PSLE Learner’s Guide · Volume 1035
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During evaporation of salt solution under ordinary classroom conditions, water leaves the surface as water vapour while the dissolved salt does not evaporate with it and becomes more concentrated in the remaining liquid.
Series routes: Use the complete PSLE Learner’s Guide volume directory, the original PSLE Learning Guide and the Science learning hub.
This guide uses original Primary 6 practice and does not predict a live question. Consult the SEAB PSLE formats examined in 2026 page for official information.
Open the full chapter index
- 1. Name solute and solvent
- 2. Trace the evaporating component
- 3. Keep the salt in the container
- 4. Explain increasing concentration
- 5. Place crystal formation correctly
- 6. Separate evaporation from filtration
- 7. Control recovery claims
- 8. Audit the component paths
- 9. Worked examples
- 10. Independent practice
- 11. Delayed transfer
- 12. Family guidance and FAQs
CHAPTER 1 OF 12 · Back to contents
1. Name solute and solvent
In salt solution, salt is the dissolved solute and water is the solvent. The mixture appears uniform, but the two components can follow different paths during separation.
Build the explanation by naming the salt solution container temperature exposed surface desired product and safety boundary and the escape of water particles into the air while non-volatile salt particles remain in the solution. A remembered keyword is not enough: connect the observation to the mechanism and identify what would have to change for the conclusion to change.
Repair the nearest misconception by checking whether an observation shows concentration crystal formation complete dryness or recovery of a separate component and returning to solution solute solvent salt water evaporation vapour concentration saturated crystal residue dissolved particle surface heating boiling condensation distillation mass boundary apparatus safety observation mechanism and conclusion. State why the tempting alternative is too strong, incomplete or about a different stage.
- Check the salt solution container temperature exposed surface desired product and safety boundary.
- Check the escape of water particles into the air while non-volatile salt particles remain in the solution.
- Check whether an observation shows concentration crystal formation complete dryness or recovery of a separate component.
- Check solution solute solvent salt water evaporation vapour concentration saturated crystal residue dissolved particle surface heating boiling condensation distillation mass boundary apparatus safety observation mechanism and conclusion.
CHAPTER 2 OF 12 · Back to contents
2. Trace the evaporating component
Water particles at the surface can gain enough energy to leave the liquid and enter the air as water vapour. Evaporation can occur below the boiling point and happens at the surface.
Build the explanation by naming the salt solution container temperature exposed surface desired product and safety boundary and the escape of water particles into the air while non-volatile salt particles remain in the solution. A remembered keyword is not enough: connect the observation to the mechanism and identify what would have to change for the conclusion to change.
Repair the nearest misconception by checking whether an observation shows concentration crystal formation complete dryness or recovery of a separate component and returning to solution solute solvent salt water evaporation vapour concentration saturated crystal residue dissolved particle surface heating boiling condensation distillation mass boundary apparatus safety observation mechanism and conclusion. State why the tempting alternative is too strong, incomplete or about a different stage.
CHAPTER 3 OF 12 · Back to contents
3. Keep the salt in the container
Ordinary dissolved salt is non-volatile under these conditions, so it does not leave with the water vapour. As water is lost, the same salt is present in less liquid.
Build the explanation by naming the salt solution container temperature exposed surface desired product and safety boundary and the escape of water particles into the air while non-volatile salt particles remain in the solution. A remembered keyword is not enough: connect the observation to the mechanism and identify what would have to change for the conclusion to change.
Repair the nearest misconception by checking whether an observation shows concentration crystal formation complete dryness or recovery of a separate component and returning to solution solute solvent salt water evaporation vapour concentration saturated crystal residue dissolved particle surface heating boiling condensation distillation mass boundary apparatus safety observation mechanism and conclusion. State why the tempting alternative is too strong, incomplete or about a different stage.
CHAPTER 4 OF 12 · Back to contents
4. Explain increasing concentration
Before crystals form, removing water raises the amount of salt per unit volume of remaining solution. A smaller liquid volume does not mean the salt has vanished.
Build the explanation by naming the salt solution container temperature exposed surface desired product and safety boundary and the escape of water particles into the air while non-volatile salt particles remain in the solution. A remembered keyword is not enough: connect the observation to the mechanism and identify what would have to change for the conclusion to change.
Repair the nearest misconception by checking whether an observation shows concentration crystal formation complete dryness or recovery of a separate component and returning to solution solute solvent salt water evaporation vapour concentration saturated crystal residue dissolved particle surface heating boiling condensation distillation mass boundary apparatus safety observation mechanism and conclusion. State why the tempting alternative is too strong, incomplete or about a different stage.
CHAPTER 5 OF 12 · Back to contents
5. Place crystal formation correctly
When the remaining solution becomes sufficiently concentrated and conditions allow, excess dissolved salt can form solid crystals. Crystal formation is evidence of salt recovery, not salt changing into water.
Build the explanation by naming the salt solution container temperature exposed surface desired product and safety boundary and the escape of water particles into the air while non-volatile salt particles remain in the solution. A remembered keyword is not enough: connect the observation to the mechanism and identify what would have to change for the conclusion to change.
Repair the nearest misconception by checking whether an observation shows concentration crystal formation complete dryness or recovery of a separate component and returning to solution solute solvent salt water evaporation vapour concentration saturated crystal residue dissolved particle surface heating boiling condensation distillation mass boundary apparatus safety observation mechanism and conclusion. State why the tempting alternative is too strong, incomplete or about a different stage.
CHAPTER 6 OF 12 · Back to contents
6. Separate evaporation from filtration
Filter paper cannot normally remove dissolved salt from salt solution. Evaporation removes solvent from the mixture, while filtration removes suitable insoluble particles.
Build the explanation by naming the salt solution container temperature exposed surface desired product and safety boundary and the escape of water particles into the air while non-volatile salt particles remain in the solution. A remembered keyword is not enough: connect the observation to the mechanism and identify what would have to change for the conclusion to change.
Repair the nearest misconception by checking whether an observation shows concentration crystal formation complete dryness or recovery of a separate component and returning to solution solute solvent salt water evaporation vapour concentration saturated crystal residue dissolved particle surface heating boiling condensation distillation mass boundary apparatus safety observation mechanism and conclusion. State why the tempting alternative is too strong, incomplete or about a different stage.
CHAPTER 7 OF 12 · Back to contents
7. Control recovery claims
Simple evaporation can recover salt, but collecting the water separately requires condensation of vapour in a suitable distillation arrangement. Water vapour released into the room is not already collected liquid water.
Build the explanation by naming the salt solution container temperature exposed surface desired product and safety boundary and the escape of water particles into the air while non-volatile salt particles remain in the solution. A remembered keyword is not enough: connect the observation to the mechanism and identify what would have to change for the conclusion to change.
Repair the nearest misconception by checking whether an observation shows concentration crystal formation complete dryness or recovery of a separate component and returning to solution solute solvent salt water evaporation vapour concentration saturated crystal residue dissolved particle surface heating boiling condensation distillation mass boundary apparatus safety observation mechanism and conclusion. State why the tempting alternative is too strong, incomplete or about a different stage.
CHAPTER 8 OF 12 · Back to contents
8. Audit the component paths
Identify salt and water, state which component leaves and in what state, describe concentration or crystal formation, conserve the non-volatile salt within the boundary and match the apparatus to the desired product.
Build the explanation by naming the salt solution container temperature exposed surface desired product and safety boundary and the escape of water particles into the air while non-volatile salt particles remain in the solution. A remembered keyword is not enough: connect the observation to the mechanism and identify what would have to change for the conclusion to change.
Repair the nearest misconception by checking whether an observation shows concentration crystal formation complete dryness or recovery of a separate component and returning to solution solute solvent salt water evaporation vapour concentration saturated crystal residue dissolved particle surface heating boiling condensation distillation mass boundary apparatus safety observation mechanism and conclusion. State why the tempting alternative is too strong, incomplete or about a different stage.
CHAPTER 9 OF 12 · Back to contents
9. Worked examples
Worked case 1: Which component leaves salt solution during evaporation?
Controlled answer. Water. Water particles leave the surface as water vapour.
Mechanism. Identify the exact relationship, apply the relevant rule and preserve every stated condition. A surface clue may be compatible with several explanations, so the answer must show what makes this case decisive.
Misconception repair. Do not turn partial evidence into complete proof. Name the closest wrong answer, identify its missing condition and explain why the observed evidence supports the narrower conclusion.
Transfer. Name the state of the escaping water. Solve the altered case from the mechanism rather than copying the previous wording.
Explanation standard. A complete explanation names the observation, connects it to the rule and limits the conclusion to what follows. It should remain valid if decorative details are removed. If the explanation depends on the story topic instead of the decisive relation, rebuild it.
Audit. Recheck the salt solution container temperature exposed surface desired product and safety boundary, the escape of water particles into the air while non-volatile salt particles remain in the solution, whether an observation shows concentration crystal formation complete dryness or recovery of a separate component, solution solute solvent salt water evaporation vapour concentration saturated crystal residue dissolved particle surface heating boiling condensation distillation mass boundary apparatus safety observation mechanism and conclusion. Decide whether the evidence proves the conclusion or only supports a limited statement.
Worked case 2: What happens to the dissolved salt?
Controlled answer. It remains in the container. The salt is non-volatile under the stated conditions.
Mechanism. Identify the exact relationship, apply the relevant rule and preserve every stated condition. A surface clue may be compatible with several explanations, so the answer must show what makes this case decisive.
Misconception repair. Do not turn partial evidence into complete proof. Name the closest wrong answer, identify its missing condition and explain why the observed evidence supports the narrower conclusion.
Transfer. Trace it as water volume decreases. Solve the altered case from the mechanism rather than copying the previous wording.
Explanation standard. A complete explanation names the observation, connects it to the rule and limits the conclusion to what follows. It should remain valid if decorative details are removed. If the explanation depends on the story topic instead of the decisive relation, rebuild it.
Audit. Recheck the salt solution container temperature exposed surface desired product and safety boundary, the escape of water particles into the air while non-volatile salt particles remain in the solution, whether an observation shows concentration crystal formation complete dryness or recovery of a separate component, solution solute solvent salt water evaporation vapour concentration saturated crystal residue dissolved particle surface heating boiling condensation distillation mass boundary apparatus safety observation mechanism and conclusion. Decide whether the evidence proves the conclusion or only supports a limited statement.
Worked case 3: Why does the solution become more concentrated?
Controlled answer. The amount of water decreases while the salt remains. More salt is present per unit volume of solution.
Mechanism. Identify the exact relationship, apply the relevant rule and preserve every stated condition. A surface clue may be compatible with several explanations, so the answer must show what makes this case decisive.
Misconception repair. Do not turn partial evidence into complete proof. Name the closest wrong answer, identify its missing condition and explain why the observed evidence supports the narrower conclusion.
Transfer. Do not say extra salt is created. Solve the altered case from the mechanism rather than copying the previous wording.
Explanation standard. A complete explanation names the observation, connects it to the rule and limits the conclusion to what follows. It should remain valid if decorative details are removed. If the explanation depends on the story topic instead of the decisive relation, rebuild it.
Audit. Recheck the salt solution container temperature exposed surface desired product and safety boundary, the escape of water particles into the air while non-volatile salt particles remain in the solution, whether an observation shows concentration crystal formation complete dryness or recovery of a separate component, solution solute solvent salt water evaporation vapour concentration saturated crystal residue dissolved particle surface heating boiling condensation distillation mass boundary apparatus safety observation mechanism and conclusion. Decide whether the evidence proves the conclusion or only supports a limited statement.
Worked case 4: Repair: salt evaporates together with the water.
Controlled answer. Water evaporates while the dissolved salt remains. The components have different volatility under ordinary conditions.
Mechanism. Identify the exact relationship, apply the relevant rule and preserve every stated condition. A surface clue may be compatible with several explanations, so the answer must show what makes this case decisive.
Misconception repair. Do not turn partial evidence into complete proof. Name the closest wrong answer, identify its missing condition and explain why the observed evidence supports the narrower conclusion.
Transfer. State what could later be observed in the dish. Solve the altered case from the mechanism rather than copying the previous wording.
Explanation standard. A complete explanation names the observation, connects it to the rule and limits the conclusion to what follows. It should remain valid if decorative details are removed. If the explanation depends on the story topic instead of the decisive relation, rebuild it.
Audit. Recheck the salt solution container temperature exposed surface desired product and safety boundary, the escape of water particles into the air while non-volatile salt particles remain in the solution, whether an observation shows concentration crystal formation complete dryness or recovery of a separate component, solution solute solvent salt water evaporation vapour concentration saturated crystal residue dissolved particle surface heating boiling condensation distillation mass boundary apparatus safety observation mechanism and conclusion. Decide whether the evidence proves the conclusion or only supports a limited statement.
Worked case 5: Can filtration remove dissolved salt first?
Controlled answer. No. Dissolved salt passes through ordinary filter paper with the water.
Mechanism. Identify the exact relationship, apply the relevant rule and preserve every stated condition. A surface clue may be compatible with several explanations, so the answer must show what makes this case decisive.
Misconception repair. Do not turn partial evidence into complete proof. Name the closest wrong answer, identify its missing condition and explain why the observed evidence supports the narrower conclusion.
Transfer. Use evaporation or crystallisation for salt recovery. Solve the altered case from the mechanism rather than copying the previous wording.
Explanation standard. A complete explanation names the observation, connects it to the rule and limits the conclusion to what follows. It should remain valid if decorative details are removed. If the explanation depends on the story topic instead of the decisive relation, rebuild it.
Audit. Recheck the salt solution container temperature exposed surface desired product and safety boundary, the escape of water particles into the air while non-volatile salt particles remain in the solution, whether an observation shows concentration crystal formation complete dryness or recovery of a separate component, solution solute solvent salt water evaporation vapour concentration saturated crystal residue dissolved particle surface heating boiling condensation distillation mass boundary apparatus safety observation mechanism and conclusion. Decide whether the evidence proves the conclusion or only supports a limited statement.
Worked case 6: What may appear when enough water is removed?
Controlled answer. Salt crystals. A concentrated or saturated solution can deposit solid salt.
Mechanism. Identify the exact relationship, apply the relevant rule and preserve every stated condition. A surface clue may be compatible with several explanations, so the answer must show what makes this case decisive.
Misconception repair. Do not turn partial evidence into complete proof. Name the closest wrong answer, identify its missing condition and explain why the observed evidence supports the narrower conclusion.
Transfer. Distinguish crystals from undissolved dirt. Solve the altered case from the mechanism rather than copying the previous wording.
Explanation standard. A complete explanation names the observation, connects it to the rule and limits the conclusion to what follows. It should remain valid if decorative details are removed. If the explanation depends on the story topic instead of the decisive relation, rebuild it.
Audit. Recheck the salt solution container temperature exposed surface desired product and safety boundary, the escape of water particles into the air while non-volatile salt particles remain in the solution, whether an observation shows concentration crystal formation complete dryness or recovery of a separate component, solution solute solvent salt water evaporation vapour concentration saturated crystal residue dissolved particle surface heating boiling condensation distillation mass boundary apparatus safety observation mechanism and conclusion. Decide whether the evidence proves the conclusion or only supports a limited statement.
Worked case 7: Does evaporation require boiling?
Controlled answer. No. Evaporation can occur at the surface below the boiling point.
Mechanism. Identify the exact relationship, apply the relevant rule and preserve every stated condition. A surface clue may be compatible with several explanations, so the answer must show what makes this case decisive.
Misconception repair. Do not turn partial evidence into complete proof. Name the closest wrong answer, identify its missing condition and explain why the observed evidence supports the narrower conclusion.
Transfer. Compare slow room-temperature evaporation with heating. Solve the altered case from the mechanism rather than copying the previous wording.
Explanation standard. A complete explanation names the observation, connects it to the rule and limits the conclusion to what follows. It should remain valid if decorative details are removed. If the explanation depends on the story topic instead of the decisive relation, rebuild it.
Audit. Recheck the salt solution container temperature exposed surface desired product and safety boundary, the escape of water particles into the air while non-volatile salt particles remain in the solution, whether an observation shows concentration crystal formation complete dryness or recovery of a separate component, solution solute solvent salt water evaporation vapour concentration saturated crystal residue dissolved particle surface heating boiling condensation distillation mass boundary apparatus safety observation mechanism and conclusion. Decide whether the evidence proves the conclusion or only supports a limited statement.
Worked case 8: Why can gentle heating speed evaporation?
Controlled answer. It can increase the energy of water particles and the rate at which they leave the surface. Heating affects rate without making salt the evaporating component.
Mechanism. Identify the exact relationship, apply the relevant rule and preserve every stated condition. A surface clue may be compatible with several explanations, so the answer must show what makes this case decisive.
Misconception repair. Do not turn partial evidence into complete proof. Name the closest wrong answer, identify its missing condition and explain why the observed evidence supports the narrower conclusion.
Transfer. Keep the safety boundary visible. Solve the altered case from the mechanism rather than copying the previous wording.
Explanation standard. A complete explanation names the observation, connects it to the rule and limits the conclusion to what follows. It should remain valid if decorative details are removed. If the explanation depends on the story topic instead of the decisive relation, rebuild it.
Audit. Recheck the salt solution container temperature exposed surface desired product and safety boundary, the escape of water particles into the air while non-volatile salt particles remain in the solution, whether an observation shows concentration crystal formation complete dryness or recovery of a separate component, solution solute solvent salt water evaporation vapour concentration saturated crystal residue dissolved particle surface heating boiling condensation distillation mass boundary apparatus safety observation mechanism and conclusion. Decide whether the evidence proves the conclusion or only supports a limited statement.
Worked case 9: Is visible white mist the water vapour itself?
Controlled answer. Not necessarily; visible mist consists of tiny liquid droplets. Water vapour is a gas and is invisible.
Mechanism. Identify the exact relationship, apply the relevant rule and preserve every stated condition. A surface clue may be compatible with several explanations, so the answer must show what makes this case decisive.
Misconception repair. Do not turn partial evidence into complete proof. Name the closest wrong answer, identify its missing condition and explain why the observed evidence supports the narrower conclusion.
Transfer. Separate the escaping gas from later condensation. Solve the altered case from the mechanism rather than copying the previous wording.
Explanation standard. A complete explanation names the observation, connects it to the rule and limits the conclusion to what follows. It should remain valid if decorative details are removed. If the explanation depends on the story topic instead of the decisive relation, rebuild it.
Audit. Recheck the salt solution container temperature exposed surface desired product and safety boundary, the escape of water particles into the air while non-volatile salt particles remain in the solution, whether an observation shows concentration crystal formation complete dryness or recovery of a separate component, solution solute solvent salt water evaporation vapour concentration saturated crystal residue dissolved particle surface heating boiling condensation distillation mass boundary apparatus safety observation mechanism and conclusion. Decide whether the evidence proves the conclusion or only supports a limited statement.
Worked case 10: If all visible liquid is gone, has the salt disappeared?
Controlled answer. No. The non-volatile salt remains as solid residue or crystals.
Mechanism. Identify the exact relationship, apply the relevant rule and preserve every stated condition. A surface clue may be compatible with several explanations, so the answer must show what makes this case decisive.
Misconception repair. Do not turn partial evidence into complete proof. Name the closest wrong answer, identify its missing condition and explain why the observed evidence supports the narrower conclusion.
Transfer. Check the container rather than only the liquid level. Solve the altered case from the mechanism rather than copying the previous wording.
Explanation standard. A complete explanation names the observation, connects it to the rule and limits the conclusion to what follows. It should remain valid if decorative details are removed. If the explanation depends on the story topic instead of the decisive relation, rebuild it.
Audit. Recheck the salt solution container temperature exposed surface desired product and safety boundary, the escape of water particles into the air while non-volatile salt particles remain in the solution, whether an observation shows concentration crystal formation complete dryness or recovery of a separate component, solution solute solvent salt water evaporation vapour concentration saturated crystal residue dissolved particle surface heating boiling condensation distillation mass boundary apparatus safety observation mechanism and conclusion. Decide whether the evidence proves the conclusion or only supports a limited statement.
Worked case 11: A learner wants both salt and liquid water. Is an open evaporating dish enough?
Controlled answer. No. It can leave salt but lets water vapour escape into the surroundings.
Mechanism. Identify the exact relationship, apply the relevant rule and preserve every stated condition. A surface clue may be compatible with several explanations, so the answer must show what makes this case decisive.
Misconception repair. Do not turn partial evidence into complete proof. Name the closest wrong answer, identify its missing condition and explain why the observed evidence supports the narrower conclusion.
Transfer. Use condensation in a suitable collection system for water recovery. Solve the altered case from the mechanism rather than copying the previous wording.
Explanation standard. A complete explanation names the observation, connects it to the rule and limits the conclusion to what follows. It should remain valid if decorative details are removed. If the explanation depends on the story topic instead of the decisive relation, rebuild it.
Audit. Recheck the salt solution container temperature exposed surface desired product and safety boundary, the escape of water particles into the air while non-volatile salt particles remain in the solution, whether an observation shows concentration crystal formation complete dryness or recovery of a separate component, solution solute solvent salt water evaporation vapour concentration saturated crystal residue dissolved particle surface heating boiling condensation distillation mass boundary apparatus safety observation mechanism and conclusion. Decide whether the evidence proves the conclusion or only supports a limited statement.
Worked case 12: What does a smaller volume of solution prove?
Controlled answer. Some solvent has left or been removed. It does not by itself prove the exact amount of salt or that crystals have formed.
Mechanism. Identify the exact relationship, apply the relevant rule and preserve every stated condition. A surface clue may be compatible with several explanations, so the answer must show what makes this case decisive.
Misconception repair. Do not turn partial evidence into complete proof. Name the closest wrong answer, identify its missing condition and explain why the observed evidence supports the narrower conclusion.
Transfer. Keep observation and inference separate. Solve the altered case from the mechanism rather than copying the previous wording.
Explanation standard. A complete explanation names the observation, connects it to the rule and limits the conclusion to what follows. It should remain valid if decorative details are removed. If the explanation depends on the story topic instead of the decisive relation, rebuild it.
Audit. Recheck the salt solution container temperature exposed surface desired product and safety boundary, the escape of water particles into the air while non-volatile salt particles remain in the solution, whether an observation shows concentration crystal formation complete dryness or recovery of a separate component, solution solute solvent salt water evaporation vapour concentration saturated crystal residue dissolved particle surface heating boiling condensation distillation mass boundary apparatus safety observation mechanism and conclusion. Decide whether the evidence proves the conclusion or only supports a limited statement.
CHAPTER 10 OF 12 · Back to contents
10. Independent practice
Practice 1: Why does salt sometimes crystallise on the container edge?
Explained answer. Solution reaching the edge can lose water and become sufficiently concentrated for crystals to form. The salt was transported in solution before water evaporated.
Delayed transfer. Trace the two components. Cover the answer later and rebuild the chain.
Control question. Which exact condition does the nearest wrong answer miss? State it before checking.
Extension. Change one decisive feature while keeping the story similar. Explain why the conclusion now stays or changes.
Independent proof. Restate the answer without copying its wording. Your version must identify the evidence, the governing relationship and the boundary of the claim. Then write one fact that would be relevant but still insufficient on its own. This separates explanation from repetition.
Delayed comparison. Save this item beside the near-nonexample you created. On the next attempt, compare them before answering and point to the single feature that controls the difference. If more than one feature changed, revise the pair so the comparison stays fair.
Practice 2: Can the mass inside an open dish decrease?
Explained answer. Yes. Water vapour leaves the chosen dish boundary and enters the surroundings.
Delayed transfer. Define the system before applying conservation. Cover the answer later and rebuild the chain.
Control question. Which exact condition does the nearest wrong answer miss? State it before checking.
Extension. Change one decisive feature while keeping the story similar. Explain why the conclusion now stays or changes.
Independent proof. Restate the answer without copying its wording. Your version must identify the evidence, the governing relationship and the boundary of the claim. Then write one fact that would be relevant but still insufficient on its own. This separates explanation from repetition.
Delayed comparison. Save this item beside the near-nonexample you created. On the next attempt, compare them before answering and point to the single feature that controls the difference. If more than one feature changed, revise the pair so the comparison stays fair.
Practice 3: If the dish and surrounding captured vapour form a closed measured system, what happens to total matter?
Explained answer. It is conserved within the complete system. Water changes location and state rather than vanishing.
Delayed transfer. Include every component in the boundary. Cover the answer later and rebuild the chain.
Control question. Which exact condition does the nearest wrong answer miss? State it before checking.
Extension. Change one decisive feature while keeping the story similar. Explain why the conclusion now stays or changes.
Independent proof. Restate the answer without copying its wording. Your version must identify the evidence, the governing relationship and the boundary of the claim. Then write one fact that would be relevant but still insufficient on its own. This separates explanation from repetition.
Delayed comparison. Save this item beside the near-nonexample you created. On the next attempt, compare them before answering and point to the single feature that controls the difference. If more than one feature changed, revise the pair so the comparison stays fair.
Practice 4: What is the residue after complete evaporation of clean salt solution?
Explained answer. Salt. The solvent has left while the solute remains.
Delayed transfer. Avoid calling the residue water. Cover the answer later and rebuild the chain.
Control question. Which exact condition does the nearest wrong answer miss? State it before checking.
Extension. Change one decisive feature while keeping the story similar. Explain why the conclusion now stays or changes.
Independent proof. Restate the answer without copying its wording. Your version must identify the evidence, the governing relationship and the boundary of the claim. Then write one fact that would be relevant but still insufficient on its own. This separates explanation from repetition.
Delayed comparison. Save this item beside the near-nonexample you created. On the next attempt, compare them before answering and point to the single feature that controls the difference. If more than one feature changed, revise the pair so the comparison stays fair.
Practice 5: How can concentration be compared fairly?
Explained answer. Use equal sample volumes or measure solute-to-solution relationships under controlled conditions. Darker appearance alone may not apply to colourless salt solution.
Delayed transfer. Choose measurable evidence. Cover the answer later and rebuild the chain.
Control question. Which exact condition does the nearest wrong answer miss? State it before checking.
Extension. Change one decisive feature while keeping the story similar. Explain why the conclusion now stays or changes.
Independent proof. Restate the answer without copying its wording. Your version must identify the evidence, the governing relationship and the boundary of the claim. Then write one fact that would be relevant but still insufficient on its own. This separates explanation from repetition.
Delayed comparison. Save this item beside the near-nonexample you created. On the next attempt, compare them before answering and point to the single feature that controls the difference. If more than one feature changed, revise the pair so the comparison stays fair.
Practice 6: Why is evaporation suitable for recovering salt?
Explained answer. The solvent is volatile under the conditions while salt is not. The property difference enables separation.
Delayed transfer. Name the property rather than only the apparatus. Cover the answer later and rebuild the chain.
Control question. Which exact condition does the nearest wrong answer miss? State it before checking.
Extension. Change one decisive feature while keeping the story similar. Explain why the conclusion now stays or changes.
Independent proof. Restate the answer without copying its wording. Your version must identify the evidence, the governing relationship and the boundary of the claim. Then write one fact that would be relevant but still insufficient on its own. This separates explanation from repetition.
Delayed comparison. Save this item beside the near-nonexample you created. On the next attempt, compare them before answering and point to the single feature that controls the difference. If more than one feature changed, revise the pair so the comparison stays fair.
Practice 7: What is the fastest exam chain?
Explained answer. Salt solution contains dissolved salt and water; water evaporates as vapour; salt remains; concentration rises and crystals may form. The sequence preserves component identity and state change.
Delayed transfer. Add apparatus details only when requested. Cover the answer later and rebuild the chain.
Control question. Which exact condition does the nearest wrong answer miss? State it before checking.
Extension. Change one decisive feature while keeping the story similar. Explain why the conclusion now stays or changes.
Independent proof. Restate the answer without copying its wording. Your version must identify the evidence, the governing relationship and the boundary of the claim. Then write one fact that would be relevant but still insufficient on its own. This separates explanation from repetition.
Delayed comparison. Save this item beside the near-nonexample you created. On the next attempt, compare them before answering and point to the single feature that controls the difference. If more than one feature changed, revise the pair so the comparison stays fair.
Practice 8: State the full method.
Explained answer. Identify solute and solvent, define the system boundary, trace water leaving the surface as vapour, keep non-volatile salt in the container, explain rising concentration and possible crystallisation, distinguish evaporation from filtration, and add condensation only when liquid water must also be recovered. The method connects particle path, separation property, observation and product choice.
Delayed transfer. Apply it after a delayed mixed separation question. Cover the answer later and rebuild the chain.
Control question. Which exact condition does the nearest wrong answer miss? State it before checking.
Extension. Change one decisive feature while keeping the story similar. Explain why the conclusion now stays or changes.
Independent proof. Restate the answer without copying its wording. Your version must identify the evidence, the governing relationship and the boundary of the claim. Then write one fact that would be relevant but still insufficient on its own. This separates explanation from repetition.
Delayed comparison. Save this item beside the near-nonexample you created. On the next attempt, compare them before answering and point to the single feature that controls the difference. If more than one feature changed, revise the pair so the comparison stays fair.
CHAPTER 11 OF 12 · Back to contents
11. Delayed transfer
On day one, solve clear examples. On day three, mix examples, near-nonexamples and incomplete evidence. On day seven, solve without headings or a word bank. Delay reveals whether the method can be reconstructed independently.
Keep an error log for the first failed stage: reading, representation, rule, execution or checking. The earliest failure identifies the repair.
Interleave this skill with neighbouring ideas that share vocabulary. Classify each item only after naming the distinguishing condition.
In timed work, mark the relationship, apply the rule, write the conclusion and audit one condition. If checking changes the answer, record the overlooked feature.
Create a teach-back card with a near-nonexample on the front and the repaired mechanism on the back. Explain why the tempting answer fails.
Finish with one basic example, one boundary case and one transfer case. Supply explanations that a classmate can verify.
For a second delayed test, reverse the direction: start from a conclusion and invent evidence that would justify it, then evidence that would be insufficient. This exposes the boundary between relevance and proof.
CHAPTER 12 OF 12 · Back to contents
12. Family guidance and FAQs
Guidance for parents and tutors
Ask for the decisive condition before confirming the answer. Use prompts such as “What exactly happened?”, “Which stage or meaning is this?” and “What would prove it?”
Fade support from labelled examples to mixed questions and delayed open response. Independent retrieval after time and topic change is the target.
Praise precise claim control. Narrowing an answer when evidence is incomplete is scientific and academic strength.
Frequently asked questions
Should I memorise the rule?
Memorise the compact rule, then practise examples and near-nonexamples so the conditions remain visible.
What if two answers seem possible?
Return to the exact relationship and choose the option satisfying every stated condition without adding facts.
Why delay practice?
Immediate repetition may depend on the recent explanation; delay tests reconstruction.
How should an error be corrected?
Name the first failed stage and practise it with a changed example.
When is the skill ready?
When the learner can explain, apply and transfer it after a delay.
What is the final audit?
Check relationship, mechanism, claim strength and whole-question fit.
Next routes
Continue at the Science learning hub or return to the series directory.