Primary 5 Science Learning Guide | Explain, Compare, Predict & Evaluate Questions

A Science answer can contain correct facts and still miss the question. The command tells you what job those facts must perform.

Wait, What? “I Knew the Science” Does Not Always Mean “I Answered the Question”

Primary 5 Science begins to demand answer control. A student may know that evaporation occurs faster under certain conditions, that the heart pumps blood, that pollination transfers pollen or that a circuit must be complete. Yet marks can still be lost because an explain question receives a description, a compare question discusses only one setup, or an evidence question receives a memorised mechanism instead of data from the experiment.

The solution is not to write longer answers. It is to match the response to the job.

Quick Answer

State gives the required fact directly. Describe reports what is observed, measured or shown. Explain connects a condition to a scientific mechanism and outcome. Compare uses the same scientific basis to show a relevant similarity or difference between two cases. Predict applies a known relationship to a changed condition. Evaluate judges the strength, limitation or suitability of a method, conclusion or model using evidence.

The Command-Word Map

Command	Main job	Common failure
State / Identify	Give the required fact, part, variable or result	Adds unrelated explanation
Describe	Say what the observation, table, graph or process shows	Explains why instead of reporting what happened
Explain	Connect condition → mechanism → outcome	Names a keyword but leaves out the causal link
Compare	Use one scientific basis across both cases	Describes only one case
Predict	Apply a relationship to a new condition	Guesses without mechanism
Evaluate	Judge using evidence, controls, limits or suitability	Uses vague praise such as “good” or “fair”

State: Stop When the Job Is Complete

If the question asks, “State the process by which liquid water changes into water vapour from the surface,” the answer is evaporation. A long explanation is unnecessary unless requested. Extra writing can waste time or introduce errors.

Answer control includes knowing when to stop.

Describe: Use What the Evidence Shows

A description should stay close to the data or observation. Suppose a graph shows pulse rate decreasing from 128 to 82 beats per minute during six minutes of recovery.

Good description: “Pulse rate decreased as recovery time increased.”

Not yet a description: “The heart slowed because the muscles needed less oxygen.” That may be an explanation, but it answers a different job.

Explain: Build the Missing Middle

A reliable explanation frame is:

• Condition: what is different?
• Mechanism: what process or function changes?
• Outcome: what result follows?

Where the question provides data, bind the explanation to the evidence as well.

Worked Explain 1: Evaporation

Two equal masses of water are left for one hour. Dish A has a larger exposed surface area and loses more mass.

Weak: “Dish A has more evaporation.”

Better: “Dish A has a larger exposed surface area, so evaporation can occur from a larger surface. More water therefore changes into water vapour in the same time, causing a larger decrease in mass.”

Worked Explain 2: Exercise

Question: Explain why breathing rate increases during exercise.

Better answer: “During exercise, body cells require oxygen at a faster rate and produce carbon dioxide at a faster rate. Breathing rate increases so more oxygen can enter the lungs and more carbon dioxide can be removed.”

If the question asks about pulse instead, the mechanism must shift to blood transport and heart pumping. Similar context does not mean identical answer.

Compare: Use the Same Basis

A comparison is strongest when both cases are discussed using the same scientific property. “Flower A is brightly coloured while Flower B has exposed anthers” is not a clean comparison because the two statements use different features. A better answer might compare the position of reproductive structures, amount of pollen or likely pollination mechanism using parallel language.

The Comparison Frame

• Basis: which property or process are you comparing?
• Case A: what is true under that basis?
• Case B: what is true under the same basis?
• Relationship: similar, greater, lower, faster, slower, present, absent or different route?

Worked Compare 3: Inhaled and Exhaled Air

Good comparison: “Exhaled air contains less oxygen and more carbon dioxide than inhaled air.”

The same two gases are compared across both air samples. Avoid saying “exhaled air has carbon dioxide but inhaled air has oxygen,” because both gases can be present in both samples.

Worked Compare 4: Two Circuits

Circuit A has two bulbs in one series path. Circuit B places two bulbs on separate branches.

Comparison: “Circuit A has only one conducting path through both bulbs, whereas Circuit B has separate branches that provide more than one path.”

This comparison focuses on connection architecture rather than appearance.

Predict: Apply the Relationship, Do Not Guess

A prediction should use an established relationship and the new condition. The strongest predictions often follow the same condition → mechanism → outcome chain as explanations.

Worked Predict 5: Air Movement

A wet cloth is moved from still air into stronger moving air while other important conditions remain similar.

Prediction: “The cloth will dry faster because moving air carries water vapour away from the wet surface more quickly, allowing evaporation to continue at a higher rate.”

Worked Predict 6: Broken Circuit Branch

Two lamps are on separate complete branches. The wire in Branch A is cut.

Prediction: “Lamp A will go out because its branch is open. Lamp B can remain lit if its own branch still forms a complete circuit through the source.”

Evaluate: Name the Criterion

Evaluation answers become vague when students write “the experiment is not fair” without explaining why. A stronger answer names the criterion: reliability, accuracy, validity, control, sample size, measurement suitability or model limitation.

Worked Evaluate 7: Pollination Experiment

A student tests whether insects affect fruit formation by covering one flower with a plastic bag and leaving one flower uncovered.

Problem 1 — sample size: one flower in each condition is vulnerable to natural biological variation.

Problem 2 — validity: a plastic bag may change temperature, humidity and airflow as well as insect access.

Improvement: use several similar flowers in each group and a covering that blocks the intended pollinator while reducing unintended environmental differences.

Evidence Questions: “How Do You Know?”

“How do you know?” usually asks for the observation or data that supports a claim. It is not always asking “why does this happen?”

Question: How do you know that water moved upward through the stem?

Evidence answer: “Coloured water appeared in transport pathways higher in the stem and later in the flower.”

Mechanism answer: “Water-carrying tubes transport water upward.” This may be scientifically correct, but it does not provide the requested evidence.

Two-Command Questions

Some questions contain two jobs: “Compare the results and explain the difference.” Completing only one half loses marks even if that half is excellent.

1. Underline or mentally isolate each command.
2. Complete the first job.
3. Complete the second job.
4. Check that the explanation uses the comparison just stated.

Worked Two-Command 8: Water Loss

Plant A has greater leaf area than Plant B. After two hours, Plant A’s container loses 18 g of water while Plant B’s loses 7 g.

Compare: “Plant A’s container lost more water than Plant B’s container over the same two hours.”

Explain: “Plant A had greater leaf area, so more water could be lost through its leaves. More water was therefore drawn from the container through the plant, causing the larger decrease.”

Answer Length: Enough Science, Not Maximum Science

Longer answers are not automatically safer. Every extra sentence creates another chance to contradict the question, introduce a wrong fact or answer a different job. A good Primary 5 response contains the required scientific relationship and the relevant evidence, then stops.

The Three-Layer Explanation

Layer	Purpose	Example
Condition	Anchor to the setup	Dish A has larger exposed surface area
Mechanism	State the scientific process	Evaporation occurs from a larger surface
Outcome	Connect to observation	More water is lost in the same time

Not every question needs exactly three sentences, but every explanation should contain the necessary logic.

Answer Precision in Reproduction

Weak: “The insect helps the plant reproduce.”

Better: “The insect can transfer pollen from an anther to a stigma. This pollination allows the male reproductive cell to be delivered toward an ovule, where fertilisation may occur.”

The stronger answer identifies the exact reproductive job instead of using a broad outcome word.

Answer Precision in Circulation

Weak: “The heart gives muscles oxygen.”

Better: “The heart pumps blood through the circulatory system. The blood transports oxygen from the lungs to body cells, including working muscle cells.”

Answer Precision in Electricity

Weak: “The switch is off.”

Better: “The switch is open, so the conducting path is broken and the circuit is incomplete. The bulb therefore does not light.”

Do Not Invent Missing Conditions

If the question says Dish A has a larger surface area, do not explain the result using “higher temperature” unless the setup also provides that condition. Science answers should be constrained by the evidence and information given. A plausible cause is not automatically the tested cause.

Conditional Language

Scientific claims sometimes need words such as may, can, supports, under these conditions or is consistent with. These do not make an answer weak. They make the level of certainty match the evidence.

For example, one observation of an insect visiting a flower does not prove it is the only pollinator. The evidence may support the possibility that the insect helps transfer pollen.

Evaluate a Conclusion, Not Just the Method

A conclusion can overreach even when the data are correct. Suppose a student tests one metal and one plastic and concludes, “All metals conduct and all plastics insulate.” The experiment may support statements about the tested samples, but it is too small to establish a universal claim about every material in those broad classes.

Question Checking Routine

1. What is the command?
2. What scientific topic or relationship is relevant?
3. What evidence or condition from the question must appear in the answer?
4. Does the response perform the exact job?
5. Is any sentence unsupported or unnecessary?
6. If there are two commands, did both get answered?

Worked Answer Surgery: Four Versions

Question: Two similar bulbs are connected differently. Bulb A is brighter. Explain why.

Too vague: “Because Circuit A is better.”

Topic keyword only: “Because of electricity.”

Invented detail: “Because Cell A is newer,” when the question does not say that.

Controlled answer: Use the exact circuit difference shown—such as number of cells, number of bulbs or arrangement—and connect that condition to the observed brightness without introducing unsupported factors.

Common Command-Word Traps

• Explain answered with “because” but no mechanism. The word does not create causality by itself.
• Compare answered with two unrelated descriptions. Use the same scientific basis.
• Predict answered with a guess. Apply a known relationship.
• Evidence question answered with textbook knowledge. Use the observation or measurement supplied.
• Evaluate answered with “not fair”. Name the design problem and its consequence.
• State question answered with an essay. Stop after the required fact.
• Two-command question answered halfway. Count the jobs before writing.

Model Limit: Command Words Depend on Context

No single template can replace reading the whole question. “Explain” may require one link in a simple item and several links in a systems question. “Compare” may ask for one difference or several similarities and differences. “Evaluate” may focus on method, evidence, conclusion or model. The command-word map is a control system, not a script to copy blindly.

Unfamiliar Transfer Test

Take one unfamiliar P5 diagram or data set and write six different questions about it: state, describe, explain, compare, predict and evaluate. Then answer each in a different form. This exercise teaches that the same scientific information can support different response jobs.

Delayed Return Test

Several days later, take four previous errors and cover the model answers. Identify the command word first. Write only the minimum complete response. Compare with the original marking and ask whether the previous error was concept, evidence, command, mechanism or precision.

Primary 5 Answer-Control Receipt

• I can distinguish state, describe, explain, compare, predict and evaluate.
• I use evidence when asked “How do you know?”
• I build explanations with condition, mechanism and outcome.
• I compare both cases using the same scientific basis.
• I predict from a known relationship rather than guessing.
• I evaluate a specific feature of method, evidence or conclusion.
• I do not invent conditions that are not in the question.
• I use conditional language when the evidence does not justify certainty.
• I answer every command in a multi-part question.
• I stop when the scientific job is complete.

Parent and Tutor Teaching Guide

When marking practice, label the error before correcting the content. Was the science wrong, or did the student answer the wrong command? If the child knows the concept but repeatedly misreads command words, more chapter notes will not solve the problem. Practise one dataset with several different command words so the response job becomes visible.

Ask children to justify every extra sentence. If it does not answer the command, use evidence or complete the mechanism, remove it. Precision is not minimalism for its own sake; it is disciplined alignment between question and response.

Official Reference Route

Singapore Ministry of Education — Primary Science Teaching & Learning Syllabus 2023

This is an independent eduKate Sengkang learning guide. Follow current official syllabus documents and school assessment instructions for formal requirements.

Continue the Primary 5 Science System

• Primary 5 Science Learning Hub
• Variables, Fair Tests & Experimental Design
• Diagrams, Tables, Graphs & Evidence
• Structure, Function, Systems & Cause-and-Effect

The Quiet Return

Strong Science answers are not built by pouring everything remembered onto the page. Read the command. Find the evidence. Select the scientific relationship. Complete the required reasoning and stop. That control is what allows knowledge to survive unfamiliar questions.