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Chemical vs. Physical Change
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What is the Chemical vs. Physical Change game?
The Change Lab is a free chemical and physical change game for around grade 5. A physical change leaves you the same substance in a new form; a chemical change makes a substance that was not there before. Across five stations you tag the evidence you can observe, test whether a change can be reversed, sort 47 real examples, and close twelve cold cases — each ruling explained, and written into a lab notebook you keep.
- Ages 9–12
- 47 real examples
- 5 stations
- Lab notebook you keep
- Misconceptions built in
- Free, no signup
Five stations, one question
“Chemical or physical?” is not a sorting task, it is an evidence task — and a two-bucket sort hides the reasoning that the standard is actually about. Each station attacks the same question from a different direction, and every one of them explains its answer.
Station 1
Evidence Bench
A sample appears. Before ruling on it you tag every sign you would actually observe — bubbles, colour, temperature, light, smell, a new solid, a change of state, a change of shape, dissolving. Claiming a sign that is not there costs points.
Separating what you saw from what you concluded is the scientific move, and it is the one a sorting activity destroys. Splitting it into two steps also exposes the false alarms: boiling makes bubbles, food dye changes colour, and neither is a chemical change.
Station 2
Reversal Chamber
One question per sample: can you get the original substance back by ordinary means? Answer, watch the reversal run, then see what actually happens and why.
Reversibility is the strongest test available at this level and the one students reach for last. It also has honest limits, stated every round: torn paper cannot be un-torn and is still physical; a rechargeable battery runs backwards and is still chemical.
Station 3
Sample Sort
Ten samples, two answers, a streak multiplier that grows to five times, and the traps deliberately mixed in with the easy ones.
This is the original activity, kept — but drawn from a library of 47 rather than the same six, weighted so every run contains examples that catch people out, and explained afterwards rather than just marked.
Station 4
Cold Cases
Twelve scenarios — a cloudy swimming pool, a green statue, a sealed milk jug — with three clues each, revealed one at a time. Ruling on the first clue is worth 40 XP, on the third only 15.
Real evidence arrives incompletely, and the scoring makes that cost real. The first clue is always suggestive and never decisive, so the station teaches when you actually know something rather than when you have a hunch.
Station 5
Rapid Fire
Sixty seconds, as many samples as you can call, three seconds lost for every wrong answer. Unlocks once three other stations are cleared.
Speed is only useful once the reasoning is automatic, which is why it is locked at the start. The time penalty means rushing loses to thinking — the same lesson, at a different tempo.
Station 6
The lab notebook
Every sample you rule on is written up with its verdict, its reasoning, whether it reverses and which signs it shows. Filter it by chemical, physical, or the ones known to trip people up.
The notebook is a revision sheet the student builds themselves, one ruling at a time, and it is the reason to come back: 47 samples do not fit in one visit, and the counter shows exactly how many are still unstudied.
How to play
- 1
Pick a station
The lab opens straight away — no signup, no download, nothing to install. Four stations are open immediately; Rapid Fire unlocks once you have cleared three. Your rank, your XP and your notebook are saved on the device.
- 2
Make the call, then read why
Every ruling ends on an explanation: what the substance became, whether the change reverses, and — where there is one — the misconception that makes this example hard. The explanation is the lesson, so it does not skip.
- 3
Fill the notebook
Work up through five ranks, from Lab Assistant to Chief Scientist, by studying more of the 47 samples. Clearing all five stations certifies the lab; everything stays open afterwards.
What it teaches
- Evidence of chemical change
- The six classic signs — gas produced, colour change, temperature change, light, a new odour, a precipitate — and, just as important, the three observations that look like evidence and are not.
- Reversibility as a test
- Melting, freezing, dissolving and condensing all run backwards; burning, rusting and cooking do not. Learning to reach for this test, and learning where it fails, is most of the topic.
- Conservation of matter
- Ash weighs less than the log because the rest left as gas. Several samples and two cold cases turn on this, because 'it disappeared' is the commonest wrong reason a student gives.
- Substance versus appearance
- Crushed, cut, ground, shattered, dyed, whipped — dramatic changes that leave the substance untouched. Separating what a thing looks like from what it is made of is the whole distinction.
- Justifying an answer
- Cold Cases rewards ruling early, which forces a student to notice the moment a clue stops being suggestive and starts being decisive. That judgement is what an exam answer is marked on.
- The known traps
- Dissolving sugar, boiling water, shattering glass, dry ice, food colouring, stale bread, setting concrete. Each is labelled as a trap in the notebook, with the reason it fools people.
Where this sits in the curriculum
Roughly aligned to the upper-primary matter strand. Children arrive at these in their own order.
| Around | Usually can |
|---|---|
| Grade 3–4 | Sorts obvious examples: melting is physical, burning is chemical. Usually reasons from the picture rather than from the substance. |
| Grade 5 | Names the signs of a chemical change and uses reversibility deliberately. Still caught by dissolving, boiling bubbles and dramatic breakage. |
| Grade 6 | Explains that mass is conserved — ash is lighter because gases left — and separates a mixture from a compound. |
| Grade 7+ | Handles the genuinely hard cases: dry ice, alloys, batteries, concrete setting, and colour change with no reaction behind it. |
Four questions to ask while they play
The lab gives the verdict. These get the reasoning said out loud.
- “What would you have to do to get it back?” — the reversibility test, in the student's own words.
- “Is there something here that was not here before?” — the actual definition, phrased so it can be answered.
- “The bubbles — are they a new gas, or is that the water boiling?” — the single most useful follow-up in the topic.
- “Would it weigh the same afterwards? Where did the rest go?” — conservation of matter, without the phrase.
Five experiments to run with the screen off
Sugar back out of the water
Dissolve sugar in warm water, then leave the dish on a windowsill for a few days. The sugar comes back — proof that dissolving destroyed nothing.
The steel wool hand warmer
Damp steel wool in a sealed bag with a thermometer. It warms as it rusts, which is exactly what a commercial hand warmer does — and it cannot be undone.
Bicarbonate on a balance
Weigh vinegar and bicarbonate of soda, mix them in an open cup, weigh again. The loss is the carbon dioxide that left. Repeat in a sealed bottle and nothing is lost.
Two apple halves
One half plain, one brushed with lemon juice. Photograph both hourly. Cutting was physical; the browning that follows is not, and the acid slows it down.
Stale versus mouldy
Two slices of bread, one left out and one bagged damp. One goes hard and can be revived in the oven; the other cannot. Same loaf, opposite answers.
Carry on from here
States of Matter
Solid, liquid, gas — the physical changes the lab keeps referring back to.
Properties of Matter
Mass, volume and density, and how a property identifies a substance.
Mixtures and Solutions
Why dissolving is physical, and how mixtures come apart again.
The Scientific Method
Observation, hypothesis, evidence — the shape of every station in the lab.
All grade 5 science games
Ecosystems, forces, circuits, the water cycle and more.
Grade 5 wall charts
Printable posters for the classroom, including matter and change.
Frequently Asked Questions
- What is the difference between a chemical and a physical change?
- A physical change alters how a substance looks — its state, shape, size, or whether it is dissolved — while leaving the substance itself intact. A chemical change produces one or more substances that were not there before, with different properties. Ice melting is physical: it is water either way. Iron rusting is chemical: iron oxide is not iron.
- What are the signs of a chemical change?
- Six: a gas is produced, the colour changes permanently, the reaction itself gets hot or cold, light or flame is given off, a new smell appears, or a solid forms in a liquid. Any one of them is a strong hint. None is proof on its own — boiling water bubbles, and food colouring changes colour, and neither makes a new substance.
- Is dissolving sugar in water a chemical change?
- No — it is physical, and it is the example most often got wrong. The sugar looks as though it has gone, but every molecule survives intact. Evaporate the water and the sugar is left in the pan. That recovery is exactly how sea salt is harvested, and it is the proof.
- Is boiling water a chemical change?
- No. The bubbles are water vapour, which is still water; boiling only pushes the particles apart. Cool the steam on a cold surface and it drips back as liquid. Bubbles are the most over-trusted sign in the whole topic, which is why the lab includes several samples that bubble for entirely physical reasons.
- Is rusting a chemical or physical change?
- Chemical. Iron combines with oxygen and water to form iron oxide, which is a different substance with different properties — softer, flaky and reddish rather than hard and grey. It cannot be turned back into iron on a bench, and a hand warmer is the same reaction run on purpose for the heat.
- Can a chemical change ever be reversed?
- Rarely by ordinary means, which is why reversibility is such a useful test — but it is not a law. A rechargeable battery runs its reaction backwards every time it charges. Equally, plenty of physical changes cannot be undone: torn paper and shattered glass are permanent and still physical. Always finish with the real question: is there a new substance?
- What age or grade is this game for?
- Around grade 5, or roughly ages 9 to 12. Younger students can play the Sample Sort and Reversal Chamber comfortably; the Cold Cases and the tier-three samples — dry ice, alloys, setting concrete — will stretch a middle-school student and a fair number of adults.
- How long does it take?
- One station is three to six minutes. There are five, plus twelve cold cases and 47 samples in the library, so a full visit runs well past twenty minutes and most students do not see every sample on their first sitting. Rank, XP and notebook are saved on the device, so it can be picked up again.
- Is it free, and does it need an account?
- Free, with no signup, no download and no ads inside the game. It runs in any browser on a phone, tablet, laptop or classroom board. Progress is stored on the device itself, not on a server, so nothing about the student is collected.
- Can I use this in a classroom?
- Yes. The five stations map onto five separate lesson segments, and the evidence key on the lab screen works as a display. The Cold Cases station in particular is built for pairs arguing at a board — the scoring rewards committing early, which is a productive thing to disagree about. The five off-screen experiments below are all doable with kitchen materials.
- What is the lab notebook?
- A record of every sample you have ruled on, with the verdict, the reasoning, whether it reverses and which signs it shows — filterable by chemical, physical, or the examples known to catch people out. It builds itself as you play, so by the end of a few visits a student has written their own revision sheet for the topic.
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