Most GCSE Science marks are not lost because students do not know the content. They are lost in the way students answer questions. The same mistakes appear on marked papers year after year, across every exam board, at every grade level. The students who fix these habits before sitting their papers are the ones who consistently outperform where their knowledge alone would have placed them.
Below are the four mistakes we see most often, what to do instead, and a full command word guide with real exam questions and model answers so you can see exactly what a full mark response looks like.
Mistake 1: Explaining when the question only asks you to describe
This is one of the most common and most costly habits in GCSE Science. A student reads a question, knows the topic well, and writes everything they understand about it, including the reasons why something happens. The problem is the question asked them to describe, not explain. Those are two different instructions with two different mark schemes.
When a question says describe, the examiner wants to know what happens. What changes, what increases, what decreases, what the trend shows. Adding the reason why it happens wastes time and can introduce errors that lose marks already earned. Students who over-answer describe questions often run short on time later in the paper where the marks are higher.
If the question says describe, stop at what happens. If it says explain, give the reason. If it says describe and explain, do both in that order. Reading the command word before anything else is the first habit every Science student needs to build.
Mistake 2: Not using the data provided
If a question includes a graph, a table, a figure or any numerical data, that information is there for a reason. The examiner expects you to use it. Students who write general answers without referencing the data leave marks on the table, even when their scientific understanding is completely correct.
The approach that consistently picks up full marks on data questions follows a clear sequence. First, describe the general trend. Second, quote specific figures from the data to support that trend. Third, identify any point where the trend changes or levels off and state the value at which that happens. If the question also asks you to explain, add the scientific reason only after doing all of that.
For example, if a graph shows the relationship between the distance of a lamp from pondweed and the rate of photosynthesis, a full answer would state: as the distance of the lamp decreases, the rate of photosynthesis increases. The rate continues to increase until the lamp is 5 cm from the pondweed, at which point the graph levels off and there is no further increase. If the question then asks why the graph levels off, the explanation is that light is no longer the limiting factor at that distance, so increasing light intensity has no further effect.
An answer that says "the rate increases then levels off" will score fewer marks than one that says "the rate increases from 2 bubbles per minute to 14 bubbles per minute, then levels off at 5 cm." The figures are in front of you. Use them.
Mistake 3: Ignoring the number of marks
The mark allocation for every question is printed on the paper. It is not decoration. It tells you exactly how many distinct points the examiner expects to see in your answer.
A one-mark question needs one clear point. A four-mark question needs four developed points, or two well-explained points where each earns two marks through development. Students who write a single sentence in response to a four-mark question will not score four marks regardless of how accurate that sentence is.
Before writing anything, look at the mark allocation. Count how many points you need to make, then write your answer with that number in mind and check before moving on. This habit alone can recover several marks across a paper.
One-mark questions are short. Four-mark questions require development. Six-mark questions are extended responses where structure and scientific logic matter as much as the content itself. Match your answer length to the marks available and you will not leave points behind.
Mistake 4: Writing everything you know
This is the flip side of mistake three and it is just as damaging. Some students, particularly those who have revised thoroughly, respond to questions by writing everything they know about the topic. It feels thorough. In practice it rarely helps and can actively hurt.
Examiners only award marks for relevant points. Irrelevant content does not score, and in longer questions it can contradict a correct point and cost you the mark already earned. It also wastes time that should be spent on other questions.
Read the question carefully before writing anything. Identify exactly what is being asked, then answer only that. If the question asks about the effect of temperature on enzyme activity, it does not want the full story of enzyme structure, lock and key theory and denaturation unless it specifically asks for an explanation of why the effect occurs. Stay focused and write only what earns marks.
"More words is not more marks. Relevant words are marks. Students who learn the difference between those two things consistently outperform students who simply know more."
The command word guide with model answers
Every question in a GCSE Science paper opens with a command word. That word tells you exactly what the examiner wants. Misreading it is the single most avoidable source of mark loss in Science exams. Below is every command word you will encounter, what it means, and a real exam question with a model answer showing exactly what full marks looks like.
Describe
Say what happens. Give observations or trends only. Do not give reasons.
Example question: A student investigated the effect of exercise on heart rate. Their results are shown in a table with heart rate recorded at 0, 2, 4, 6 and 8 minutes. Describe the change in heart rate during the investigation. (3 marks)
Model answer: The heart rate increased from 72 bpm to 142 bpm between 0 and 6 minutes. It increased rapidly at first and then more slowly. After 6 minutes, the heart rate decreased to 120 bpm.
This scores well because it gives the trend, uses the data, and does not attempt to explain why the heart rate changes.
Explain
Give reasons using scientific knowledge. Link cause to effect.
Example question: Explain why heart rate increases during exercise. (4 marks)
Model answer: During exercise, muscles respire more rapidly and require more oxygen and glucose. The heart pumps faster to deliver these substances to the muscles. Increased blood flow also removes more carbon dioxide produced by respiration.
This scores well because it links cause to effect, uses scientific vocabulary, and explains the biology behind the observation rather than simply describing it.
Compare
Give both similarities and differences. You must address both to score full marks.
Example question: Compare plant cells and animal cells. (4 marks)
Model answer: Both plant and animal cells contain a nucleus, cytoplasm and a cell membrane. Plant cells also contain chloroplasts and a permanent vacuole, which animal cells do not have. Plant cells have a cell wall, whereas animal cells do not.
This scores well because it covers both similarities and differences and uses comparative language such as "whereas" to make the contrast explicit.
Evaluate
Give advantages, disadvantages and a final judgement. All three are expected.
Example question: A farmer uses pesticides to increase crop yield. Evaluate the use of pesticides in farming. (6 marks)
Model answer: Pesticides can increase crop yield by killing pests that damage plants. This can increase profits and food production. However, pesticides may harm non-target organisms such as bees and can enter food chains. Some pests may also develop resistance over time. Overall, pesticides can be useful for increasing food production, but they should be used carefully to reduce environmental damage.
This scores well because it gives clear pros, clear cons and ends with a balanced conclusion. A 6-mark evaluate question with no conclusion will not reach full marks.
Suggest
Apply your scientific knowledge to an unfamiliar situation. There may not be one single correct answer, but your reasoning must be scientifically sound.
Example question: Fish in a pond are dying after fertiliser washed into the water. Suggest why the fish died. (3 marks)
Model answer: The fertiliser may have caused algae to grow rapidly. When the algae died, decomposers respired and used up oxygen in the water. The oxygen levels became too low for the fish to survive.
This scores well because it uses logical scientific reasoning and applies known biological ideas to an unfamiliar scenario.
Calculate
Show all working. A correct final answer with no working shown can score zero if the method cannot be seen.
Example question: A student counted 48 plants in a 12 m² area. Calculate the population density in plants per m². (2 marks)
Model answer: 48 divided by 12 = 4 plants per m²
This scores well because the formula is applied, the substitution is shown and the correct units are included. Never skip steps in a calculate question even when the arithmetic feels simple.
State / Give / Name
A short factual answer only. One or two words is often enough. Do not over-explain.
Example question: Name the part of the cell that controls cell activities. (1 mark)
Model answer: Nucleus.
This scores well because it is simple, direct and does not add unnecessary information. Adding an explanation to a State or Name question wastes time and gains no marks.
Discuss
Consider multiple viewpoints or factors. Show that you have thought about the topic from more than one angle.
Example question: Discuss whether genetic engineering should be used in agriculture. (6 marks)
Model answer: Genetic engineering can increase crop yields and produce plants resistant to disease or drought. This could reduce food shortages, and some genetically modified crops may also reduce the need for pesticides. However, some people are concerned about possible environmental effects such as reduced biodiversity. Others worry about unknown long-term health effects or ethical issues. Overall, genetic engineering has important benefits, but careful regulation and testing are necessary.
This scores well because it presents multiple perspectives, covers both scientific and ethical considerations and reaches a balanced conclusion.
Identify
Pick out specific information directly from the data or diagram provided. Do not add explanation.
Example question: A graph shows enzyme activity at different temperatures. Identify the temperature at which enzyme activity is highest. (1 mark)
Model answer: 40°C.
This scores well because it directly selects the correct information without adding unnecessary commentary. The answer is in front of you in the graph. Read it and write it down.
Determine
Work something out from the information given. Show how you reached your answer.
Example question: A student measured pulse rate before exercise as 68 bpm and after exercise as 104 bpm. Determine the increase in pulse rate. (2 marks)
Model answer: 104 minus 68 = 36. Increase in pulse rate = 36 bpm.
This scores well because the method is shown and the final answer is clearly stated with the correct unit.
Plan
Design an investigation. Include the independent variable, dependent variable, control variables and how you would ensure results are valid and reliable.
Example question: Plan an investigation to test the effect of light intensity on the rate of photosynthesis in pondweed. (6 marks)
Model answer: Place a piece of pondweed in water containing sodium hydrogencarbonate solution. Position a lamp at different distances from the pondweed to change light intensity. Measure the rate of photosynthesis by counting the number of oxygen bubbles produced per minute. Repeat each distance three times and calculate a mean. Keep temperature, type of pondweed and time interval the same throughout the investigation.
This scores well because it clearly identifies the independent variable (light intensity), dependent variable (bubble count) and control variables, and mentions repeats to ensure reliability.
Most students read the full question and then decide how to answer it. The better habit is to read the command word first, so you know what kind of answer is expected before taking in any of the detail. It takes one second and changes the way you process everything that follows.
Putting it together
These four mistakes and the command word guide above are not complicated ideas. The difficulty is applying them consistently under exam pressure, when the temptation is to write quickly and move on. The students who perform best in GCSE Science are usually not the ones who know the most. They are the ones who have practised answering questions the right way often enough that it becomes automatic.
Before each answer: read the command word, check the mark allocation, identify what data has been provided. Then write a focused, structured response that addresses exactly what has been asked. That process repeated across every question on every paper is what separates a grade 6 from a grade 8 in Science far more often than content knowledge alone.
If you are working through past papers and finding that your marks are lower than your knowledge suggests they should be, exam technique is almost certainly the gap. It is also the quickest thing to fix.
