Full chapter index

The observation is “liquid droplets appeared on the outside surface of the cold cup.” It is not yet “water leaked through the cup” or “the cold created water.” Those are explanations. Science begins by keeping the observed result separate from its possible causes.

Ask the child to point to the surface: inside, outside or both. Note when droplets first appeared, whether they grew, whether they joined and ran downward, and whether the cup was sealed. Precise location and timing matter.

Touch is a limited observation and should be used carefully. A wet outer surface can be confirmed with a dry tissue. Avoid tasting any liquid or handling cracked glass. A transparent plastic or metal cup can make the same conceptual point safely.

Write two columns: “I observed” and “I infer”. Droplets outside belong in the first. “They came from water vapour in the air” belongs in the second and needs supporting evidence.

This distinction prevents confident stories from being mistaken for direct sight. It also prepares the child for many PSLE Science explanation tasks in which evidence and mechanism must be connected.

Prepare two identical dry cups. Put cold water and ice in one; put room-temperature water in the other. Cover both openings so splashes and evaporation from inside are reduced. Dry the outer surfaces and place the cups side by side.

Ask for a prediction before waiting. If the child thinks glass leaks, they may expect both cups to become wet outside, especially if both contain water. If they understand condensation, they should predict more droplets on the colder outer surface.

Observe at regular intervals. Under humid conditions, the cold cup should usually develop outer droplets more readily. The room-temperature control may remain dry or show much less. Actual results depend on temperature, humidity, surface and time.

The comparison isolates surface temperature while keeping many other features similar. It does not prove the mechanism by itself, but it weakens a simple leakage explanation because both cups contain water and only the sufficiently cold surface shows the strong effect.

Record the prediction, observations and conclusion without changing the first entry. A wrong prediction is valuable evidence about the model that needs repair.

Air is not only oxygen and nitrogen. It also contains water vapour, an invisible gaseous form of water. The amount varies with conditions. In humid Singapore air, there is often ample water vapour available near a cold surface.

Because vapour is invisible, children may think it is absent. The droplets seem to appear from nowhere. Use other observations—mist on a bathroom mirror, dew on a cool surface or droplets on a chilled bottle—to show the pattern across different containers.

Do not say “air turns into water.” The nitrogen and oxygen do not become the droplets. Water vapour within the air changes state to liquid water.

Ask the child to complete the matter pathway: water vapour in surrounding air → cooling near the cup → liquid water on the cup. Every noun and arrow should have a role.

The pathway is a model of matter tracking. It answers “where did the water come from?” without inventing passage through solid glass.

Condensation is the change from gas to liquid. In this case, water vapour becomes liquid water. The water substance remains water; its state changes.

The cold cup does not manufacture matter. It provides a surface and conditions that cool nearby water vapour enough for liquid droplets to form. Energy is transferred from the warmer surroundings toward the colder cup and contents.

At primary level, the child can explain cooling and condensation without needing advanced humidity equations or microscopic nucleation theory. Add detail only when it clarifies the causal chain.

Pair condensation with evaporation: liquid water can become water vapour, and water vapour can become liquid water. The direction depends on conditions and energy transfer.

Ask for an example of each that is not the cup. Wet clothes drying illustrate evaporation; a misted mirror after a shower illustrates condensation. Variety checks that the word is connected to a process, not one picture.

The liquid and ice inside cool the cup wall. The outer surface then cools the thin layer of air next to it. Water vapour in that air can condense on the surface when conditions are suitable.

The cup need not be made of a mysterious “sweating” material. Different materials conduct heat at different rates and may show droplets at different speeds, but the source of the outer water can still be the surrounding air.

Compare a cold metal can and an insulated cup. The metal outer surface may cool more quickly and produce visible droplets sooner, while insulation can keep the outside warmer. The material affects heat transfer and observation, not the identity of the water source.

Ask the child to draw temperature arrows qualitatively, not as matter arrows. Energy transfer toward the colder region should not be confused with water moving through the wall.

This gives two linked but distinct chains: energy transfer creates cold surface conditions; water vapour changes state and collects there.

A transparent cup contains ice water and is sealed tightly at the top. Its outside is dried. Ten minutes later, droplets appear outside. Question: “Explain why the droplets are unlikely to have come directly from the liquid inside.”

The seal reduces splashing and vapour escaping from the opening. The cup wall is intact. Water vapour already present in the surrounding air is cooled near the outer surface and condenses there.

A child may argue that water passes through microscopic holes in glass. Ask for a comparison: if ordinary glass freely let liquid water through, a room-temperature cup should also leak, and stored liquids would not remain contained. The observed temperature dependence points elsewhere.

The strongest answer states source, condition and process: “Water vapour in the surrounding air was cooled by the cold outer surface and condensed into liquid droplets.”

Do not overclaim that one classroom setup proves absolute impermeability of every material. It provides evidence against the proposed explanation for this intact cup under these conditions.

Chill an empty dry metal cup in a refrigerator, then place it in humid room air. Droplets may form outside even though no liquid water is inside. This is a powerful comparison.

If the child thought the water must pass from the contents, the empty cup creates a contradiction. A source outside the cup is required. The surrounding air contains water vapour.

Handle chilled items safely and avoid excessive condensation near electrical equipment. The purpose is conceptual; a teacher demonstration or photograph sequence can replace home practical work.

Ask what changed between a warm empty cup and a cold empty cup. The presence of internal liquid is not necessary, but low surface temperature is important.

The conclusion should remain conditional: visible condensation depends on room humidity, surface temperature and observation time. A dry result on one day does not make the mechanism false.

Fill a sealed cup with cold water coloured blue using safe food colouring. Clear droplets form outside. Their lack of blue colour can be evidence that the outer water did not simply leak from the coloured liquid.

This comparison is intuitive but should be interpreted carefully. Colour molecules generally do not enter water vapour during ordinary evaporation, and tiny colour differences may be hard to see. Use the test as supporting evidence, not a single magical proof.

Combine it with controls: an intact cup, a sealed top, a warm coloured-water cup and a cold coloured-water cup. Multiple lines of evidence strengthen the explanation.

Ask the child to predict what would happen if a small crack existed. Blue liquid might appear locally and continuously from the crack, a different pattern from clear droplets distributed across a cold surface.

Science explanations improve when alternative causes generate distinguishable predictions.

Leakage depends on a pathway through or around the container. It may begin at a crack, seam, lid or spill point and continue while pressure and liquid remain. Condensation appears on sufficiently cold exposed surfaces in contact with moist air.

Location helps. Droplets spread across the outer wall may favour condensation; a stream from one damaged point may favour leakage. Pattern alone is not conclusive, but it guides testing.

Temperature dependence helps too. If warming the outer surface stops new droplets while the cup still contains water, condensation becomes more plausible. If a crack continues leaking regardless of surface temperature, the causes differ.

Use a table: proposed cause, prediction, observation and judgement. This prevents “I think” from standing alone.

Do not ask a child to create a crack for comparison. Use a drawing, safe pre-prepared model or discussion. Evidence can be reasoned about without unsafe damage.

The room-temperature cup acts as a comparison. Both cups contain water, have similar shape and sit in the same air; the major planned difference is temperature. More outer droplets on the colder cup support the role of cooling.

A control is not “the one where nothing happens” by definition. It is a comparison condition that helps judge the effect of the variable being investigated. It may show some change.

Keep cup material, surface area, starting dryness, location and observation time similar. If one cup sits under a fan and the other in a sheltered corner, air movement becomes another difference.

Ask why a single cold cup is weaker evidence than a matched pair. With one cup, several explanations can fit. The comparison makes one causal factor more visible.

At PSLE level, naming variables is useful when connected to the reason for control. A list of “constant variables” without understanding does not establish a fair test.

Humidity describes water vapour in the air. On a more humid day, there is more water vapour available, so visible droplets may form more readily on a cold surface under otherwise similar conditions.

In a dry air-conditioned room, the same cup may develop fewer droplets or take longer. This variation is not a failure of condensation theory; it is an expected effect of changed environmental conditions.

Ask the child to compare evidence only when conditions are recorded. Time, room, airflow and starting temperature matter. “Cup A had more water” is incomplete if it was observed twice as long.

Avoid claiming that humid air is liquid water floating visibly. Water vapour is gaseous and invisible; mist consists of tiny liquid droplets.

This distinction helps later when children discuss clouds, fog and steam-like visible plumes.

As moist air cools, it can reach conditions where condensation occurs. The temperature associated with saturation under given conditions is called the dew point. Primary explanations need not calculate it to use the idea correctly.

If the cup surface is not cold enough relative to surrounding air, visible droplets may not form. “Cold” is therefore comparative and conditional, not a magical label attached to any refrigerated object.

Use two cups at different temperatures. Predict which forms droplets first. The colder surface often reaches condensation conditions sooner, assuming similar surroundings.

Do not turn the dew point into “water vapour freezes”. Condensation produces liquid droplets; freezing is liquid to solid. Frost involves different conditions and processes.

A concise answer can remain: “The cold surface cooled nearby water vapour, causing it to condense.” Advanced vocabulary is optional unless it improves accuracy.

Water inside an open cup can evaporate, and some vapour may later condense on cooler regions. But outer droplets on a sealed cold cup do not require vapour to escape from inside. Surrounding air already supplies water vapour.

This distinction matters because a child may learn “evaporation then condensation” as a fixed sequence and insist the same liquid must first leave the cup. The water cycle is broader: water vapour can originate from many places.

Ask where room water vapour might have come from earlier—evaporation from surfaces, plants, cooking, breathing and outdoor air. The immediate source near the cup is the surrounding air, even if its history is complex.

Track only the matter relevant to the question. A complete global story is not needed to explain one droplet.

When the cup is open, prevent the child from treating possible inside evaporation as the only explanation. Use the sealed comparison to isolate the misconception.

People often say a cold glass “sweats”. The phrase describes appearance, but a cup has no sweat glands and does not perform a biological process. Scientific language should identify condensation.

Analogies can help memory while hiding mechanism. Ask, “In what way is it like sweating, and in what way is it different?” Both involve visible water on a surface; the sources and processes differ.

Human sweat is secreted by glands and evaporates to help cooling. Condensation on a cup comes from water vapour in surrounding air changing to liquid on a cold surface.

Replace the analogy after it has served its purpose: “The cup appears to sweat, but the droplets form by condensation.”

This habit—use, test and limit an analogy—supports Science learning well beyond changes of state.

In the gas state, water particles are far apart and move throughout the air. Near the colder cup, energy is transferred away from them. Under suitable conditions they come closer together to form liquid water.

Do not draw gas particles shrinking or turning into different substances. Particle size in the model stays the same; arrangement and motion change with state.

In a liquid droplet, particles remain moving and close together. The visible droplet contains enormous numbers of particles; the dots in a diagram are symbolic, not a literal magnified photograph.

Use arrows to show movement of energy separately from movement of water particles. One arrow type cannot carry every meaning.

If particle theory has not yet been formalised in the child’s current learning sequence, keep the macroscopic explanation. An accurate simple account is better than memorised microscopic language used incorrectly.

The outer droplets have mass. Their matter came from water vapour in the surrounding air. The cup system can gain liquid water on its outside while the broader room air loses a tiny amount of vapour locally.

Weighing the setup before and after is difficult to interpret because evaporation, condensation and exchange with the environment can occur. An open system complicates mass measurements.

At primary level, use qualitative conservation: water does not appear from nothing or pass through intact glass merely because it becomes visible. It changes state and location.

Ask the child to trace a single “water” label through gas and liquid states. The name stays water while the state changes.

This matter pathway also helps with drying clothes, puddles and water-cycle questions. Visibility is not the same as existence.

Question: Does lower cup temperature increase the amount of outer condensation over ten minutes? Use identical cups, equal observation time, same room location, same exposed surface and controlled starting dryness. Change starting water temperature.

Define the dependent observation. It might be mass gained by a removable dry sleeve, number of standard-sized tissue areas wetted or another feasible measure. Counting droplets alone can be unreliable because droplets merge.

Repeat trials. Surface contamination, airflow and small temperature changes can affect results. A single pair is suggestive, not a universal law.

Measure temperature where possible with appropriate equipment. Labels such as “cold” and “very cold” are less precise than recorded values, though primary investigations may remain qualitative.

State a limited conclusion: under the tested conditions, the colder cup collected more outer water. Do not claim every colder object always produces exactly proportionally more condensation.

Water may splash onto the outside while filling. Dry the cup after filling and before timing. Hands can leave moisture. Hold the cup at a designated dry area or use suitable handling.

Ice can cause overflow as it is added. A lid can trap spills near the rim. Inspect the pattern and keep the fill level safely below the top.

Two cups may differ in thickness or material. Room airflow may vary across a table. Observation times may not match. List these before interpreting a small difference.

An “error” is not the same as a wrong child. It is a feature of method or measurement that can influence results. Naming it improves the investigation.

Ask which error would make condensation look like leakage and how to reduce it. This connects method critique directly to the parent question.

Cup A is cold, sealed and dry outside. Cup B is room temperature, sealed and dry outside. Cup C is cold but has water deliberately wiped onto its outside at the start.

Cup C is not a fair condensation comparison because the starting outer moisture differs. It may still be useful to show why starting condition must be controlled.

If A develops droplets while B does not, the temperature contrast supports condensation. If both are wet immediately, investigate preparation. If neither is wet, consider humidity, temperature difference and time.

The lid helps rule down splash and inside-vapour pathways, but it does not control every variable. A thoughtful conclusion acknowledges what the design addresses.

Ask the child to choose the strongest pair and justify. Experimental design is reasoning about comparisons, not merely naming apparatus.

Question: “Explain why droplets formed on the outer surface of the cold cup.” A complete answer names source, temperature effect and change of state: “Water vapour in the surrounding air was cooled by the cold cup and condensed into liquid water on its outer surface.”

“Because the cup was cold” names a condition but not the source or process. “The water condensed” names the process but leaves unclear which water and why. “Water leaked out” proposes the wrong pathway for the stated intact setup.

Use a three-link frame: source → cause → process/result. Then remove the frame once the child can construct the chain independently.

Avoid adding unsupported claims such as “the glass has tiny holes”. Extra detail can weaken an otherwise correct answer.

Read the answer against the diagram. Every pronoun should have a clear referent, and the location “outer surface” should not disappear.

A distractor may say the cold liquid passed through the cup wall. Another may say the cup produced water because it was cold. A third may confuse evaporation with condensation. Identify the prediction each explanation makes.

If water passes through the wall, a warm cup with the same liquid should also show leakage. If cold creates water, an empty cold object would produce matter from nothing. If evaporation is claimed at the cold surface, the direction of state change is reversed.

Eliminate with reasoning, not keyword spotting. The word *cold* can appear in both correct and incorrect options.

After choosing, ask the child to rewrite the correct option as a causal chain. Recognition is easier than generation; both are useful but should not be confused.

Create one distractor from the child’s own earlier model. Explaining why it fails turns a mistake into a durable boundary.

The cold-cup event is a small-scale example of water changing between gas and liquid. In the water cycle, evaporation adds water vapour to air and condensation forms tiny liquid droplets in clouds under suitable conditions.

Do not say clouds are water vapour. Visible clouds contain tiny droplets or ice crystals; water vapour itself is invisible. This distinction mirrors the cup investigation.

The processes connect, but scale and conditions differ. A cup surface provides a local place for droplets to form, while atmospheric cooling and particles support cloud formation.

Ask the child to identify what is similar—state change—and what is different—setting, scale and pathways. Transfer should preserve mechanism without claiming the situations are identical.

Use the existing water-cycle idea to reinforce matter tracking: water moves and changes state; it does not vanish when invisible or appear from nothing when visible.

Use a photograph or safe teacher-provided setup. Spend two minutes listing only observations. Spend three minutes writing two competing explanations. Use three minutes to predict what each explanation expects in a sealed or empty cold cup.

Spend two minutes writing the source–cause–process chain. Finish by explaining why an intact warm comparison helps.

On another day, use a bathroom mirror, chilled bottle or dew photograph. Ask whether the same condensation idea applies and what conditions differ.

Keep the session focused. Long lists of definitions are less useful than one well-tested causal model.

Save the first explanation and revisit it a week later. A changed explanation without prompting is evidence of conceptual progress.

The child separates “droplets were observed” from “condensation caused them”. They name surrounding-air water vapour as the source and explain the role of the cold surface.

They design or interpret a matched comparison, keep starting surfaces dry, control observation time and avoid treating one result as absolute proof.

They distinguish condensation from evaporation, leakage, freezing and biological sweating. They can trace water matter across invisible vapour and visible liquid without saying it was created.

Test transfer with an unfamiliar context such as a misted mirror. Ask for observation, inference, evidence and mechanism. A memorised cold-cup sentence is weaker than accurate reasoning across examples.

Set an observable goal: “Write a three-link explanation and one comparison that challenges the leakage idea.”

Some materials are porous, some containers have seams, and damaged vessels can leak. The conclusion concerns an intact ordinary cup under the stated conditions; it is not a claim that every material blocks every substance forever.

Science compares explanations with evidence. Check material, damage, lid, location, colour, temperature dependence and the pattern of wetness. Different observations can support a different cause.

This nuance should not confuse the basic model. For the familiar intact cold cup, condensation from surrounding-air water vapour is the appropriate explanation for distributed outer droplets.

Teach the child to state conditions rather than use absolute language. Precision strengthens, rather than weakens, the conclusion.

Seek targeted help if the child repeatedly says cold creates water, cannot identify water vapour as a source, reverses evaporation and condensation, or gives conclusions without evidence from comparisons.

Bring original diagrams and answers. A tutor can then see whether the difficulty is vocabulary, changes of state, heat transfer, fair testing or explanation structure.

If practical work creates distraction, use still images and prediction tables first. The goal is causal reasoning, not a dramatic demonstration.

The practical outcome is a child who can observe carefully, propose alternatives, use a fair comparison, track matter and explain that water vapour in surrounding air cools and condenses on a cold outer surface.

After a warm shower, a cooler mirror may become covered with tiny droplets. Water evaporates into the bathroom air, and water vapour condenses when it meets the cooler mirror under suitable conditions.

The mirror did not leak water from behind its glass. The visible film formed on the exposed surface. Wiping a clear patch removes droplets temporarily, but new condensation may form while humid air and a cool surface remain.

Compare this with the cold cup. In both, water vapour in nearby air becomes liquid on a cooler surface. The source of humidity and exact temperature pattern differ.

Ask why a warm mirror may mist less. Its surface may not cool nearby moist air sufficiently for the same amount of condensation. Temperature difference, not “mirror material” alone, matters.

Use the comparison to test transfer. If the child can explain the mirror without mentioning liquid passing through glass, the model is becoming portable.

Place a cold, dry, sealed cup inside a clean dry transparent bag and close the bag with some air trapped inside. Droplets may form on surfaces depending on which parts become sufficiently cool. This setup makes the surrounding-air source easier to discuss.

The bag contains a limited amount of moist air. As water vapour condenses, local humidity and temperatures change. Results may differ from an uncovered cup in an open room.

Ask the child to predict whether droplets form on the cup, the inner bag surface or both. The answer depends on surface temperatures and contact with moist air, so the prediction should include reasoning rather than certainty without measurements.

The bag does not prove that air is “full of liquid”. It encloses invisible water vapour that can change state.

Use only safe, non-breakable containers and keep plastic bags away from young children. A photographed teacher demonstration can serve the same conceptual purpose.

Adding salt to an ice mixture can lower its temperature under suitable conditions. The cup’s outer surface may become colder, and condensation may appear faster or be followed by freezing if conditions permit.

The salt does not turn into outer water. It changes the thermal conditions of the mixture. Water vapour from surrounding air remains the source of condensation on the outside.

If frost forms, distinguish it from ordinary liquid droplets. Depending on conditions, water may freeze after condensing or deposit in a more complex pathway. Do not force an advanced mechanism beyond the observation.

Ask the child to identify independent variable, dependent observation and controlled features in a salt-versus-no-salt comparison. Cup material, starting dryness, room location and time should be similar.

This extension shows how one factor can affect rate or amount without changing the identity of the source process.

On a smooth surface, droplets may bead and merge visibly. On a rough or absorbent sleeve, water may spread into a thin film or soak in, making separate droplets hard to count. Appearance is not a direct measure of total amount.

Two cup materials can therefore seem to condense differently even if their surface temperatures are similar. Heat transfer, wetting and visibility all influence observation.

If the investigation asks about cup material, measure temperature and water amount carefully rather than relying only on droplet count. Keep dimensions and conditions as comparable as feasible.

At PSLE level, the central inference remains modest: an intact cold outer surface can collect water from surrounding-air vapour through condensation. Surface details affect how the result is displayed.

Ask the child why a tissue-covered cup might look dry while the tissue gains mass or feels damp. The water can be present without forming shiny beads.

Answer A: “The water in the cup became cold and passed through the glass.” Answer B: “Water vapour in the air was cooled by the cold outer surface and condensed into droplets.” Compare each claim with the evidence.

Answer A predicts that internal water and a passage through the wall are necessary. An empty chilled cup or sealed coloured-water comparison challenges those predictions. It also fails to name a plausible pathway through intact glass.

Answer B predicts stronger formation on sufficiently cold surfaces exposed to moist air. The room-temperature control, empty cold cup and other condensation examples support that pattern.

Do not choose B merely because it contains the keyword *condensed*. It is better because source, condition, process and location align with observations.

Have the child improve B further by specifying “surrounding air” and “outer surface”. Scientific answers become stronger through precise relationships, not length alone.

If the child correctly names condensation but cannot state the water source, use sealed and empty cold-cup comparisons. If they know the source but reverse evaporation and condensation, practise state-change arrows with examples.

If explanations are correct but investigation questions fail, focus on variables, controls and what each comparison rules out. If practical observations are vague, separate description from inference before discussing mechanisms.

Ask the tutor to preserve the child’s original prediction. A copied final sentence can conceal an unchanged mental model; a revised prediction on a new example is stronger evidence.

Set a one-week goal: explain the cup, a mirror and one unfamiliar cold surface using source–cause–process chains, and propose a fair comparison for leakage.

Retest under a different picture or wording. Support can fade when the child no longer needs the tutor to supply “water vapour in the air”.

Three sealed identical cups are dry outside. Cup A contains ice water, Cup B contains room-temperature water, and Cup C is empty but has been chilled. All stand in the same room for ten minutes.

Predict that A and C may form more outer condensation than B if their surfaces are sufficiently cold. Cup C is especially useful because there is no internal liquid available to leak.

Record surface temperature, starting condition, observation time and an agreed measure of outer water. Do not compare only one photograph if the cups began at different times.

If A produces more than C, possible explanations include different surface temperatures and heat capacities; it does not automatically prove that some droplets leaked from A. Check the variables before changing the mechanism.

Write the conclusion with limits: “Under these room conditions, the colder cups collected more outer water, supporting condensation from surrounding-air water vapour.” That evidence-based, bounded sentence is the scientific destination of the parent’s original question.

A cold cup gradually warms toward room conditions. Condensation may be rapid at first and then slow as the outer surface becomes less cold. Meanwhile droplets already present can merge, drip or evaporate.

Therefore, “more time” does not guarantee a simple constant increase in visible droplet count. The process rate and the way droplets are measured matter. A ten-minute comparison should use the same start time and observation schedule.

Ask the child to sketch an expected qualitative pattern: outer water may increase while the surface remains sufficiently cold, then level or decrease as warming and evaporation become important. The exact graph depends on conditions.

This extension prevents a static explanation. Condensation is a process occurring in a changing thermal system, not a label applied once to a photograph.

At primary level, no exact curve is required. The child should simply connect changing temperature difference to changing evidence over time.

Children sometimes say “cold air cannot hold water” as an absolute rule. A more careful primary explanation is that cooling moist air can lead to condensation when suitable conditions are reached. The amount of water vapour and the temperature both matter.

Do not describe vapour as dissolved in air exactly like sugar in water. Air–water behaviour is more complex, and the analogy can create new misconceptions. Use observable conditions and state change.

Ask why a cold cup may remain dry in very dry air. There may be too little water vapour, or the surface may not be cold enough for visible condensation within the observation time.

Conversely, a mildly cool surface in very humid air may mist. “Cold” alone is not the full cause; it participates in a relationship with surrounding conditions.

This precision helps the child write explanations that are accurate without exceeding the expected level of detail.

Name the observation: liquid droplets on the outer surface. Name the source: water vapour in surrounding air. Name the condition: the cold cup cools nearby vapour. Name the process: condensation from gas to liquid.

Then test alternatives. A sealed or empty cold cup challenges leakage from internal liquid. A room-temperature comparison tests the role of cooling. A dry start reduces the possibility of an unnoticed spill.

State evidence with limits. The comparison supports condensation under the tested conditions; it does not prove that every wet container is intact or that every material is impermeable.

Track matter and energy separately. Water matter moves from surrounding vapour into liquid droplets, while energy is transferred from warmer surroundings toward colder regions.

When your child can build that explanation from a new photograph, propose a fair comparison and reject an unsupported leakage claim, the original tutor question has done its job.

A sealed cold lunchbox is removed from a refrigerator and becomes wet outside on a humid day. Apply the same reasoning without mentioning a cup. The observed liquid is on the exterior; surrounding-air water vapour is a possible source; the cold surface supplies conditions for condensation.

Propose a comparison with an identical room-temperature lunchbox in the same location for the same time. Dry both at the start. If the colder one develops more outer moisture, the pattern supports the temperature-based explanation.

Check alternative causes such as a leaking ice pack, an unsealed lid or water left after washing. Evidence should distinguish them: source location, colour, smell where safe to observe, repeated pattern and condition of the container.

Write the answer in one precise sentence, then expand it into observation, evidence and mechanism. The short version demonstrates clarity; the expanded version demonstrates reasoning.

Successful transfer shows that the child has learned condensation as a causal model rather than memorised “cold cup equals water droplets”.