Applying Science to Suggest and Predict Answers

Hello. Last lesson gave you a dependable structure for calculation questions: show the equation, substitution, units, and rounding. This lesson is different: “suggest” and “predict” questions often have no formula and may describe a situation you have not seen before. Your job is not to recall a memorised mark-scheme sentence. It is to select the relevant science you do know and apply it accurately to the new information.

This completes the command-word module. By the end, you should be able to spot the difference between a predicted outcome and a suggested explanation or solution, use details from the question as evidence, and write an answer with enough scientific reasoning for the marks available.

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What Pearson means by “predict” and “suggest”

Use the official International GCSE command-word definitions as your starting point.

The difference is small but important:

Command word	What the examiner wants	Main question to ask yourself
Predict	An expected result when something changes or continues.	“What will happen?”
Suggest	A scientifically plausible cause, explanation, method, or solution in an unfamiliar context.	“What could reasonably explain or solve this?”

A prediction is usually tightly constrained by a scientific relationship, supplied data, or a stated change in conditions. A suggestion has more than one possible correct answer, provided your answer fits the evidence and uses valid science.

For example, if a question says a reaction is carried out with powdered calcium carbonate instead of large chips:

• Predict the effect on rate: “The reaction will be faster.”
• Suggest why the rate is faster: “The powder has a larger surface area, so more collisions occur each second.”

The first answer gives the outcome. The second gives a possible scientific explanation. If the question asks you to “predict and explain,” you need both.

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The thinking routine: clue, science, answer

Unfamiliar questions become manageable when you do not try to solve the whole scenario at once. Instead, work through three small decisions.

1. Find the important clue

Underline or circle what has changed, what the data show, or what problem needs solving.

Typical clues include:

• a change in temperature, concentration, surface area, force, voltage, or light intensity;
• a named apparatus fault, such as a loose bung or heat loss;
• a graph trend;
• an unusual observation, such as yellow leaves or a lower-than-expected yield;
• a practical constraint, such as needing to improve accuracy or reduce risk.

Do not let the story around the question distract you. The mark scheme normally rewards the scientific consequence of one or two key details.

2. Retrieve one relevant rule

Ask: Which topic does this clue connect to?

Examples:

Question clue	Relevant science to retrieve
Smaller solid pieces	Larger surface area; more frequent successful collisions
Lamp moved further from pondweed	Lower light intensity; lower photosynthesis rate if light is limiting
Stomata close	Less water vapour can diffuse out of a leaf
Loose bung in gas apparatus	Gas can escape, so less is collected
Longer wire at the same voltage	Greater resistance; lower current
Metal and wood at the same temperature	Metal transfers thermal energy from the hand more quickly

Usually, one well-chosen principle is better than listing everything you know about the topic.

3. Give the answer at the depth the marks require

For a one-mark question, the outcome or proposal may be enough. For two marks, you will commonly need a statement plus a linked scientific reason.

A useful pattern is:

Answer the question directly. Then add “because” and the relevant scientific mechanism.

For example:

The current will decrease because the longer wire has a greater resistance.

This is concise, precise, and causal. It does not waste time by repeating the entire question.

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Predict: state the expected result, then justify it when needed

A prediction should be specific enough to be checked. Avoid vague answers such as “it will change” or “it will be affected.” State the direction or observable result.

Example 1: Biology prediction

A plant’s stomata close during a hot, dry afternoon.
Predict the effect on the rate of transpiration.

The scientific link is that transpiration involves water vapour leaving through stomata.

A one-mark answer:

The rate of transpiration will decrease.

If the question is worth two marks or says “predict and explain”:

The rate of transpiration will decrease because fewer stomata are open, so less water vapour diffuses out of the leaf.

Notice the difference between simply saying “less water leaves” and explaining how it leaves. “Diffuses out” is stronger scientific vocabulary.

Example 2: Chemistry prediction

A student repeats a reaction using the same mass of a solid reactant, but crushes it into a powder.
Predict the effect on the initial rate of reaction.

The initial rate of reaction will increase.

For an explanation:

The initial rate will increase because the powder has a larger surface area, so more particles can collide successfully each second.

Do not predict that “more product will be made” unless the question gives a reason that the amount of limiting reactant has changed. Crushing changes rate; it does not automatically change the final amount produced.

Example 3: Physics prediction

A wire in a circuit is made longer while the potential difference stays the same.
Predict the effect on the ammeter reading.

The ammeter reading will decrease because the longer wire has a greater resistance.

The expected result is not “the wire will use more electricity.” The ammeter measures current, so answer about current.

When the question includes data or a graph

Data are not decoration. Use them to anchor your prediction.

Suppose a graph shows that increasing light intensity increases photosynthesis rate over the displayed range. If asked to predict the rate at a slightly higher light intensity, a sensible answer is that the rate should increase, perhaps until another factor becomes limiting.

However, be careful with a large extrapolation beyond the data. If a graph shows a trend only from $10$ to $40$ degrees C, you cannot confidently claim it continues unchanged at $100$ degrees C. In Biology especially, enzymes may denature; in other contexts, a relationship may stop being linear.

A careful high-quality prediction can therefore be:

The rate is likely to continue increasing at first, following the trend shown, but it may level off if another factor becomes limiting.

Use this type of qualification only when the evidence genuinely does not support an exact certainty. Do not fill ordinary one-mark questions with unnecessary caveats.

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Suggest: propose a scientifically plausible answer

“Suggest” appears in several forms:

• suggest an explanation;
• suggest why;
• suggest a reason;
• suggest an improvement;
• suggest a method;
• suggest a solution to a problem.

The word after suggest tells you what type of answer is required. Read that phrase carefully.

The following short example from How to answer exam questions 1 by Freesciencelessons reinforces the key idea: several answers may be valid, but they must be scientifically plausible.

“Suggest why”: link the observation to a cause

A student expects to collect $60{\text{ cm}}^3$ of gas, but collects only $42{\text{ cm}}^3$. The diagram shows that the bung is loose.
Suggest why the volume collected is lower than expected.

A strong answer:

Some gas escaped through the loose bung, so it was not collected in the measuring cylinder.

The question gives you the clue: the loose bung. You do not need to invent five unrelated possibilities, such as faulty equipment, wrong temperature, impure chemicals, or poor timing.

“Suggest an explanation”: use the correct mechanism

A metal spoon and a wooden spoon are left in the same room. A student says that the metal spoon feels colder.
Suggest an explanation.

Metal conducts thermal energy away from the student’s hand faster than wood.

Both spoons may be at the same temperature. The difference is the rate of thermal energy transfer, not necessarily the temperature of the objects.

“Suggest an improvement”: state the action and why it helps

A student measures the time taken for a cart to travel a short distance using a hand-held stopwatch.
Suggest an improvement to the method.

A weak answer:

Use better equipment.

A much stronger answer:

Use light gates and a data logger to measure the time, reducing error caused by human reaction time.

The action is specific, and the improvement is linked to the limitation. For a two-mark practical question, that link is often the second marking point.

“Suggest a solution”: satisfy the problem’s constraints

A farmer wants to reduce water loss from plants during a dry period.
Suggest one action the farmer could take.

The farmer could use a greenhouse or covering to reduce air movement around the leaves.

If asked to explain:

This reduces evaporation and maintains a more humid environment, reducing transpiration.

Do not offer a solution that creates a new problem. For example, “increase temperature” would generally increase water loss, not reduce it.

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Use the mark allocation to decide how much to write

You already know from earlier lessons that marks are a clue to the number and depth of marking points. This matters especially here.

Question style	Likely answer structure
Predict $[1]$	One precise expected result
Suggest one reason $[1]$	One plausible cause or idea
Predict and explain $[2]$	Predicted result plus scientific mechanism
Suggest an explanation $[2]$	Possible cause plus how it produces the observation
Suggest an improvement $[2]$	Specific action plus why it improves data quality, safety, or control
Suggest two reasons $[2]$	Two distinct reasons, not the same idea repeated differently

A long answer is not automatically a better answer. If a one-mark question asks you to predict the ammeter reading, write “decreases,” not a full paragraph about electrical circuits.

On the other hand, a two-mark “suggest why” response that only says “gas escaped” may be incomplete. Add the consequence: “so less gas was collected.”

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Common traps and how to avoid them

Treating “suggest” as guessing

A suggestion may be one of several valid answers, but it must still use correct science and fit the information provided.

Instead of:

Maybe something went wrong.

Write:

The reactant may not have fully dissolved, so fewer particles were available to react.

The second answer identifies a possible issue and gives a scientific consequence.

Giving a cause when the question asks for a prediction

If the question says “predict the effect on mass,” answer about mass first.

Weak:

There are more collisions.

Better:

The mass decreases more quickly because the reaction is faster and gas escapes from the flask.

The predicted observation comes first; the reasoning follows.

Repeating the wording of the question

Weak:

The rate increases because the reaction is faster.

This is circular: “faster” does not explain why it is faster.

Better:

The rate increases because increasing temperature gives particles more kinetic energy, so more collisions have enough energy to react.

Ignoring a limiting factor

Science often depends on conditions. A prediction needs the relevant condition stated where necessary.

For example:

Increasing light intensity increases photosynthesis rate while light is the limiting factor.

If the rate has already levelled off, light intensity may no longer be the factor controlling the rate.

Offering several conflicting answers

Do not write a list of possibilities in the hope that one is correct:

It could be heat loss, a loose bung, impurities, inaccurate equipment, or a different concentration.

This looks like guessing and can include contradictions. Choose the explanation best supported by the question’s information. If the question explicitly asks for two reasons, give two distinct, relevant reasons.

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A quick method for unfamiliar past-paper questions

When you meet a “suggest” or “predict” question in a past paper, annotate it before writing:

1. Box the command word: predict or suggest.
2. Underline the target: what exactly must you predict, explain, improve, or solve?
3. Circle the clue: the changed variable, observation, data trend, or apparatus issue.
4. Write one topic keyword in the margin: collisions, diffusion, resistance, natural selection, energy transfer, and so on.
5. Build the answer using result or proposal, then a scientific “because” link if the marks require it.

When marking, do not only record that the answer was wrong. Classify the cause:

• SP1 — target missed: answered about the wrong variable or observation.
• SP2 — vague prediction: said “changes” rather than increase, decrease, or a clear outcome.
• SP3 — unsupported suggestion: offered an idea not linked to the question’s evidence.
• SP4 — missing mechanism: gave an outcome or cause but no scientific link for available marks.
• SP5 — wrong topic rule: applied the wrong principle, such as confusing rate with final yield.
• SP6 — imprecise vocabulary: knew the idea but missed essential wording such as diffusion, resistance, or successful collisions.

Turn recurring errors into flashcards. Good examples include:

Flashcard front	Flashcard back
What does “predict” require?	An expected result based on the information and known science. State the outcome clearly.
What does “suggest” require?	A scientifically plausible cause, explanation, method, or solution applied to a novel context.
What is the usual two-mark structure?	Direct answer, then a linked scientific reason or mechanism.
How do I avoid guessing in a suggest question?	Use the clue in the question and one relevant scientific principle.
What should I check before submitting a prediction?	Have I stated the variable or observable result the question actually asks about?

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Key takeaways

• Predict means state an expected result; be precise about what increases, decreases, changes, or happens.
• Suggest means apply valid science to an unfamiliar problem, observation, or situation. More than one answer can be correct, but it must fit the evidence.
• Use the routine: identify the clue, retrieve one relevant scientific rule, then answer at the depth the marks require.
• For two-mark questions, a strong default is: direct answer + because + scientific mechanism.
• Avoid vague claims, circular explanations, lists of random possibilities, and answers about the wrong variable.
• In past-paper review, log whether an error came from missing the target, choosing the wrong science, or failing to express the mechanism.

You have now completed the command-word foundations. The next module begins Biology content with classification: recognising the defining features of plants, animals, fungi, protoctists, bacteria, and viruses.