Give one example of a transition metal used as a catalyst.

Iron is used as a catalyst in the Haber process.

6.

Explain why transition metals are widely used in industry.

Transition metals are widely used in industry because they are strong, have useful properties and can act as catalysts.

Topic 1 Review

1.

What is the difference between an element and a compound?

An element contains one type of atom, while a compound contains two or more elements chemically bonded together.

2.

What particle determines the identity of an element?

The particle that determines the identity of an element is the proton.

3.

State the relative charges of the three subatomic particles.

Proton = +1, neutron = 0, electron = -1.

4.

Explain why isotopes have different mass numbers.

Isotopes have different mass numbers because they contain different numbers of neutrons.

5.

Compare the properties of Group 1 and Group 7 elements.

Group 1 elements are reactive metals that become more reactive down the group; Group 7 elements are reactive non-metals that become less reactive down the group.

6.

Explain how the arrangement of electrons determines an element's position and reactivity in the periodic table.

Electron arrangement determines an element’s position because outer electrons determine its group and number of shells determine its period. It also determines reactivity because reactions involve gaining, losing or sharing electrons.

4.2.1.1 Chemical Bonds

1.

What are the three types of strong chemical bond?

The three types of strong chemical bonding are ionic bonding, covalent bonding and metallic bonding.

2.

Which type of bonding occurs between a metal and a non-metal?

Ionic bonding occurs between a metal and a non-metal.

3.

Which type of bonding occurs between non-metals?

Covalent bonding occurs between non-metals.

4.

What type of bonding is found in metals?

Metallic bonding is found in metals.

5.

What holds atoms or ions together in chemical bonds?

Chemical bonds are held together by strong electrostatic forces of attraction between particles.

6.

Explain the difference between ionic, covalent and metallic bonding.

Ionic bonding involves attraction between oppositely charged ions, covalent bonding involves sharing electrons, and metallic bonding involves attraction between positive metal ions and delocalised electrons.

4.2.1.2 Ionic Bonding

1.

What happens to electrons during ionic bonding?

Electrons are transferred from one atom to another during ionic bonding.

2.

What type of ion is formed when a metal loses electrons?

A metal loses electrons to form a positive ion.

3.

What type of ion is formed when a non-metal gains electrons?

A non-metal gains electrons to form a negative ion.

4.

Show aluminium oxide bonding using a dot and cross diagram

Aluminium oxide forms when two aluminium atoms lose six total electrons (three each) and three oxygen atoms gain these electrons (2 each), forming Al³⁺ and O²⁻ ions in a giant ionic lattice.

5.

Why do atoms form ions during ionic bonding?

Atoms form ions during ionic bonding to achieve a full outer electron shell and become more stable.

6.

Explain how sodium and chlorine form sodium chloride.

Sodium loses one electron to form Na⁺ and chlorine gains one electron to form Cl⁻. The oppositely charged ions attract to form sodium chloride.

4.2.1.3 Ionic Compounds

1.

What structure do ionic compounds have?

Ionic compounds have a giant ionic lattice structure.

2.

What force holds ions together in an ionic lattice?

Ions are held together by strong electrostatic forces of attraction.

3.

Why do ionic compounds have high melting points?

Ionic compounds have high melting points because strong forces between ions require lots of energy to overcome.

4.

What is an empirical formula?

An empirical formula shows the simplest whole-number ratio of atoms or ions in a compound.

5.

Why can molten ionic compounds conduct electricity?

Molten ionic compounds conduct electricity because ions are free to move and carry charge.

6.

Explain why solid ionic compounds do not conduct electricity.

Solid ionic compounds do not conduct electricity because the ions are fixed in place and cannot move.

4.2.1.4 Covalent Bonding

1.

What happens to electrons in covalent bonding?

Electrons are shared between atoms during covalent bonding.

2.

Between which types of elements does covalent bonding occur?

Covalent bonding occurs between non-metal elements.

3.

Show the bonding in carbon dioxide using a dot and cross diagram.

Carbon dioxide has two carbon-oxygen double covalent bonds, with carbon sharing two pairs of electrons with each oxygen atom.

4.

Name one giant covalent substance.

Diamond is an example of a giant covalent substance.

5.

Name one substance made of small covalent molecules.

Water is an example of a substance made of small covalent molecules.

6.

Explain why covalent bonds are described as strong bonds.

Covalent bonds are strong because they involve strong electrostatic attractions between the shared electrons and nuclei.

4.2.1.5 Metallic Bonding

1.

What are metals made of?

Metals are made of positive ions arranged in a regular lattice surrounded by delocalised electrons.

2.

What are delocalised electrons?

Delocalised electrons are electrons that are free to move through the metal.

3.

Show metallic bonding in calcium metal.

Calcium metal consists of Ca²⁺ ions surrounded by delocalised electrons.

4.

Why can electrons move through a metal?

Electrons can move through a metal because they are delocalised.

5.

What is meant by metallic bonding?

Metallic bonding is the strong attraction between positive metal ions and delocalised electrons.

6.

Explain why metals are good electrical conductors.

Metals conduct electricity because delocalised electrons carry electrical charge through the structure.

4.2.2.1 The Three States of Matter

1.

What are the three states of matter?

The three states of matter are solid, liquid and gas.

2.

What happens during melting?

Melting occurs when a solid changes into a liquid because particles gain enough energy to move past each other.

3.

What happens during condensation?

Condensation occurs when a gas changes into a liquid because particles lose energy.

4.

What happens to particles when a substance is heated?

When a substance is heated, particles gain kinetic energy and move faster.

5.

Why do different substances have different melting points?

Different substances have different melting points because the forces between particles are different strengths.

6.

Explain why more energy is needed to melt some substances than others.

More energy is needed to melt some substances because stronger forces between particles require more energy to overcome.

4.2.2.2 State Symbols

1.

What state symbol represents a solid?

A solid is represented by (s).

2.

What state symbol represents a liquid?

A liquid is represented by (l).

3.

What state symbol represents a gas?

A gas is represented by (g).

4.

What does (aq) mean?

(aq) means dissolved in water (aqueous solution).

5.

Why are state symbols included in chemical equations?

State symbols show the physical states of reactants and products in chemical equations.

6.

Write the equation of hydrochloric acid reacting with solid magnesium including correct state symbols for both reactants and products.

Mg(s) + 2HCl(aq) → MgCl₂(aq) + H₂(g)

4.2.2.3 Properties of Ionic Compounds

1.

Why do ionic compounds have high melting points?

Ionic compounds have high melting points because strong ionic bonds require lots of energy to break.

2.

Why do ionic compounds have high boiling points?

Ionic compounds have high boiling points because strong forces between ions require large amounts of energy to overcome.

3.

When do ionic compounds conduct electricity?

Ionic compounds conduct electricity when molten or dissolved in water.

4.

Why do molten ionic compounds conduct electricity?

Molten ionic compounds conduct electricity because ions are free to move.

5.

Why do solid ionic compounds not conduct electricity?

Solid ionic compounds do not conduct electricity because ions cannot move.

6.

Explain how the structure of ionic compounds affects their properties.

The giant ionic lattice structure gives ionic compounds high melting points and allows conduction only when ions are mobile.

4.2.2.4 Properties of Small Molecules

1.

What type of forces exist between small molecules?

Small molecules have weak intermolecular forces between molecules.

2.

Are intermolecular forces stronger or weaker than covalent bonds?

Intermolecular forces are weaker than covalent bonds.

3.

Why do small molecular substances have low melting points?

Small molecular substances have low melting points because little energy is needed to overcome intermolecular forces.

4.

Do small molecular substances conduct electricity?

Small molecular substances do not conduct electricity because they have no charged particles that can move.

5.

How does molecule size affect boiling point?

Larger molecules have stronger intermolecular forces and higher boiling points.

6.

Explain why covalent bonds are not broken when a molecular substance melts.

Covalent bonds are not broken when a molecular substance melts; only intermolecular forces are overcome.

4.2.2.5 Polymers

1.

What is a polymer?

A polymer is a long chain molecule made from many repeating units.

2.

What type of bonding joins atoms within a polymer?

Atoms within a polymer are joined by strong covalent bonds.

3.

Why are polymers solids at room temperature?

Polymers are solids at room temperature because their long chains have strong forces between them.

4.

What type of molecules do polymers contain?

Polymers contain very large molecules made from repeating units.

5.

Give one example of a polymer.

Poly(ethene) is an example of a polymer.

6.

Explain why polymers generally have higher melting points than small molecular substances.

Polymers generally have higher melting points than small molecular substances because they have stronger forces between their long chains.

4.2.2.6 Giant Covalent Structures

1.

What is a giant covalent structure?

A giant covalent structure is a structure where atoms are joined by many strong covalent bonds in a large network.

2.

Name three giant covalent substances.

Diamond, graphite and graphene are giant covalent substances.

3.

Why do giant covalent substances have very high melting points?

Giant covalent substances have very high melting points because many strong covalent bonds must be broken.

4.

What type of bond must be broken to melt a giant covalent structure?

Covalent bonds must be broken to melt a giant covalent structure.

5.

Which giant covalent substance conducts electricity?

Graphite conducts electricity.

6.

Explain why diamond and graphite have different properties.

Diamond and graphite have different properties because their atoms are arranged differently.

4.2.2.7 Properties of Metals and Alloys

1.

Why do metals have high melting points?

Metals have high melting points because strong metallic bonds require lots of energy to break.

2.

Why can pure metals be bent easily?

Pure metals can be bent easily because layers of atoms can slide over each other.

3.

What is an alloy?

An alloy is a mixture of a metal with one or more other elements.

4.

Why are alloys harder than pure metals?

Alloys are harder than pure metals because different-sized atoms disrupt the regular layers and prevent them sliding.

5.

Give one example of an alloy.

Brass is an example of an alloy.

6.

Explain why alloys are often used instead of pure metals.

Alloys are often used instead of pure metals because they are stronger and more useful.

4.2.2.8 Metals as Conductors

1.

Why do metals conduct electricity?

Metals conduct electricity because they contain delocalised electrons.

2.

What particles carry electrical charge through a metal?

Delocalised electrons carry electrical charge through a metal.

3.

Why do metals conduct thermal energy well?

Metals conduct thermal energy well because delocalised electrons transfer energy quickly.

4.

What are delocalised electrons free to do?

Delocalised electrons are free to move through the metal structure.

5.

Name one property that makes metals useful for electrical wiring.

Metals are useful for electrical wiring because they are good electrical conductors and are ductile.

6.

Explain how metallic bonding allows metals to conduct heat and electricity.

Metallic bonding allows conduction because electrons are free to move and transfer charge and energy.

4.2.3.1 Diamond

1.

How many covalent bonds does each carbon atom form in diamond?

Each carbon atom forms four covalent bonds in diamond.

2.

What type of structure does diamond have?

Diamond has a giant covalent structure.

3.

Why is diamond very hard?

Diamond is very hard because each carbon atom is strongly bonded to four others.

4.

Why does diamond have a very high melting point?

Diamond has a very high melting point because many strong covalent bonds must be broken.

5.

Does diamond conduct electricity?

Diamond does not conduct electricity.

6.

Explain why diamond does not conduct electricity.

Diamond does not conduct electricity because all electrons are held in covalent bonds and none are delocalised.

4.2.3.2 Graphite

1.

How many covalent bonds does each carbon atom form in graphite?

Each carbon atom forms three covalent bonds in graphite.

2.

What shape are the layers in graphite?

Graphite consists of layers of carbon atoms arranged in hexagonal shapes.

3.

Why can graphite conduct electricity?

Graphite conducts electricity because it has delocalised electrons.

4.

Why can the layers in graphite slide over each other?

Layers in graphite slide over each other because weak forces exist between the layers.

5.

State one use of graphite.

Graphite is used as a lubricant.

6.

Explain why graphite is soft but diamond is hard.

Graphite is soft because layers slide easily, whereas diamond is hard because of its strong three-dimensional bonding.

4.2.3.3 Graphene and Fullerenes

1.

What is graphene?

Graphene is a single layer of carbon atoms arranged in a hexagonal structure.

2.

What is a fullerene?

A fullerene is a molecule made from carbon atoms arranged in a hollow shape.

3.

What shape is Buckminsterfullerene (C₆₀)?

Buckminsterfullerene (C₆₀) has a spherical shape.

4.

What are carbon nanotubes?

Carbon nanotubes are cylindrical structures made from carbon atoms.

5.

Give one use of graphene or carbon nanotubes.

Graphene can be used in electronics or sensors.

6.

Explain why graphene is useful in electronics.

Graphene is useful in electronics because it conducts electricity and is very thin and strong.

4.2.4.1 Sizes of Particles and Their Properties (Triple Only)

1.

What size range do nanoparticles have?

Nanoparticles have sizes between 1 and 100 nanometres.

2.

What happens to surface area to volume ratio as particles get smaller?

Surface area to volume ratio increases as particles get smaller.

3.

Why do nanoparticles have different properties from bulk materials?

Nanoparticles have different properties because they have a much larger surface area compared with their volume.

4.

What does the prefix nano- mean?

Nano- means one billionth (10⁻⁹).

5.

Why are smaller quantities of nanoparticles often needed?

Smaller quantities of nanoparticles are often needed because they have a large surface area to volume ratio.

6.

Explain why nanoparticles are more reactive than larger particles.

Nanoparticles are more reactive because more particles are exposed at the surface.

4.2.4.2 Uses of Nanoparticles (Triple Only)

1.

Give one use of nanoparticles in medicine.

Nanoparticles can be used in medicine for targeted drug delivery.

2.

Give one use of nanoparticles in cosmetics.

Nanoparticles can be used in cosmetics such as sunscreen.

3.

Give one industrial use of nanoparticles.

Nanoparticles can be used industrially as catalysts.

4.

State one advantage of using nanoparticles.

An advantage is that small amounts can be effective because of their large surface area.

5.

State one possible risk of using nanoparticles.

A possible risk is that nanoparticles may enter cells and cause unknown health effects.

6.

Explain why scientists continue to research nanoparticle applications.

Scientists continue researching nanoparticles because they have many potential applications but their risks must be understood.

Topic 2 Review

1.

Name the three types of strong chemical bonding.

The three types of strong chemical bonding are ionic, covalent and metallic.

2.

What is the difference between ionic and covalent bonding?

Ionic bonding involves electron transfer and attraction between ions; covalent bonding involves sharing electrons between atoms.

3.

Explain why ionic compounds only conduct electricity when molten or dissolved.

Ionic compounds only conduct electricity when molten or dissolved because ions must be free to move.

4.

Compare the structures of diamond and graphite.

Diamond has a three-dimensional giant covalent structure and is hard; graphite has layers with delocalised electrons and is soft.

5.

Explain why alloys are harder than pure metals.

Alloys are harder than pure metals because different atoms disrupt the layers and stop them sliding.

6.

Describe how bonding and structure determine the physical properties of substances.

Bonding and structure determine physical properties because the type and strength of forces between particles affect melting point, conductivity, hardness and flexibility.

4.3.1.1 Conservation of Mass and Balanced Chemical Equations

1.

What does the law of conservation of mass state?

The law of conservation of mass states that mass is not created or destroyed during a chemical reaction.

2.

Why must chemical equations be balanced?

Chemical equations must be balanced because the same number of each type of atom must be present on both sides of the equation.

3.

What does a coefficient in a chemical equation show?

A coefficient shows the number of molecules or moles of a substance.

4.

What is the difference between a coefficient and a subscript?

A coefficient is a number placed in front of a formula and changes the amount of a substance; a subscript is part of the formula and shows the number of atoms in one molecule.

5.

Balance the equation: H₂ + O₂ → H₂O.

2H₂ + O₂ → 2H₂O.

6.

Explain why mass stays the same during a chemical reaction.

Mass stays the same because atoms are rearranged but not created or destroyed.

4.3.1.2 Relative Formula Mass

1.

What does relative formula mass (Mr) mean?

Relative formula mass (Mr) is the sum of the relative atomic masses of all atoms in a formula.

2.

How is relative formula mass calculated?

Relative formula mass is calculated by adding together the relative atomic masses of all atoms in the formula.

3.

What information is needed to calculate Mr?

The relative atomic masses of all elements in the compound are needed.

4.

Calculate the Mr of H₂O.

Mr of H₂O = (2 × 1) + 16 = 18.

5.

Calculate the percentage by mass of oxygen in water.

Percentage by mass of oxygen in water = (16 ÷ 18) × 100 = 88.9%.

6.

Explain why relative formula mass is useful in chemistry.

Relative formula mass is useful because it allows chemists to calculate reacting amounts and masses.

4.3.1.3 Mass Changes When a Reactant or Product is a Gas

1.

Why can the mass increase when magnesium burns?

The mass can increase when magnesium burns because magnesium reacts with oxygen from the air.

2.

Why can the mass decrease when a metal carbonate is heated?

The mass can decrease when a metal carbonate is heated because carbon dioxide gas escapes.

3.

What gas is produced during the thermal decomposition of a metal carbonate?

Carbon dioxide is produced during the thermal decomposition of a metal carbonate.

4.

What happens to the mass in a closed system?

In a closed system, the total mass remains constant.

5.

Why do some reactions appear to lose mass?

Some reactions appear to lose mass because gases escape into the surroundings.

6.

Explain why mass is conserved even when gases are produced.

Mass is conserved because gases still contain the same atoms; they have just left the reaction container.

4.3.1.4 Chemical Measurements

1.

What is meant by uncertainty in a measurement?

Uncertainty is the amount by which a measurement may vary from the true value.

2.

What is meant by the mean of a set of results?

The mean is the average of a set of results.

3.

What is the range of a set of results?

The range is the difference between the highest and lowest results.

4.

Why are repeat measurements carried out?

Repeat measurements are carried out to improve reliability and identify anomalies.

5.

How can the uncertainty of repeated measurements be estimated?

The uncertainty of repeated measurements can be estimated using half the range.

6.

Explain why measurements in science always have some uncertainty.

Measurements always have some uncertainty because instruments have limits of accuracy and human measurements vary.

4.3.2.1 Moles (Higher Tier)

1.

What is the unit used to measure the amount of substance?

The unit used to measure the amount of substance is the mole (mol).

2.

What is one mole?

One mole is the amount of substance containing 6.02 × 10²³ particles.

3.

What is the Avogadro constant?

The Avogadro constant is 6.02 × 10²³ particles per mole.

4.

Write the equation linking moles, mass and relative formula mass.

Moles = mass ÷ relative formula mass.

5.

Calculate the number of moles in 36 g of water.

Moles in 36 g of water = 36 ÷ 18 = 2 mol.

6.

Calculate the mass of 0.25 moles of sodium chloride (NaCl).

Mass of 0.25 mol NaCl = 0.25 × 58.5 = 14.6 g.

4.3.2.2 Amounts of Substances in Equations (Higher Tier)

1.

What does a balanced equation show about moles?

A balanced equation shows the ratio of moles of reactants and products.

2.

Why must equations be balanced before calculations are carried out?

Equations must be balanced before calculations because mole ratios depend on the coefficients.

3.

How many moles of hydrogen are produced when one mole of magnesium reacts with hydrochloric acid?

One mole of magnesium reacts with hydrochloric acid to produce one mole of hydrogen.

4.

What is the first step in a mole calculation?

The first step is to calculate the number of moles of the known substance.

5.

Calculate the mass of magnesium oxide produced from 24 g of magnesium.

24 g magnesium = 1 mol Mg, so it produces 1 mol MgO = 40 g magnesium oxide.

6.

Calculate the mass of aluminium oxide produced when 135g of aluminium is burned in air.

135 g aluminium = 5 mol Al, producing 2.5 mol Al₂O₃ = 255 g aluminium oxide.

4.3.2.3 Using Moles to Balance Equations (Higher Tier)

1.

Why are moles used to balance chemical equations?

Moles are used because equations show ratios of particles and reacting amounts.

2.

What must masses be converted into before balancing by calculation?

Masses must be converted into moles before balancing by calculation.

3.

What type of ratio is used to balance equations?

A mole ratio is used to balance equations.

4.

Balance the chemical equation for photosynthesis using the following masses: 264 g carbon dioxide reacts with 108 g water to produce 180 g glucose and 192 g oxygen.

6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂.

5.

Balance the chemical equation for the complete combustion of methane using the following masses: 16 g methane reacts with 64 g oxygen to produce 44 g carbon dioxide and 36 g water.

CH₄ + 2O₂ → CO₂ + 2H₂O.

6.

Balance a chemical equation between magnesium and oxygen using the following masses: 24 g magnesium reacts with 16 g oxygen to produce 40 g magnesium oxide.

2Mg + O₂ → 2MgO.

4.3.2.4 Limiting Reactants (Higher Tier)

1.

What is a limiting reactant?

A limiting reactant is the reactant that is completely used up first in a reaction.

2.

Why is one reactant often used in excess?

One reactant is often used in excess to ensure another reactant reacts completely.

3.

What happens when the limiting reactant is completely used up?

When the limiting reactant is used up, the reaction stops.

4.

Which reactant determines the amount of product formed?

The limiting reactant determines the amount of product formed.

5.

Identify the limiting reactant from given amounts.

The limiting reactant is identified by comparing mole ratios of reactants.

6.

Explain how the limiting reactant affects the yield of a reaction.

The limiting reactant controls the yield because no more product can form once it is exhausted.

4.3.2.5 Concentration of Solutions

1.

What is concentration?

Concentration is the amount of solute dissolved in a given volume of solution.

2.

What units are used for concentration in g/dm³?

Concentration in g/dm³ is measured in grams per cubic decimetre.

3.

Write the equation linking concentration, mass and volume.

Concentration = mass ÷ volume.

4.

Calculate the concentration of a solution containing 20 g of solute in 2 dm³.

Concentration = 20 ÷ 2 = 10 g/dm³.

5.

Calculate the mass of solute in 0.5 dm³ of a 10 g/dm³ solution.

Mass = concentration × volume = 10 × 0.5 = 5 g.

6.

Explain how increasing the amount of solute affects concentration.

Increasing the amount of solute increases the concentration if the volume stays the same.

4.3.3.1 Percentage Yield (Triple Only)

1.

What is meant by percentage yield?

Percentage yield compares the actual amount of product made with the maximum possible amount.

2.

Write the equation for percentage yield.

Percentage yield = (actual yield ÷ theoretical yield) × 100.

3.

Give one reason why the percentage yield may be less than 100%.

Reasons include incomplete reactions, product loss during separation or side reactions.

4.

What is the theoretical yield?

The theoretical yield is the maximum amount of product predicted from calculations.

5.

Calculate the percentage yield if the actual yield is 8 g and the theoretical yield is 10 g.

Percentage yield = (8 ÷ 10) × 100 = 80%.

6.

Explain why reactions rarely produce a 100% yield.

Reactions rarely produce 100% yield because products can be lost and reactions may not go to completion.

4.3.3.2 Atom Economy (Triple Only)

1.

What is atom economy?

Atom economy measures how much of the reactant atoms are converted into useful product.

2.

Why is a high atom economy desirable?

A high atom economy reduces waste and makes reactions more sustainable.

3.

Write the equation for atom economy.

Atom economy = (Mr of desired product ÷ total Mr of products) × 100.

4.

Calculate the atom economy for the production of iron from iron(III) oxide using the balanced equation: 2Fe₂O₃ + 3C → 4Fe + 3CO₂

Atom economy = (4 × 56) ÷ [(4 × 56) + (3 × 44)] × 100 = 63.6%.

5.

Calculate the atom economy for the production of magnesium oxide using the balanced equation: 2Mg + O₂ → 2MgO

Atom economy = (2 × 40) ÷ (2 × 40) × 100 = 100%.

6.

Explain why reactions with high atom economy are more sustainable.

High atom economy reactions are more sustainable because they produce less waste.

4.3.4 Using Concentrations of Solutions in mol/dm³ (Triple Higher Tier)

1.

What units are used for concentration in moles?

Concentration in moles is measured in mol/dm³.

2.

Write the equation linking concentration, moles and volume.

Concentration = moles ÷ volume.

3.

What unit must volume be in when using the concentration equation?

Volume must be measured in dm³.

4.

Calculate the number of moles in 0.5 dm³ of a 2 mol/dm³ solution.

Moles = concentration × volume = 2 × 0.5 = 1 mol.

5.

Calculate the concentration of a solution containing 1 mole in 0.25 dm³.

Concentration = 1 ÷ 0.25 = 4 mol/dm³.

6.

Explain how titration can be used to determine concentration.

Titration determines concentration by reacting a known volume of one solution with another of known concentration.

4.3.5 Use of Amount of Substance in Relation to Volumes of Gases (Triple Higher Tier)

1.

What volume does one mole of gas occupy at room temperature and pressure?

One mole of gas occupies 24 dm³ at room temperature and pressure.

2.

What conditions are assumed when using 24 dm³ per mole?

The conditions assumed are room temperature and pressure.

3.

Write the equation linking gas volume and moles.

Gas volume = moles × 24 dm³.

4.

Calculate the volume occupied by 2 moles of gas at room temperature.

Volume of 2 moles = 2 × 24 = 48 dm³.

5.

Calculate the number of moles in 48 dm³ of gas.

Moles in 48 dm³ = 48 ÷ 24 = 2 mol.

6.

Explain why equal numbers of moles of different gases occupy equal volumes under the same conditions.

Equal numbers of moles of gases occupy equal volumes because they contain the same number of particles under the same conditions.

Topic 3 Review

1.

State the law of conservation of mass.

The law of conservation of mass states that mass is conserved during chemical reactions.

2.

Write the equation used to calculate moles.

Moles = mass ÷ relative formula mass.

3.

Explain why balanced equations are needed in quantitative chemistry.

Balanced equations are needed because they show the correct ratios of reacting substances.

4.

State two reasons why percentage yield may be less than 100%.

Percentage yield may be less than 100% because of product loss and incomplete reactions.

5.

Explain the difference between percentage yield and atom economy.

Percentage yield measures the amount of product obtained compared with the maximum possible amount; atom economy measures how much of the reactant atoms become useful products.

6.

Describe how moles are used to calculate reacting masses and gas volumes.

Moles are used to calculate reacting masses and gas volumes by using mole ratios from balanced equations.

4.4.1.1 Metal Oxides

1.

What is produced when a metal reacts with oxygen?

A metal reacts with oxygen to produce a metal oxide.

2.

What is oxidation in terms of oxygen?

Oxidation is the gain of oxygen.

3.

What is reduction in terms of oxygen?

Reduction is the loss of oxygen.

4.

Why are reactions between metals and oxygen called oxidation reactions?

Reactions between metals and oxygen are called oxidation reactions because the metal gains oxygen.

5.

Which substance is reduced when copper oxide is heated with carbon?

Copper oxide is reduced when it is heated with carbon.

6.

Explain why oxidation and reduction occur together in reactions involving metal oxides.

Oxidation and reduction occur together because when one substance gains oxygen, another substance must lose oxygen.

4.4.1.2 The Reactivity Series

1.

What is the reactivity series?

The reactivity series is a list of metals arranged in order of their reactivity, from most reactive to least reactive.

2.

Which metal is more reactive: magnesium or copper?

Magnesium is more reactive than copper.

3.

What happens when a more reactive metal is added to a compound containing a less reactive metal?

A more reactive metal displaces a less reactive metal from its compound.

4.

Which non-metals are included in the reactivity series?

The non-metals included in the reactivity series are carbon and hydrogen.

5.

Put the following metals in order of reactivity from most to least reactive: iron, potassium, zinc, copper.

Potassium, iron, zinc, copper.

6.

Explain why potassium reacts more vigorously with water than magnesium.

Potassium reacts more vigorously with water than magnesium because potassium is higher in the reactivity series and loses electrons more easily.

4.4.1.3 Extraction of Metals and Reduction

1.

How are unreactive metals such as gold found in the Earth's crust?

Unreactive metals such as gold are found as the metal itself in the Earth’s crust.

2.

Which metals can be extracted from their oxides using carbon?

Metals below carbon in the reactivity series can be extracted from their oxides using carbon.

3.

What happens to oxygen during the reduction of a metal oxide?

Oxygen is removed from the metal oxide during reduction.

4.

Why is carbon used to extract some metals from their oxides?

Carbon is used because it is more reactive than some metals and can remove oxygen from their oxides.

5.

Why cannot aluminium be extracted from aluminium oxide using carbon?

Aluminium cannot be extracted using carbon because it is more reactive than carbon.

6.

Explain why the method used to extract a metal depends on its position in the reactivity series.

The extraction method depends on the reactivity series because more reactive metals require electrolysis, while less reactive metals can be extracted by reduction with carbon.

4.4.1.4 Oxidation and Reduction in Terms of Electrons (Higher Tier)

1.

What is oxidation in terms of electrons?

Oxidation is the loss of electrons.

2.

What is reduction in terms of electrons?

Reduction is the gain of electrons.

3.

Which species is oxidised in the reaction: Zn + Cu²⁺ → Zn²⁺ + Cu?

Zinc is oxidised in the reaction Zn + Cu²⁺ → Zn²⁺ + Cu.

4.

Which species is reduced in the reaction: Zn + Cu²⁺ → Zn²⁺ + Cu?

Copper ions (Cu²⁺) are reduced in the reaction Zn + Cu²⁺ → Zn²⁺ + Cu.

5.

Write the ionic equation for the reaction between magnesium and copper(II) sulfate solution.

Mg + Cu²⁺ → Mg²⁺ + Cu.

6.

Explain why displacement reactions are examples of redox reactions.

Displacement reactions are redox reactions because electrons are transferred between atoms and ions.

4.4.2.1 Reactions of Acids with Metals

1.

What gas is produced when an acid reacts with a metal?

Hydrogen gas is produced when an acid reacts with a metal.

2.

What type of salt is produced when magnesium reacts with hydrochloric acid?

Magnesium reacts with hydrochloric acid to produce magnesium chloride.

3.

What is the general word equation of a metal reacting with acid?

Metal + acid → salt + hydrogen.

4.

Write the word equation for the reaction between zinc and sulfuric acid.

Zinc + sulfuric acid → zinc sulfate + hydrogen.

5.

Which metal reacts more vigorously with dilute hydrochloric acid: magnesium or iron?

Magnesium reacts more vigorously with dilute hydrochloric acid than iron.

6.

Explain why reactions between acids and metals are redox reactions.

Acid-metal reactions are redox reactions because the metal loses electrons and hydrogen ions gain electrons.

4.4.2.2 Neutralisation of Acids and Salt Production

1.

What is produced when an acid reacts with an alkali?

An acid reacts with an alkali to produce salt and water.

2.

What is produced when an acid reacts with a metal carbonate?

An acid reacts with a metal carbonate to produce salt, water and carbon dioxide.

3.

Which acid is used to produce sulfate salts?

Sulfuric acid is used to produce sulfate salts.

4.

Which acid is used to produce nitrate salts?

Nitric acid is used to produce nitrate salts.

5.

What salt is produced when nitric acid reacts with potassium hydroxide?

Nitric acid + potassium hydroxide → potassium nitrate + water.

6.

Explain how the acid used determines the name of the salt produced.

The acid used determines the salt name because the acid’s negative ion becomes part of the salt.

4.4.2.3 Soluble Salts (Required Practical 1)

1.

Why is excess insoluble solid added when making a soluble salt?

Excess insoluble solid is added to ensure all the acid reacts.

2.

Why is the excess solid filtered from the solution when making a soluble salt?

Excess solid is filtered out to remove unreacted material.

3.

Why is the salt solution heated after filtration when making a soluble salt?

The salt solution is heated to evaporate some water and concentrate the solution.

4.

When making a soluble salt, why should the salt solution not be heated to complete dryness?

The solution should not be heated to complete dryness because crystals may decompose or become impure.

5.

Put the following steps in order: filtration, crystallisation, add excess solid, warm the acid.

Warm the acid → add excess solid → filtration → crystallisation.

6.

Explain the required practical of producing a pure, dry sample of a soluble salt.

Add excess insoluble base to warm acid, filter to remove excess solid, evaporate some water, allow crystals to form, then filter and dry the crystals.

4.4.2.4 The pH Scale and Neutralisation

1.

What is the pH of a neutral solution?

A neutral solution has a pH of 7.

2.

Which ions make a solution acidic?

Hydrogen ions (H⁺) make a solution acidic.

3.

Which ions make a solution alkaline?

Hydroxide ions (OH⁻) make a solution alkaline.

4.

What is produced when hydrogen ions react with hydroxide ions?

Hydrogen ions react with hydroxide ions to produce water.

5.

Which piece of equipment can be used to measure the approximate pH of a solution?

Universal indicator or a pH probe can be used to measure approximate pH.

6.

Explain why hydrochloric acid and sodium hydroxide produce a neutral solution when they react in the correct proportions.

Hydrochloric acid and sodium hydroxide produce a neutral solution because H⁺ ions react with OH⁻ ions to form water.

4.4.2.5 Titrations (Required Practical 2 - Chemistry Only)

1.

What is the purpose of a titration?

The purpose of a titration is to find the exact volume of one solution needed to react with another.

2.

Which piece of apparatus is used to deliver the acid accurately during a titration?

A burette is used to deliver acid accurately.

3.

What is the end point of a titration?

The end point is when the indicator changes colour.

4.

Why is a suitable indicator added during a titration?

An indicator is added to show when neutralisation is complete.

5.

Calculate the mean titre for the following concordant results: 24.60 cm³, 24.70 cm³ and 24.65 cm³.

Mean titre = (24.60 + 24.70 + 24.65) ÷ 3 = 24.65 cm³.

6.

Explain why concordant titres are used when calculating the mean titre.

Concordant titres are used because they are close together and give a reliable mean result.

4.4.2.6 Strong and Weak Acids (Higher Tier)

1.

What is a strong acid?

A strong acid completely ionises in water.

2.

What is a weak acid?

A weak acid only partially ionises in water.

3.

Which has the lower pH at the same concentration: a strong acid or a weak acid?

A strong acid has a lower pH at the same concentration.

4.

What is the difference between a concentrated acid and a dilute acid?

A concentrated acid contains a large amount of acid per volume; a dilute acid contains less acid per volume.

5.

By what factor does the hydrogen ion concentration increase when pH decreases from 5 to 3?

Hydrogen ion concentration increases by 100 times when pH decreases from 5 to 3.

6.

Explain why a dilute hydrochloric acid can be a stronger acid than a concentrated ethanoic acid.

A dilute hydrochloric acid can be stronger because it completely ionises, while concentrated ethanoic acid only partially ionises.

4.4.3.1 The Process of Electrolysis

1.

What is an electrolyte?

An electrolyte is a substance containing ions that can move and conduct electricity.

2.

Which electrode is the cathode?

The cathode is the negative electrode.

3.

Which ions move towards the cathode during electrolysis?

Positive ions move towards the cathode.

4.

Which ions move towards the anode during electrolysis?

Negative ions move towards the anode.

5.

Why must an ionic compound be molten or dissolved before it can be electrolysed?

Ionic compounds must be molten or dissolved so ions are free to move.

6.

Explain why electrolysis causes elements to be produced at the electrodes.

Electrolysis produces elements because ions gain or lose electrons at the electrodes.

4.4.3.2 Electrolysis of Molten Ionic Compounds

1.

What is produced at the cathode during the electrolysis of molten lead bromide?

Lead is produced at the cathode during electrolysis of molten lead bromide.

2.

What is produced at the anode during the electrolysis of molten lead bromide?

Bromine is produced at the anode during electrolysis of molten lead bromide.

3.

Why are inert electrodes used during electrolysis?

Inert electrodes are used because they do not react with the products.

4.

Predict the products formed during the electrolysis of molten zinc chloride.

Molten zinc chloride produces zinc at the cathode and chlorine at the anode.

5.

Write the formula of the substance produced at the anode during the electrolysis of molten sodium chloride.

Chlorine (Cl₂) is produced at the anode during molten sodium chloride electrolysis.

6.

Explain why molten ionic compounds conduct electricity.

Molten ionic compounds conduct electricity because ions are free to move and carry charge.

4.4.3.3 Using Electrolysis to Extract Metals

1.

Which metals are extracted using electrolysis?

Metals above carbon in the reactivity series are extracted using electrolysis.

2.

Why is aluminium extracted by electrolysis instead of using carbon?

Aluminium is extracted by electrolysis because it is more reactive than carbon.

3.

Why is cryolite mixed with aluminium oxide during electrolysis?

Cryolite lowers the melting point of aluminium oxide.

4.

Why must the carbon anodes be replaced regularly during aluminium extraction?

Carbon anodes are replaced because they react with oxygen to form carbon dioxide.

5.

Which electrode produces aluminium during electrolysis?

Aluminium is produced at the cathode.

6.

Explain why extracting aluminium by electrolysis is expensive.

Extracting aluminium is expensive because electrolysis requires large amounts of electricity.

4.4.3.4 Electrolysis of Aqueous Solutions (Required Practical 3)

1.

What is produced at the cathode when aqueous copper(II) sulfate is electrolysed using inert electrodes?

Copper is produced at the cathode when aqueous copper(II) sulfate is electrolysed using inert electrodes.

2.

What is produced at the anode when aqueous sodium chloride is electrolysed using inert electrodes?

Chlorine gas is produced at the anode when aqueous sodium chloride is electrolysed.

3.

Which gas is produced at the cathode if the metal is more reactive than hydrogen?

Hydrogen is produced at the cathode if the metal is more reactive than hydrogen.

4.

Which gas is usually produced at the anode if no halide ions are present?

Oxygen is usually produced at the anode if no halide ions are present.

5.

Predict the products formed during the electrolysis of aqueous potassium chloride using inert electrodes.

Aqueous potassium chloride produces hydrogen at the cathode and chlorine at the anode.

6.

Explain how the reactivity series helps predict the products of electrolysis in aqueous solutions.

The reactivity series helps predict whether a metal or hydrogen will be produced at the cathode.

4.4.3.5 Representation of Reactions at Electrodes as Half Equations (Higher Tier)

1.

What happens to positive ions at the cathode during electrolysis?

Positive ions gain electrons at the cathode.

2.

What happens to negative ions at the anode during electrolysis?

Negative ions lose electrons at the anode.

3.

Write the half equation for the formation of hydrogen from hydrogen ions.

2H⁺ + 2e⁻ → H₂.

4.

Write the half equation for the formation of chlorine from chloride ions.

2Cl⁻ → Cl₂ + 2e⁻.

5.

Write the half equation for the formation of copper from Cu²⁺ ions.

Cu²⁺ + 2e⁻ → Cu.

6.

Explain why reduction occurs at the cathode and oxidation occurs at the anode.

Reduction occurs at the cathode because ions gain electrons, and oxidation occurs at the anode because ions lose electrons.

Topic 4 Review

1.

What is the difference between oxidation and reduction in terms of oxygen?

Oxidation is gain of oxygen and reduction is loss of oxygen.

2.

Explain why metals above carbon in the reactivity series cannot be extracted using carbon.

Metals above carbon cannot be extracted using carbon because they are more reactive and their oxides are too stable.

3.

State the products formed when an acid reacts with a metal carbonate.

Acid + metal carbonate produces salt, water and carbon dioxide.

4.

Describe how a pure, dry sample of a soluble salt is prepared from an insoluble base.

Add excess insoluble base to acid, filter, evaporate some water, crystallise and dry the soluble salt.

5.

Explain why molten ionic compounds conduct electricity but solid ionic compounds do not.

Molten ionic compounds conduct electricity because ions can move; solid ionic compounds do not because ions are fixed.

6.

Compare the products formed during the electrolysis of molten sodium chloride and aqueous sodium chloride.

Molten sodium chloride produces sodium and chlorine, while aqueous sodium chloride produces hydrogen and chlorine because water affects which ions are discharged.

4.5.1.1 Energy Transfer During Exothermic and Endothermic Reactions

1.

What is an exothermic reaction?

An exothermic reaction is a reaction that transfers energy to the surroundings, usually as heat.

2.

What is an endothermic reaction?

An endothermic reaction is a reaction that takes in energy from the surroundings.

3.

Name one example of an exothermic reaction.

Combustion is an example of an exothermic reaction.

4.

Name one example of an endothermic reaction.

Thermal decomposition is an example of an endothermic reaction.

5.

What happens to the temperature of the surroundings during an endothermic reaction?

The temperature of the surroundings decreases during an endothermic reaction.

6.

Explain why the products of an exothermic reaction have less energy than the reactants.

The products of an exothermic reaction have less energy than the reactants because more energy is released when bonds form than is needed to break bonds.

Required Practical 4: Investigating Temperature Changes

1.

What is measured during the required practical investigating temperature changes in reacting solutions?

The temperature change of reacting solutions is measured.

2.

Why is a lid placed on the reaction cup during the required practical investigating temperature changes?

A lid is placed on the reaction cup to reduce heat loss to the surroundings.

3.

Why should the reactants be mixed quickly during the required practical investigating temperature changes?

Reactants should be mixed quickly to ensure the reaction starts at the same time and the maximum temperature change is recorded.

4.

Why should the same volumes of reactants be used when comparing temperature changes in different reactions?

The same volumes of reactants should be used to make a fair comparison.

5.

Why are repeat measurements carried out during the required practical investigating temperature changes?

Repeat measurements are carried out to improve reliability and calculate a mean result.

6.

Explain why reducing heat loss improves the accuracy of the required practical investigating temperature changes.

Reducing heat loss improves accuracy because more of the energy change is measured rather than being lost to the surroundings.

4.5.1.2 Reaction Profiles

1.

What is activation energy?

Activation energy is the minimum energy needed for a reaction to occur.

2.

What does a reaction profile show?

A reaction profile shows the energy changes during a chemical reaction, including activation energy and overall energy change.

3.

Draw a labelled reaction profile for the endothermic reaction A + B → C + D, showing the reactants, products, activation energy and overall energy change.

In an endothermic reaction profile, the products are at a higher energy level than the reactants, with a positive overall energy change.

4.

Draw a labelled reaction profile for the exothermic reaction A + B → C + D, showing the reactants, products, activation energy and overall energy change.

In an exothermic reaction profile, the products are at a lower energy level than the reactants, with a negative overall energy change.

5.

What does the highest point on a reaction profile represent?

The highest point on a reaction profile represents the activated complex and the activation energy level.

6.

Explain why all chemical reactions require activation energy.

All chemical reactions require activation energy because bonds must be broken before new bonds can form.

4.5.1.3 The Energy Change of Reactions (Higher Tier)

1.

What happens to energy when chemical bonds are broken?

Energy is needed to break chemical bonds.

2.

What happens to energy when new chemical bonds are formed?

Energy is released when new chemical bonds are formed.

3.

In an exothermic reaction, is more energy released from bond formation or needed to break bonds?

In an exothermic reaction, more energy is released during bond formation than is needed to break bonds.

4.

In an endothermic reaction, is more energy needed to break bonds or released from bond formation?

In an endothermic reaction, more energy is needed to break bonds than is released during bond formation.

5.

Calculate the overall energy change for a reaction if 820 kJ is needed to break bonds and 950 kJ is released when new bonds are formed.

Energy change = energy needed to break bonds − energy released when bonds form = 820 − 950 = −130 kJ.

6.

Explain why bond breaking and bond making occur together during a chemical reaction.

Bond breaking and bond making occur together because atoms must separate before rearranging into new substances.

4.5.2.1 Cells and Batteries (Chemistry Only)

1.

What produces electricity in a chemical cell?

Electricity is produced in a chemical cell by chemical reactions transferring electrons.

2.

How can a simple chemical cell be made?

A simple chemical cell can be made using two different metals and an electrolyte.

3.

What is the difference between a cell and a battery?

A cell is a single unit that produces electricity; a battery is two or more cells connected together.

4.

Why do non-rechargeable batteries eventually stop working?

Non-rechargeable batteries stop working because the chemicals inside are used up.

5.

Why can rechargeable batteries be used many times?

Rechargeable batteries can be used many times because the chemical reactions can be reversed.

6.

Explain why connecting cells in series increases the voltage of a battery.

Connecting cells in series increases voltage because the voltages of the cells add together.

4.5.2.2 Fuel Cells (Chemistry Only)

1.

What fuel is used in a hydrogen fuel cell?

Hydrogen is the fuel used in a hydrogen fuel cell.

2.

What is the overall product formed in a hydrogen fuel cell?

The overall product formed is water.

3.

Where does the oxygen used in a hydrogen fuel cell come from?

Oxygen comes from the air.

4.

How is hydrogen converted into electrical energy in a hydrogen fuel cell?

Hydrogen reacts with oxygen in the fuel cell, transferring electrons through an external circuit to produce electricity.

5.

State one advantage of hydrogen fuel cells compared with rechargeable batteries.

An advantage is that hydrogen fuel cells only produce water, so they do not release carbon dioxide during operation.

6.

Explain one disadvantage of using hydrogen fuel cells compared with rechargeable batteries.

A disadvantage is that hydrogen is difficult and expensive to store and transport.

Topic 5 Review

1.

What is the difference between an exothermic reaction and an endothermic reaction?

An exothermic reaction releases energy to the surroundings, while an endothermic reaction absorbs energy from the surroundings.

2.

Explain why combustion reactions are exothermic.

Combustion reactions are exothermic because forming products such as carbon dioxide and water releases more energy than is required to break the fuel bonds.

3.

Describe how a reaction profile for an endothermic reaction differs from a reaction profile for an exothermic reaction.

An endothermic reaction profile has products at a higher energy level than reactants, while an exothermic profile has products at a lower energy level.

4.

Explain why energy is required to break chemical bonds.

Energy is required to break bonds because energy is needed to overcome the forces holding atoms together.

5.

Compare rechargeable batteries with hydrogen fuel cells.

Rechargeable batteries can be reused because their reactions are reversible, while hydrogen fuel cells continuously produce electricity while supplied with hydrogen and oxygen.

6.

Explain how the breaking and formation of chemical bonds determine whether a reaction is exothermic or endothermic.

A reaction is exothermic when more energy is released making bonds than is used breaking bonds, and endothermic when more energy is needed to break bonds than is released forming them.

4.6.1.1 Calculating Rates of Reactions

1.

What is meant by the rate of a chemical reaction?

The rate of a chemical reaction is the amount of reactant used or product formed per unit of time.

2.

How is the mean rate of reaction calculated using the quantity of reactant used?

Mean rate = quantity of reactant used ÷ time taken.

3.

How is the mean rate of reaction calculated using the quantity of product formed?

Mean rate = quantity of product formed ÷ time taken.

4.

What units can be used for the rate of reaction when measuring mass change?

Units for rate when measuring mass change include g/s or g/min.

5.

How can a graph showing product formed against time be used to determine the rate of reaction?

A graph of product formed against time can be used by calculating the gradient; a steeper gradient shows a faster reaction.

6.

How can the gradient of a tangent to a reaction graph be used to calculate the rate of reaction at a specific time?

The gradient of a tangent gives the rate at a specific time by calculating change in amount ÷ change in time.

4.6.1.2 Factors Which Affect the Rates of Chemical Reactions

1.

What five factors can affect the rate of a chemical reaction?

The five factors are temperature, concentration, pressure, surface area and catalysts.

2.

How does increasing the concentration of reactants in solution affect the rate of reaction?

Increasing concentration increases the rate because there are more reacting particles in the same volume, causing more frequent collisions.

3.

How does decreasing the pressure of reacting gases affect the rate of reaction?

Decreasing pressure of reacting gases decreases the rate because gas particles are further apart and collide less often.

4.

How does increasing the surface area of a solid reactant affect the rate of reaction?

Increasing surface area increases the rate because more particles are exposed and collisions happen more frequently.

5.

How does increasing the temperature affect the rate of a chemical reaction?

Increasing temperature increases the rate because particles move faster and more collisions have enough energy to react.

6.

How does the presence of a catalyst affect the rate of a chemical reaction?

A catalyst increases the rate by providing an alternative pathway with a lower activation energy.

Required Practical 5: Investigating How Changes in Concentration Affect the Rates of Reactions

1.

What is measured when investigating how changes in concentration affect the rate of reaction using gas production?

The volume of gas produced is measured when investigating reaction rate using gas production.

2.

Why can the volume of gas produced be used to measure the rate of reaction?

Gas volume can be used to measure rate because faster reactions produce gas more quickly.

3.

What variable is changed when investigating the effect of concentration on reaction rate?

The concentration of a reactant is changed.

4.

Why should only one variable be changed when investigating the effect of concentration on reaction rate?

Only one variable should be changed to make the investigation a fair test.

5.

Why are repeat measurements carried out when investigating the effect of concentration on reaction rate?

Repeat measurements are carried out to improve reliability and calculate a mean.

6.

Why should a hypothesis be made before carrying out an investigation into reaction rates?

A hypothesis is made before the investigation to predict the expected relationship between variables.

4.6.1.3 Collision Theory and Activation Energy

1.

What does collision theory state about chemical reactions?

Collision theory states that particles must collide with enough energy and the correct orientation for a reaction to occur.

2.

Why must reacting particles collide for a chemical reaction to occur?

Reacting particles must collide to allow bonds to break and new bonds to form.

3.

What is activation energy?

Activation energy is the minimum energy needed for successful collisions.

4.

How does increasing the concentration of reactants increase the rate of reaction according to collision theory?

Increasing concentration increases reaction rate because there are more particles, causing more frequent successful collisions.

5.

How does increasing temperature increase the rate of reaction according to collision theory?

Increasing temperature increases reaction rate because particles move faster and more collisions have enough activation energy.

6.

Why does increasing the surface area of a solid reactant increase the rate of reaction?

Increasing surface area increases reaction rate because more particles are exposed, causing more frequent collisions.

4.6.1.4 Catalysts

1.

What is a catalyst?

A catalyst is a substance that increases the rate of a reaction without being used up.

2.

Why are catalysts not used up during a chemical reaction?

Catalysts are not used up because they are unchanged at the end of the reaction.

3.

How do catalysts increase the rate of a chemical reaction?

Catalysts increase reaction rate by providing an alternative reaction pathway with lower activation energy.

4.

What happens to the activation energy when a catalyst is used?

The activation energy decreases when a catalyst is used.

5.

Why do different chemical reactions require different catalysts?

Different reactions require different catalysts because catalysts work by specific interactions with reactants.

6.

How can catalysts be identified from a chemical equation and reaction rate?

Catalysts can be identified because they appear unchanged in the chemical equation and increase reaction rate.

4.6.2.1 Reversible Reactions

1.

What is a reversible reaction?

A reversible reaction is a reaction where products can react to form the original reactants.

2.

How are reversible reactions represented using a symbol equation?

Reversible reactions are represented using the symbol ⇌.

3.

What happens in a reversible reaction when products react to form reactants?

Products react to form reactants in the reverse reaction.

4.

How can the direction of a reversible reaction be changed?

The direction can be changed by altering conditions such as temperature, pressure or concentration.

5.

What is meant by the forward reaction in a reversible reaction?

The forward reaction is the reaction that forms products from reactants.

6.

What is meant by the reverse reaction in a reversible reaction?

The reverse reaction is the reaction that forms reactants from products.

4.6.2.2 Energy Changes and Reversible Reactions

1.

What type of reaction is the reverse of an exothermic reaction?

The reverse of an exothermic reaction is endothermic.

2.

What happens to energy when an exothermic reaction is reversed?

When an exothermic reaction is reversed, energy is absorbed.

3.

How much energy is transferred in each direction of a reversible reaction?

The same amount of energy is transferred in each direction but in opposite ways.

4.

Why is the forward and reverse reaction in a reversible reaction linked by energy changes?

Forward and reverse reactions are linked because reversing a reaction reverses its energy change.

5.

What type of energy change occurs when an endothermic reaction is reversed?

The reverse of an endothermic reaction is exothermic.

6.

Explain why a reversible reaction can be both exothermic and endothermic.

A reversible reaction can be both exothermic and endothermic because the forward and reverse reactions have opposite energy changes.

4.6.2.3 Equilibrium

1.

What is meant by equilibrium in a reversible reaction?

Equilibrium is reached when the forward and reverse reactions occur at the same rate.

2.

What conditions are needed for equilibrium to be reached?

Equilibrium requires a closed system and constant conditions.

3.

Why must a reversible reaction be carried out in a closed system to reach equilibrium?

A reversible reaction must be in a closed system so reactants and products cannot escape.

4.

What happens to the forward reaction rate and reverse reaction rate at equilibrium?

At equilibrium, the forward and reverse reaction rates are equal.

5.

Why do the concentrations of reactants and products remain constant at equilibrium?

Concentrations remain constant because the amounts of reactants and products are no longer changing overall.

6.

Explain why equilibrium is described as a dynamic process.

Equilibrium is described as dynamic because reactions continue happening even though concentrations stay constant.

4.6.2.4 The Effect of Changing Conditions on Equilibrium (HT Only)

1.

What does Le Chatelier’s Principle state?

Le Chatelier’s Principle states that if conditions are changed, the equilibrium position shifts to oppose the change.

2.

What happens to an equilibrium system when a change is made to its conditions?

An equilibrium system responds by moving in the direction that reduces the effect of the change.

3.

Why does a system at equilibrium respond when a condition is changed?

The system responds because it tries to restore equilibrium.

4.

What factors can be changed to affect the position of equilibrium?

Temperature, pressure and concentration can affect equilibrium.

5.

How can Le Chatelier’s Principle be used to predict changes in equilibrium?

Le Chatelier’s Principle predicts the direction equilibrium will shift after a change.

6.

Why does an equilibrium system shift to counteract a change?

The system shifts to counteract a change by increasing the reaction that removes the effect of the change.

4.6.2.5 The Effect of Changing Concentration (HT Only)

1.

What happens when the concentration of a reactant is increased in an equilibrium system?

Increasing reactant concentration shifts equilibrium towards the products.

2.

Why does increasing the concentration of a reactant produce more products?

More reactant particles cause more collisions, increasing the forward reaction rate.

3.

What happens when the concentration of a product is decreased in an equilibrium system?

Decreasing product concentration shifts equilibrium towards the products.

4.

Why do concentrations of all substances change after the concentration of one substance is altered?

All concentrations change because the system adjusts until equilibrium is restored.

5.

How can changing concentration affect the position of equilibrium?

Changing concentration affects the position of equilibrium by favouring the reaction that removes the change.

6.

For the equilibrium reaction N₂(g) + 3H₂(g) ⇌ 2NH₃(g), explain what happens to the position of equilibrium when the concentration of hydrogen is increased.

For N₂(g) + 3H₂(g) ⇌ 2NH₃(g), increasing hydrogen concentration shifts equilibrium to the right, producing more ammonia.

4.6.2.6 The Effect of Temperature Changes on Equilibrium (HT Only)

1.

What happens to the amount of products at equilibrium when the temperature is increased for an endothermic reaction?

Increasing temperature in an endothermic reaction increases the amount of products.

2.

What happens to the amount of products at equilibrium when the temperature is increased for an exothermic reaction?

Increasing temperature in an exothermic reaction decreases the amount of products.

3.

What happens to the amount of products at equilibrium when the temperature is decreased for an endothermic reaction?

Decreasing temperature in an endothermic reaction decreases the amount of products.

4.

What happens to the amount of products at equilibrium when the temperature is decreased for an exothermic reaction?

Decreasing temperature in an exothermic reaction increases the amount of products.

5.

Why does increasing temperature affect the position of equilibrium?

Increasing temperature affects equilibrium because the system shifts to absorb or release heat.

6.

For the (exothermic) equilibrium reaction N₂(g) + 3H₂(g) ⇌ 2NH₃(g), predict how increasing the temperature affects the equilibrium position and explain why.

For the exothermic reaction N₂ + 3H₂ ⇌ 2NH₃, increasing temperature shifts equilibrium left because the reverse reaction absorbs heat.

4.6.2.7 The Effect of Pressure Changes on Equilibrium (HT Only)

1.

How does increasing pressure affect the equilibrium position of a gaseous reaction?

Increasing pressure shifts equilibrium towards the side with fewer gas molecules.

2.

Why does increasing pressure shift equilibrium towards the side with fewer gas molecules?

The equilibrium shifts to fewer gas molecules because this reduces pressure.

3.

How does decreasing pressure affect the equilibrium position of a gaseous reaction?

Decreasing pressure shifts equilibrium towards the side with more gas molecules.

4.

Why does decreasing pressure shift equilibrium towards the side with more gas molecules?

The equilibrium shifts to more gas molecules because this increases pressure.

5.

How can the symbol equation be used to predict the effect of pressure changes on equilibrium?

The symbol equation shows the number of gas molecules on each side and predicts pressure effects.

6.

For the equilibrium reaction N₂(g) + 3H₂(g) ⇌ 2NH₃(g), predict how increasing the pressure affects the equilibrium position and explain why.

For N₂(g) + 3H₂(g) ⇌ 2NH₃(g), increasing pressure shifts equilibrium right because there are fewer gas molecules on the product side.

Topic 6 Review

1.

How is the mean rate of reaction calculated?

Mean rate of reaction = quantity of reactant used or product formed ÷ time taken.

2.

Explain how concentration, pressure, surface area and temperature affect the rate of a chemical reaction.

Increasing concentration, pressure, surface area and temperature increases reaction rate; catalysts also increase rate.

3.

Explain how collision theory explains the effect of temperature on reaction rate.

Collision theory explains temperature effects because higher temperature gives particles more energy and increases successful collisions.

4.

Explain how catalysts increase the rate of reaction without being used up.

Catalysts increase rate by lowering activation energy and are not used up.

5.

What is the difference between a reversible reaction and a reaction that goes to completion?

A reversible reaction can go in both directions, while a reaction that goes to completion only forms products.

6.

Explain how changing concentration, temperature and pressure affects the position of equilibrium.

Changing concentration, temperature and pressure shifts equilibrium in the direction that opposes the change according to Le Chatelier’s Principle.

4.7.1.1 Crude Oil, Hydrocarbons and Alkanes

1.

What is crude oil?

Crude oil is a mixture of hydrocarbons found underground.

2.

Why is crude oil described as a finite resource?

Crude oil is described as a finite resource because it is non-renewable and will eventually run out.

3.

What are hydrocarbons?

Hydrocarbons are compounds made only of hydrogen and carbon atoms.

4.

What is the general formula for alkanes?

The general formula for alkanes is CₙH₂ₙ₊₂.

5.

What are the names of the first four alkanes?

The first four alkanes are methane, ethane, propane and butane.

6.

A hydrocarbon has the formula C₅H₁₂. Explain why this compound is an alkane.

C₅H₁₂ is an alkane because it follows the alkane general formula CₙH₂ₙ₊₂.

4.7.1.2 Fractional Distillation and Petrochemicals

1.

What is fractional distillation used to separate?

Fractional distillation is used to separate the hydrocarbons in crude oil.

2.

How does fractional distillation separate the hydrocarbons in crude oil?

It separates hydrocarbons because they have different boiling points.

3.

Why do different fractions condense at different temperatures during fractional distillation?

Different fractions condense at different temperatures because they contain hydrocarbons with different chain lengths.

4.

What are the main uses of fractions obtained from crude oil?

Fractions are used as fuels, lubricants and chemical feedstocks.

5.

What is meant by a petrochemical?

A petrochemical is a chemical product made from hydrocarbons obtained from crude oil.

6.

Explain why crude oil is an important feedstock for the petrochemical industry.

Crude oil is an important feedstock because it provides hydrocarbons used to make many useful chemicals and materials.

4.7.1.3 Properties of Hydrocarbons

1.

How does boiling point change as the size of hydrocarbon molecules increases?

Boiling point increases as hydrocarbon molecule size increases.

2.

How does viscosity change as the size of hydrocarbon molecules increases?

Viscosity increases as hydrocarbon molecule size increases.

3.

How does flammability change as the size of hydrocarbon molecules increases?

Flammability decreases as hydrocarbon molecule size increases.

4.

Why are hydrocarbons used as fuels?

Hydrocarbons are used as fuels because they release energy when burned.

5.

What are the products of the complete combustion of a hydrocarbon?

Complete combustion of a hydrocarbon produces carbon dioxide and water.

6.

Write the balanced symbol equation for the complete combustion of methane (CH₄).

CH₄ + 2O₂ → CO₂ + 2H₂O.

4.7.1.4 Cracking and Alkenes

1.

What is cracking?

Cracking is the process of breaking long-chain hydrocarbons into shorter-chain hydrocarbons.

2.

Why are hydrocarbons cracked?

Hydrocarbons are cracked to produce more useful shorter hydrocarbons and alkenes.

3.

What conditions are used for catalytic cracking?

Catalytic cracking uses a high temperature, a catalyst and often a high pressure.

4.

What type of hydrocarbon is produced alongside alkanes during cracking?

Alkenes are produced alongside alkanes during cracking.

5.

What colour change occurs when bromine water reacts with an alkene?

Bromine water changes from orange/brown to colourless when it reacts with an alkene.

6.

Balance the equation for the cracking of C₁₀H₂₂ to produce C₈H₁₈ and C₂H₄.

C₁₀H₂₂ → C₈H₁₈ + C₂H₄.

4.7.2.1 Structure and Formulae of Alkenes

1.

What is the functional group of alkenes?

The functional group of alkenes is the carbon-carbon double bond (C=C).

2.

What is the general formula for alkenes?

The general formula for alkenes is CₙH₂ₙ.

3.

Why are alkenes described as unsaturated hydrocarbons?

Alkenes are unsaturated because they contain a carbon-carbon double bond.

4.

What are the names of the first four alkenes?

The first four alkenes are ethene, propene, butene and pentene.

5.

How can an alkene be identified from its formula?

An alkene can be identified from its formula because it follows the CₙH₂ₙ pattern.

6.

A compound has the formula C₄H₈. Explain why this compound could be an alkene.

C₄H₈ could be an alkene because it follows the general formula CₙH₂ₙ.

4.7.2.2 Reactions of Alkenes

1.

Why are alkenes more reactive than alkanes?

Alkenes are more reactive than alkanes because the double bond can break and allow atoms to add.

2.

What happens when an alkene reacts with hydrogen?

An alkene reacts with hydrogen to form an alkane.

3.

What conditions are needed for hydrogen to react with an alkene?

Hydrogen reacts with alkenes using a nickel catalyst and heat.

4.

What happens when an alkene reacts with a halogen such as bromine?

An alkene reacts with a halogen to form a dihaloalkane.

5.

What happens to the carbon-carbon double bond during addition reactions?

The carbon-carbon double bond breaks during addition reactions.

6.

Complete the equation for the reaction between ethene and hydrogen: C₂H₄ + H₂ → ?

C₂H₄ + H₂ → C₂H₆.

4.7.2.3 Alcohols

1.

What is the functional group of alcohols?

The functional group of alcohols is the hydroxyl group (-OH).

2.

What are the names of the first four alcohols?

The first four alcohols are methanol, ethanol, propanol and butanol.

3.

What happens when ethanol burns in oxygen?

Ethanol burns in oxygen to produce carbon dioxide and water.

4.

What happens when alcohols react with sodium?

Alcohols react with sodium to produce hydrogen gas and a salt.

5.

What conditions are needed for the fermentation of sugar to produce ethanol?

Fermentation requires yeast, a sugar solution and a warm temperature without oxygen.

6.

Write the balanced symbol equation for the complete combustion of ethanol (C₂H₅OH).

C₂H₅OH + 3O₂ → 2CO₂ + 3H₂O.

4.7.2.4 Carboxylic Acids

1.

What is the functional group of carboxylic acids?

The functional group of carboxylic acids is -COOH.

2.

What are the names of the first four carboxylic acids?

The first four carboxylic acids are methanoic acid, ethanoic acid, propanoic acid and butanoic acid.

3.

What happens when carboxylic acids react with carbonates?

Carboxylic acids react with carbonates to produce salt, water and carbon dioxide.

4.

Why do carboxylic acids dissolve in water?

Carboxylic acids dissolve in water because they can form hydrogen bonds with water molecules.

5.

What type of reaction occurs when a carboxylic acid reacts with an alcohol?

A carboxylic acid reacting with an alcohol is an esterification reaction.

6.

Explain why carboxylic acids are weak acids in terms of ionisation. (HT only)

Carboxylic acids are weak acids because they only partially ionise in water.

4.7.3.1 Addition Polymerisation

1.

What is a polymer?

A polymer is a large molecule made from many repeating units.

2.

What is a monomer?

A monomer is a small molecule that joins with other monomers to form a polymer.

3.

What type of monomers are used in addition polymerisation?

Addition polymerisation uses monomers containing carbon-carbon double bonds.

4.

What happens to the carbon-carbon double bond during addition polymerisation?

The carbon-carbon double bond opens and monomers join together.

5.

Why does an addition polymer have the same atoms as its monomer?

Addition polymers contain the same atoms as their monomers because no atoms are lost.

6.

Draw the repeating unit formed from the monomer ethene.

Ethene forms poly(ethene) with the repeating unit –CH₂–CH₂–.

4.7.3.2 Condensation Polymerisation (HT Only)

1.

What type of monomers are needed for condensation polymerisation?

Condensation polymerisation requires monomers with two functional groups.

2.

Why are condensation polymerisation reactions different from addition polymerisation reactions?

Condensation polymerisation produces a small molecule, usually water, unlike addition polymerisation.

3.

What small molecule is usually produced during condensation polymerisation?

Water is usually produced during condensation polymerisation.

4.

Draw the displayed formula equation showing the condensation polymerisation reaction between propanediol and butanedioic acid, including the monomers, the ester link formed, and the repeating unit of the polyester produced.

Propanediol and butanedioic acid form a polyester by joining through ester links.

5.

How are polyesters formed from two different monomers?

Polyesters are formed when monomers join and release small molecules such as water.

6.

Explain how ethanediol and hexanedioic acid form a polyester by condensation polymerisation.

Ethanediol and hexanedioic acid form a polyester through ester bonds formed between hydroxyl and carboxyl groups.

4.7.3.3 Amino Acids (HT Only)

1.

What two functional groups are present in amino acids?

Amino acids contain an amine group (-NH₂) and a carboxylic acid group (-COOH).

2.

What type of polymer is formed when amino acids join together?

Amino acids form proteins.

3.

What type of reaction joins amino acids together?

Amino acids join together by condensation polymerisation.

4.

What small molecule is produced when amino acids polymerise?

Water is produced when amino acids polymerise.

5.

What is the formula of glycine?

The formula of glycine is NH₂CH₂COOH.

6.

Explain how different amino acids can combine to form different proteins.

Different amino acids combine in different sequences to form different proteins.

4.7.3.4 DNA and Other Naturally Occurring Polymers

1.

What is DNA?

DNA is a polymer that carries genetic information.

2.

What are the monomers that make up DNA?

The monomers of DNA are nucleotides.

3.

What shape is the structure of most DNA molecules?

DNA has a double helix structure.

4.

What information does DNA encode?

DNA encodes genetic information used to make proteins.

5.

What are the monomers that make up proteins?

The monomers of proteins are amino acids.

6.

Name the monomers from which starch and cellulose are made.

Starch and cellulose are made from glucose monomers.

Topic 7 Review

1.

What is the difference between alkanes and alkenes?

Alkanes are saturated hydrocarbons with single bonds, while alkenes are unsaturated hydrocarbons containing a C=C double bond.

2.

Explain how fractional distillation separates crude oil into useful fractions.

Fractional distillation separates crude oil because hydrocarbons have different boiling points.

3.

Write the balanced symbol equation for the complete combustion of a hydrocarbon.

Hydrocarbon combustion: hydrocarbon + oxygen → carbon dioxide + water.

4.

Explain why cracking is used to produce more useful hydrocarbons.

Cracking produces more useful hydrocarbons by converting long-chain molecules into shorter alkanes and alkenes.

5.

Compare addition polymerisation with condensation polymerisation.

Addition polymerisation uses one type of alkene monomer and produces no small molecule; condensation polymerisation uses two monomers and releases a small molecule.

6.

Explain how carbon atoms can form a wide range of organic compounds.

Carbon atoms can form many organic compounds because they can form four strong covalent bonds and bond with other carbon atoms to make chains and rings.

4.8.1.1 Pure Substances

1.

What is meant by a pure substance in chemistry?

A pure substance contains only one element or one compound.

2.

What is the difference between a pure substance and a mixture?

A pure substance has fixed composition, while a mixture contains two or more substances not chemically bonded.

3.

Why do pure substances have specific melting points and boiling points?

Pure substances have specific melting and boiling points because they contain particles with the same strength of attraction.

4.

How can melting point data be used to identify an impure substance?

An impure substance melts over a range of temperatures and usually has a lower melting point.

5.

How can boiling point data be used to distinguish pure substances from mixtures?

Boiling point data can show whether a substance is pure because a pure substance boils at a fixed temperature.

6.

A substance melts over a range of temperatures rather than at one fixed temperature. Explain what this suggests about the substance.

A substance melting over a range of temperatures suggests it is impure.

4.8.1.2 Formulations

1.

What is a formulation?

A formulation is a mixture designed as a useful product with specific quantities of components.

2.

Why are formulations made by mixing components in carefully measured quantities?

Formulations are made with carefully measured quantities so they have the required properties.

3.

Name three examples of products that are formulations.

Examples include fuels, medicines and paints.

4.

Why does each chemical in a formulation have a specific purpose?

Each chemical in a formulation has a specific purpose, such as improving colour, stability or effectiveness.

5.

How can a formulation be identified from information about its components?

A formulation can be identified because it contains several substances with specific functions.

6.

Explain why a paint is considered a formulation rather than a pure substance.

Paint is a formulation because it contains pigments, solvents and other substances mixed in specific amounts.

4.8.1.3 Chromatography

1.

What is chromatography used to separate?

Chromatography is used to separate and identify substances in a mixture.

2.

What are the stationary phase and mobile phase in paper chromatography?

The stationary phase is the paper and the mobile phase is the solvent.

3.

How does paper chromatography separate substances in a mixture?

Paper chromatography separates substances because they travel at different speeds depending on their solubility and attraction to the paper.

4.

How is the Rf value of a substance calculated?

Rf value = distance travelled by substance ÷ distance travelled by solvent.

5.

A spot moves 6 cm and the solvent moves 12 cm. Calculate the Rf value of the substance.

Rf value = 6 ÷ 12 = 0.5.

6.

How can chromatography be used to distinguish between a pure substance and an impure substance?

Chromatography can distinguish pure and impure substances because a pure substance produces one spot, while an impure substance produces multiple spots.

Required Practical 6: Investigating Paper Chromatography

1.

What is the aim of the required practical investigating paper chromatography?

The aim is to separate and identify substances in a mixture using chromatography.

2.

Why must the solvent level be below the spots on the chromatography paper?

The solvent level must be below the spots so the samples do not dissolve directly into the solvent.

3.

Why is pencil used to draw the baseline in paper chromatography?

Pencil is used because graphite does not dissolve in the solvent.

4.

Why are different solvents used in chromatography experiments?

Different solvents are used because different substances dissolve better in different solvents.

5.

How can Rf values be used to identify unknown substances?

Rf values can be compared with known substances to identify unknown compounds.

6.

Explain why a pure compound produces one spot on a chromatogram.

A pure compound produces one spot because it contains only one substance.

4.8.2.1 Test for Hydrogen

1.

What test is used to identify hydrogen gas?

A lit splint is used to test for hydrogen gas.

2.

What happens when a burning splint is placed into hydrogen gas?

Hydrogen burns with a squeaky pop sound when a burning splint is placed into it.

3.

What sound is produced when hydrogen burns?

A pop sound is produced.

4.

Where is the burning splint placed during the hydrogen test?

The burning splint is placed at the mouth of the container holding the gas.

5.

What observation confirms that a gas is hydrogen?

A squeaky pop confirms the gas is hydrogen.

6.

Explain why hydrogen produces a pop sound during the test.

Hydrogen produces a pop because it reacts quickly with oxygen in the air to form water.

4.8.2.2 Test for Oxygen

1.

What test is used to identify oxygen gas?

A glowing splint is used to identify oxygen gas.

2.

What happens when a glowing splint is inserted into oxygen gas?

The glowing splint relights when placed into oxygen.

3.

What observation confirms that a gas contains oxygen?

Relighting confirms that the gas contains oxygen.

4.

Why does oxygen relight a glowing splint?

Oxygen supports combustion, causing the glowing splint to reignite.

5.

Which type of splint is used to test for oxygen?

A glowing splint is used for the oxygen test.

6.

Explain why oxygen supports combustion.

Oxygen supports combustion because it allows burning reactions to continue.

4.8.2.3 Test for Carbon Dioxide

1.

What solution is used to test for carbon dioxide?

Limewater is used to test for carbon dioxide.

2.

What happens when carbon dioxide is bubbled through limewater?

Carbon dioxide turns limewater cloudy.

3.

What observation confirms that a gas contains carbon dioxide?

Cloudiness confirms the presence of carbon dioxide.

4.

What is the chemical name of limewater?

Limewater is calcium hydroxide solution.

5.

Why does limewater turn cloudy when carbon dioxide is present?

Limewater turns cloudy because calcium carbonate precipitate is formed.

6.

Write the word equation for the reaction between carbon dioxide and calcium hydroxide.

Carbon dioxide + calcium hydroxide → calcium carbonate + water.

4.8.2.4 Test for Chlorine

1.

What test is used to identify chlorine gas?

Damp litmus paper is used to identify chlorine gas.

2.

What happens when damp litmus paper is placed into chlorine gas?

Chlorine bleaches damp litmus paper.

3.

What colour does bleached litmus paper become after reacting with chlorine?

Bleached litmus paper becomes white.

4.

Why must litmus paper be damp when testing for chlorine?

Litmus paper must be damp because chlorine reacts with water to form bleaching substances.

5.

What observation confirms that a gas contains chlorine?

A bleached damp litmus paper confirms chlorine.

6.

Explain why chlorine can be used as a bleaching agent.

Chlorine is used as a bleaching agent because it destroys coloured compounds.

4.8.3.1 Flame Tests

1.

What are flame tests used to identify?

Flame tests are used to identify metal ions.

2.

What flame colour is produced by lithium ions?

Lithium ions produce a crimson flame.

3.

What flame colour is produced by sodium ions?

Sodium ions produce a yellow flame.

4.

What flame colour is produced by potassium ions?

Potassium ions produce a lilac flame.

5.

What flame colour is produced by copper ions?

Copper ions produce a green flame.

6.

A metal compound produces an orange-red flame during a flame test. Identify the metal ion present.

An orange-red flame indicates calcium ions.

4.8.3.2 Metal Hydroxides

1.

Why is sodium hydroxide solution added to solutions containing metal ions?

Sodium hydroxide solution is added to identify metal ions by forming precipitates.

2.

What colour precipitate is formed when copper(II) ions react with sodium hydroxide?

Copper(II) ions produce a blue precipitate.

3.

What colour precipitate is formed when iron(II) ions react with sodium hydroxide?

Iron(II) ions produce a green precipitate.

4.

What colour precipitate is formed when iron(III) ions react with sodium hydroxide?

Iron(III) ions produce a brown precipitate.

5.

Which metal hydroxide precipitate dissolves in excess sodium hydroxide solution?

Aluminium hydroxide dissolves in excess sodium hydroxide solution.

6.

Write the balanced symbol equation for the formation of magnesium hydroxide from magnesium ions and hydroxide ions.

Mg²⁺ + 2OH⁻ → Mg(OH)₂.

4.8.3.3 Carbonates

1.

What gas is produced when carbonates react with dilute acids?

Carbonates react with dilute acids to produce carbon dioxide gas.

2.

How can carbon dioxide produced from a carbonate be identified?

Carbon dioxide is identified using limewater, which turns cloudy.

3.

What happens when carbon dioxide is passed through limewater?

Carbon dioxide turns limewater cloudy because calcium carbonate is produced.

4.

Which type of chemical test can identify carbonate ions?

A chemical test using dilute acid and limewater identifies carbonate ions.

5.

Write the word equation for the reaction between a carbonate and a dilute acid.

Carbonate + acid → salt + water + carbon dioxide.

6.

Explain why carbonate ions can be identified by producing carbon dioxide gas.

Carbonate ions can be identified because they produce carbon dioxide gas.

4.8.3.4 Halides

1.

What solution is used to test for halide ions?

Silver nitrate solution is used to test for halide ions.

2.

Why is dilute nitric acid added before testing for halide ions?

Dilute nitric acid is added to remove interfering ions.

3.

What colour precipitate is formed when chloride ions react with silver nitrate?

Chloride ions produce a white precipitate.

4.

What colour precipitate is formed when bromide ions react with silver nitrate?

Bromide ions produce a cream precipitate.

5.

What colour precipitate is formed when iodide ions react with silver nitrate?

Iodide ions produce a yellow precipitate.

6.

A solution forms a cream precipitate when silver nitrate is added. Identify the halide ion present.

A cream precipitate indicates bromide ions.

4.8.3.5 Sulfates

1.

What solution is used to test for sulfate ions?

Barium chloride solution is used to test for sulfate ions.

2.

Why is dilute hydrochloric acid added when testing for sulfate ions?

Dilute hydrochloric acid is added to remove carbonate ions.

3.

What colour precipitate forms when sulfate ions react with barium chloride?

A white precipitate forms when sulfate ions react with barium chloride.

4.

What observation confirms that sulfate ions are present?

A white precipitate confirms sulfate ions are present.

5.

Write the word equation for the reaction between sulfate ions and barium ions.

Sulfate ions + barium ions → barium sulfate.

6.

Explain why a white precipitate forms when sulfate ions are tested with barium chloride.

A white precipitate forms because insoluble barium sulfate is produced.

Required Practical 7: Identifying Ions in Unknown Ionic Compounds

1.

What is the aim of the required practical identifying ions in unknown compounds?

The aim is to identify unknown ions in an ionic compound.

2.

Which tests can be used to identify metal ions?

Metal ions can be identified using flame tests and sodium hydroxide tests.

3.

Which tests can be used to identify negative ions such as halides and sulfates?

Negative ions can be identified using tests for halides, sulfates and carbonates.

4.

Why are several chemical tests needed to identify an unknown ionic compound?

Several tests are needed because different ions may give similar observations.

5.

How can observations from chemical tests be used to identify unknown ions?

Observations such as colours, precipitates and gases are used to identify ions.

6.

Explain why using more than one test increases confidence when identifying an unknown ionic compound.

Using more than one test increases confidence because results can be confirmed.

4.8.3.6 Instrumental Methods

1.

What are instrumental methods used to identify?

Instrumental methods are used to identify substances and measure their quantities.

2.

Why are instrumental methods useful when only a small amount of chemical is available?

They are useful when only a small sample is available because they are very sensitive.

3.

State three advantages of instrumental methods compared with chemical tests.

Advantages include greater accuracy, faster analysis and use of smaller samples.

4.

Why are instrumental methods used by forensic scientists?

Forensic scientists use instrumental methods to identify unknown substances.

5.

How are instrumental methods different from simple chemical tests?

Instrumental methods use machines and data analysis, while chemical tests rely on observations.

6.

Explain why instrumental methods are considered more accurate than many chemical tests.

Instrumental methods are more accurate because they provide precise measurements.

4.8.3.7 Flame Emission Spectroscopy

1.

What is flame emission spectroscopy used to analyse?

Flame emission spectroscopy is used to analyse metal ions.

2.

How does flame emission spectroscopy identify metal ions?

It identifies metal ions by their unique line spectra.

3.

What type of spectrum is produced in flame emission spectroscopy?

A line spectrum is produced.

4.

How can the concentration of metal ions be measured using flame emission spectroscopy?

Concentration is measured by comparing the intensity of emitted light with reference samples.

5.

Why must a reference set of spectra be used when interpreting flame emission spectroscopy results?

Reference spectra are needed to match unknown samples with known ions.

6.

A sample produces the same line spectrum as a known lithium sample. Explain what this shows about the sample.

A sample with the same spectrum as lithium contains lithium ions.

Topic 8 Review

1.

Explain how melting point and boiling point data can be used to identify pure substances.

Melting point and boiling point data identify pure substances because pure substances have fixed values.

2.

Explain how paper chromatography separates mixtures and identifies substances.

Paper chromatography separates mixtures by differences in solubility and attraction to the stationary phase.

3.

Describe the chemical tests used to identify hydrogen, oxygen, carbon dioxide and chlorine.

Hydrogen gives a squeaky pop, oxygen relights a glowing splint, carbon dioxide turns limewater cloudy and chlorine bleaches damp litmus paper.

4.

Explain how flame tests and precipitation reactions can be used to identify ions.

Flame tests identify metal ions by flame colour and precipitation reactions identify ions by precipitate formation.

5.

Compare instrumental methods with chemical tests for identifying substances.

Instrumental methods are usually faster, more accurate and more sensitive than chemical tests.

6.

Explain how different analytical tests provide evidence about the identity of unknown substances.

Analytical tests provide evidence about unknown substances by comparing observations with known results.

4.9.1.1 The Proportions of Different Gases in the Atmosphere

1.

What percentage of the modern atmosphere is nitrogen?

Nitrogen makes up approximately 78% of the modern atmosphere.

2.

What percentage of the modern atmosphere is oxygen?

Oxygen makes up approximately 21% of the modern atmosphere.

3.

Name two gases found in small proportions in the atmosphere.

Two gases found in small proportions are carbon dioxide and noble gases.

4.

What are the approximate proportions of nitrogen and oxygen in the atmosphere?

The approximate proportions are 78% nitrogen and 21% oxygen.

5.

Why is the composition of the atmosphere described as stable over the last 200 million years?

The composition of the atmosphere is described as stable because the percentages of gases have remained similar for around 200 million years.

6.

What is the most abundant gas in the Earth’s atmosphere?

Nitrogen

4.9.1.2 The Earth’s Early Atmosphere

1.

What gases are thought to have been present in the Earth’s early atmosphere?

The Earth’s early atmosphere is thought to have contained mainly carbon dioxide, water vapour, methane and ammonia.

2.

How did volcanic activity contribute to the formation of the early atmosphere?

Volcanic activity released gases such as carbon dioxide and water vapour, forming the early atmosphere.

3.

Why was there little or no oxygen in the Earth’s early atmosphere?

There was little or no oxygen because photosynthetic organisms had not yet developed.

4.

How did oceans form from water vapour in the early atmosphere?

Oceans formed when water vapour condensed as the Earth cooled.

5.

How did the amount of carbon dioxide in the atmosphere decrease when oceans formed?

Carbon dioxide decreased because it dissolved in oceans and became locked in carbonate rocks.

6.

Explain why evidence about the Earth’s early atmosphere is limited.

Evidence about the early atmosphere is limited because there are few direct records from billions of years ago.

4.9.1.3 How Oxygen Increased

1.

Which process produced the oxygen in the Earth’s atmosphere?

Photosynthesis produced the oxygen in the Earth’s atmosphere.

2.

Which organisms first produced oxygen by photosynthesis?

Algae were the first organisms to produce oxygen by photosynthesis.

3.

Approximately how long ago did algae first produce oxygen?

Algae began producing oxygen approximately 2.7 billion years ago.

4.

How did the increase in oxygen allow animals to evolve?

Increased oxygen allowed animals to evolve because they could use oxygen for aerobic respiration.

5.

Write the word equation for photosynthesis.

Photosynthesis word equation: carbon dioxide + water → glucose + oxygen.

6.

Explain how plants caused the percentage of oxygen in the atmosphere to increase.

Plants increased oxygen levels by removing carbon dioxide and releasing oxygen during photosynthesis.

4.9.1.4 How Carbon Dioxide Decreased

1.

How did plants and algae reduce the amount of carbon dioxide in the atmosphere?

Plants and algae reduced carbon dioxide by absorbing it during photosynthesis.

2.

How were sedimentary rocks formed from carbon dioxide?

Sedimentary rocks formed when carbon dioxide dissolved in oceans and formed carbonate deposits.

3.

How were fossil fuels formed from carbon-containing materials?

Fossil fuels formed from dead organisms containing carbon that were buried and compressed over millions of years.

4.

Why did the formation of limestone reduce carbon dioxide levels?

Limestone formation reduced carbon dioxide by storing carbon in carbonate rocks.

5.

Name three carbon-containing deposits formed over millions of years.

Carbon-containing deposits include fossil fuels, limestone and carbonates.

6.

Explain how photosynthesis and the formation of fossil fuels caused carbon dioxide levels to decrease.

Photosynthesis removed carbon dioxide, while fossil fuel formation stored carbon away from the atmosphere.

4.9.2.1 Greenhouse Gases

1.

What is a greenhouse gas?

A greenhouse gas is a gas that absorbs infrared radiation and contributes to the greenhouse effect.

2.

Name three greenhouse gases.

Three greenhouse gases are carbon dioxide, methane and water vapour.

3.

Why are greenhouse gases important for life on Earth?

Greenhouse gases are important because they keep Earth warm enough for life.

4.

What happens when short wavelength radiation from the Sun reaches Earth?

Short wavelength radiation from the Sun passes through the atmosphere and reaches Earth’s surface.

5.

What happens when long wavelength radiation is emitted from Earth?

Long wavelength radiation emitted from Earth is absorbed and re-emitted by greenhouse gases.

6.

Explain how greenhouse gases cause the greenhouse effect.

Greenhouse gases cause the greenhouse effect by trapping some infrared radiation and warming the atmosphere.

4.9.2.2 Human Activities Which Increase Greenhouse Gases

1.

Name two human activities that increase carbon dioxide levels in the atmosphere.

Burning fossil fuels and deforestation increase carbon dioxide levels.

2.

Name two human activities that increase methane levels in the atmosphere.

Farming and landfill sites increase methane levels.

3.

How does burning fossil fuels increase carbon dioxide levels?

Burning fossil fuels releases carbon dioxide because carbon in fuels reacts with oxygen.

4.

How does farming increase methane levels?

Farming increases methane through livestock digestion and decomposition of waste.

5.

Why do scientists use peer review when studying climate change?

Scientists use peer review to check the reliability and accuracy of climate research.

6.

Explain why evidence about climate change can be difficult to interpret.

Evidence about climate change is difficult to interpret because climate systems are complex and affected by many factors.

4.9.2.3 Global Climate Change

1.

What is global climate change?

Global climate change is the long-term change in average global temperatures and climate patterns.

2.

What is the main cause of the increase in average global temperature?

The main cause of increased global temperature is human activity increasing greenhouse gas levels.

3.

State four possible effects of global climate change.

Effects include rising sea levels, melting ice caps, extreme weather, and changes in ecosystems.

4.

How could rising global temperatures affect sea levels?

Rising temperatures can increase sea levels by melting ice and causing thermal expansion of oceans.

5.

Why is climate change difficult to predict accurately?

Climate change is difficult to predict because many environmental factors interact.

6.

Explain why scientists consider the risks and environmental impacts of global climate change.

Scientists consider risks and impacts to understand possible consequences and develop solutions.

4.9.2.4 The Carbon Footprint and Its Reduction

1.

What is a carbon footprint?

A carbon footprint is the total amount of greenhouse gases released by an activity, product or person.

2.

What greenhouse gases are included when calculating a carbon footprint?

Carbon dioxide and methane are included when calculating carbon footprints.

3.

How can reducing fossil fuel use reduce a carbon footprint?

Reducing fossil fuel use decreases carbon dioxide emissions.

4.

How can reducing methane emissions reduce a carbon footprint?

Reducing methane emissions lowers the carbon footprint by reducing methane release.

5.

Give two actions that can reduce carbon dioxide emissions.

Actions include using renewable energy and improving energy efficiency.

6.

Explain why some methods of reducing carbon footprints are limited.

Some methods are limited because they can be expensive, difficult to implement or have other environmental impacts.

4.9.3.1 Atmospheric Pollutants from Fuels

1.

Which process is a major source of atmospheric pollutants?

Combustion of fuels is a major source of atmospheric pollutants.

2.

What gases can be produced when fuels containing carbon and hydrogen are burned?

Burning fuels containing carbon and hydrogen produces carbon dioxide and water.

3.

How is carbon monoxide produced during combustion?

Carbon monoxide is produced by incomplete combustion.

4.

How are sulfur dioxide and oxides of nitrogen produced during combustion?

Sulfur dioxide is produced when sulfur impurities in fuels burn, and nitrogen oxides form when nitrogen reacts with oxygen at high temperatures.

5.

What are particulates?

Particulates are tiny solid particles released into the atmosphere.

6.

Explain why incomplete combustion can produce carbon monoxide and soot.

Incomplete combustion produces carbon monoxide and soot because there is insufficient oxygen for complete combustion.

4.9.3.2 Properties and Effects of Atmospheric Pollutants

1.

Why is carbon monoxide dangerous to humans?

Carbon monoxide is dangerous because it binds to haemoglobin and prevents oxygen transport in blood.

2.

Why is carbon monoxide difficult to detect?

Carbon monoxide is difficult to detect because it is colourless and odourless.

3.

What problems are caused by sulfur dioxide?

Sulfur dioxide causes acid rain and can irritate the respiratory system.

4.

What problems are caused by oxides of nitrogen?

Oxides of nitrogen contribute to acid rain and respiratory problems.

5.

What problems are caused by particulates in the atmosphere?

Particulates can damage lungs and contribute to global dimming.

6.

Explain how atmospheric pollutants can affect both human health and the environment.

Atmospheric pollutants affect health by causing respiratory problems and affect the environment through acid rain and climate effects.

Topic 9 Review

1.

Describe how the composition of the Earth’s atmosphere has changed over time.

The Earth’s atmosphere changed from mainly carbon dioxide and water vapour to its current composition with high nitrogen and oxygen levels.

2.

Explain how photosynthesis increased oxygen levels and reduced carbon dioxide levels.

Photosynthesis increased oxygen levels by releasing oxygen and reduced carbon dioxide by absorbing it.

3.

Explain how greenhouse gases affect the temperature of the Earth.

Greenhouse gases absorb infrared radiation, trapping heat and warming the Earth.

4.

Describe how human activities contribute to climate change.

Human activities such as burning fossil fuels and farming increase greenhouse gas levels and contribute to climate change.

5.

Explain how combustion of fuels produces atmospheric pollutants.

Combustion produces pollutants such as carbon monoxide, sulfur dioxide, nitrogen oxides and particulates.

6.

Evaluate methods used to reduce greenhouse gas emissions and atmospheric pollution.

Reducing emissions through renewable energy, energy efficiency and pollution controls can reduce greenhouse gas emissions and atmospheric pollution.

4.10.1.1 Using the Earth’s Resources and Sustainable Development

1.

What are natural resources used for by humans?

Natural resources are used by humans to provide materials, fuels, food and energy.

2.

What is meant by a finite resource?

A finite resource is a resource that will run out because it is not replaced quickly enough.

3.

What is meant by a renewable resource?

A renewable resource is a resource that can be replaced naturally.

4.

Give one example of a natural product that can be replaced by an agricultural product.

Natural products can be replaced by agricultural products, for example cotton replacing some animal fibres.

5.

Give one example of a natural product that can be replaced by a synthetic product.

Natural products can be replaced by synthetic products, for example plastics replacing some natural materials.

6.

Explain what is meant by sustainable development.

Sustainable development means meeting the needs of current generations without preventing future generations meeting their needs.

4.10.1.2 Potable Water

1.

What is potable water?

Potable water is water that is safe to drink.

2.

What is the difference between potable water and pure water?

Potable water contains dissolved substances but no harmful microorganisms, while pure water contains only water molecules.

3.

What makes water suitable for drinking as potable water?

Water is suitable as potable water when it has acceptable levels of dissolved substances and is free from harmful microbes.

4.

What are the three main stages used to produce potable water from fresh water?

The three main stages are filtration, sterilisation and testing.

5.

Name three substances or methods that can be used to sterilise water.

Water can be sterilised using chlorine, ozone or ultraviolet light.

6.

Explain why desalination of seawater requires large amounts of energy.

Desalination requires large amounts of energy because separating dissolved salts from seawater requires energy.

Required Practical 8: Analysis and Purification of Water Samples

1.

What properties of water samples are investigated in the required practical analysing water?

Properties investigated include pH, dissolved solids and purity.

2.

How can the amount of dissolved solids in water be measured?

The amount of dissolved solids can be measured by evaporating water and measuring the remaining solid residue.

3.

Why is distillation used when purifying water?

Distillation is used because it removes dissolved substances by evaporating and condensing pure water.

4.

Why is pH measured when analysing water samples?

pH is measured to determine acidity or alkalinity.

5.

Explain why water from different sources may have different levels of dissolved substances.

Water from different sources contains different dissolved minerals and substances.

6.

Explain why distilled water is purer than potable water.

Distilled water is purer than potable water because dissolved substances have been removed.

4.10.1.3 Waste Water Treatment

1.

Why does waste water need to be treated before being released into the environment?

Waste water must be treated to remove harmful substances before release into the environment.

2.

What is removed during the screening and grit removal stage of sewage treatment?

Screening and grit removal remove large solids and particles.

3.

What is produced during the sedimentation stage of sewage treatment?

Sedimentation produces sewage sludge.

4.

What happens during anaerobic digestion of sewage sludge?

Anaerobic digestion breaks down sewage sludge without oxygen and produces methane.

5.

What happens during aerobic biological treatment of effluent?

Aerobic biological treatment uses microorganisms and oxygen to break down organic matter.

6.

Explain why potable water is easier to obtain from fresh water than from waste water or seawater.

Potable water is easier to obtain from fresh water because it contains fewer dissolved substances than seawater or waste water.

4.10.1.4 Alternative Methods of Extracting Metals (HT Only)

1.

Why are alternative methods of metal extraction needed?

Alternative extraction methods are needed because traditional mining can damage the environment and high-grade ores are becoming limited.

2.

What is phytomining?

Phytomining uses plants to extract metals from the ground.

3.

How does phytomining extract metals from the ground?

Plants absorb metal ions from soil, then are harvested and processed to extract the metal.

4.

What is bioleaching?

Bioleaching uses bacteria to produce solutions containing metal compounds.

5.

How can copper be extracted from a solution of copper compounds?

Copper can be extracted from a solution of copper compounds by displacement or electrolysis.

6.

Evaluate one advantage and one disadvantage of using biological methods of metal extraction.

Biological extraction methods have the advantage of being less damaging to the environment but are slower than traditional methods.

4.10.2.1 Life Cycle Assessment

1.

What is a life cycle assessment (LCA)?

A life cycle assessment (LCA) evaluates the environmental impacts of a product throughout its life.

2.

What stages of a product’s life are considered in a life cycle assessment?

It considers raw materials, manufacture, transport, use and disposal.

3.

Why are raw materials considered in a life cycle assessment?

Raw materials are considered because extraction and processing use resources and energy.

4.

Why are pollutant effects harder to include in a life cycle assessment than energy use?

Pollutant effects are harder to include because they are difficult to measure accurately.

5.

Why are selective LCAs sometimes criticised?

Selective LCAs are criticised because they may ignore important environmental impacts.

6.

Explain how a life cycle assessment can be used to compare plastic and paper bags.

An LCA can compare plastic and paper bags by assessing their resource use, energy use and environmental impacts.

4.10.2.2 Ways of Reducing the Use of Resources

1.

What are the three main ways end users can reduce resource use?

The three main ways are reduce, reuse and recycle.

2.

Why does recycling reduce the use of limited resources?

Recycling reduces the use of limited resources by allowing materials to be used again.

3.

Why does recycling metals reduce energy use?

Recycling metals reduces energy use because less energy is needed than extracting new metals from ores.

4.

How can glass bottles be reused or recycled?

Glass bottles can be reused, melted down and recycled into new glass.

5.

How are metals recycled into new products?

Metals are recycled by collecting, sorting, melting and reshaping them into new products.

6.

Explain why recycling reduces environmental impacts caused by mining and quarrying.

Recycling reduces environmental impacts by reducing mining, quarrying and energy consumption.

4.10.3.1 Corrosion and Its Prevention

1.

What is corrosion?

Corrosion is the destruction of metals by reactions with substances in the environment.

2.

What is rusting?

Rusting is the corrosion of iron.

3.

What two substances are needed for iron to rust?

Iron needs oxygen and water to rust.

4.

How can painting prevent iron from rusting?

Painting prevents rusting by creating a barrier that stops oxygen and water reaching the iron.

5.

What is sacrificial protection?

Sacrificial protection uses a more reactive metal to protect iron.

6.

Explain why zinc protects iron from rusting when iron is galvanised.

Zinc protects iron during galvanising because zinc reacts instead of iron and prevents iron from oxidising.

4.10.3.2 Alloys as Useful Materials

1.

What is an alloy?

An alloy is a mixture of a metal with other elements.

2.

What elements are present in bronze?

Bronze contains copper and tin.

3.

What elements are present in brass?

Brass contains copper and zinc.

4.

What is the percentage of gold in 18 carat gold?

18 carat gold contains 75% gold.

5.

Why are alloys often more useful than pure metals?

Alloys are often more useful because they are harder and have improved properties compared with pure metals.

6.

Explain why stainless steel is resistant to corrosion.

Stainless steel resists corrosion because it contains chromium, which forms a protective oxide layer.

4.10.3.3 Ceramics, Polymers and Composites

1.

What materials are used to make soda-lime glass?

Soda-lime glass is made from sand, sodium carbonate and calcium carbonate.

2.

Why does borosilicate glass have a higher melting point than soda-lime glass?

Borosilicate glass has a higher melting point because it contains boron compounds with stronger bonding.

3.

How are clay ceramics produced?

Clay ceramics are produced by shaping clay and heating it at high temperatures.

4.

What is the difference between thermosoftening and thermosetting polymers?

Thermosoftening polymers soften when heated and can be reshaped; thermosetting polymers do not soften because of strong cross-links.

5.

What are the two components of a composite material?

Composite materials contain two or more different materials combined to improve properties.

6.

Explain how the structure of a material affects its properties and uses.

A material’s structure affects its properties, which determines its uses.

4.10.4.1 The Haber Process

1.

What is ammonia used to manufacture?

Ammonia is used to manufacture fertilisers.

2.

What are the raw materials needed for the Haber process?

The raw materials are nitrogen and hydrogen.

3.

What is the source of nitrogen used in the Haber process?

Nitrogen comes from the air.

4.

What is the source of hydrogen used in the Haber process?

Hydrogen comes from natural gas.

5.

What are the conditions needed for Haber process?

Iron catalyst, high temperature (about 450°C) and a high pressure (about 200 atmospheres)

6.

Explain why the Haber process uses high temperature and high pressure.

High temperature and pressure are used as a compromise between reaction rate, yield and cost.

4.10.4.2 Production and Uses of NPK Fertilisers

1.

What elements are present in NPK fertilisers?

NPK fertilisers contain nitrogen, phosphorus and potassium.

2.

Why are NPK fertilisers added to soil?

NPK fertilisers are added to soil to replace nutrients needed for plant growth.

3.

What are the names of the three elements represented by NPK?

N represents nitrogen, P represents phosphorus and K represents potassium.

4.

Why can phosphate rock not be used directly as a fertiliser?

Phosphate rock cannot be used directly because it is insoluble and plants cannot absorb it easily.

5.

Which acids can be used to treat phosphate rock to make fertilisers?

Sulfuric acid, nitric acid or phosphoric acid can be used to treat phosphate rock.

6.

Explain why NPK fertilisers are described as formulations.

NPK fertilisers are formulations because they contain carefully measured amounts of different substances to produce a useful product.

Topic 10 Review

1.

Explain how chemistry helps humans use resources sustainably.

Chemistry helps humans use resources sustainably by developing recycling methods, alternative materials and efficient processes.

2.

Compare the production of potable water from fresh water and seawater.

Potable water from fresh water requires filtration and sterilisation, while seawater requires energy-intensive desalination.

3.

Explain how waste water is treated before being released into the environment.

Waste water is treated by screening, sedimentation, anaerobic digestion and aerobic biological treatment.

4.

Describe methods used to reduce the use of limited resources.

Limited resources can be reduced by reducing use, reusing materials and recycling.

5.

Explain how the properties of alloys, ceramics, polymers and composites make them useful materials.

Alloys, ceramics, polymers and composites have useful properties due to their structures and bonding.

6.

Explain how the Haber process produces ammonia and why the industrial conditions are a compromise.

The Haber process produces ammonia by reacting nitrogen and hydrogen using an iron catalyst at high pressure and temperature; conditions are a compromise between rate, yield and cost.

Chemistry

Paper 1

Topic 1 – Atomic Structure and the Periodic Table