Offline Classroom Activities — Science 6
Term 1 · Week 3 · CG Quarter 1, competency 3 · Reversible and irreversible changes
Three individual and two group activities. No electricity, nothing to buy, no laboratory equipment, and nothing lit. All five are written for a room of 45 or more with fixed desks.
The best evidence in this week takes three days to arrive. Two of the five activities are set up on Monday and read on Friday, and the waiting is not a scheduling inconvenience — it is what turns a claim the teacher made into an observation the class made.
Activity 1 — Four Saucers (individual, runs all week)
| Time | 15 minutes on Monday, 2 minutes a day, 15 minutes on Friday |
| Materials | Four saucers or jar lids per group; salt; sugar; sand; a small piece of bread |
| Preparation | Ten minutes: collect lids, and find the sunniest surface in the room. |
Instructions
- Saucer 1: salt water, stirred until clear. Saucer 2: sugar water, stirred until clear. Saucer 3: sand in water, stirred. Saucer 4: a piece of bread, dampened.
- Draw all four. Write one sentence for each about what you can see.
- Predict, in writing, what each will look like on Friday, and why.
- Look each day for two minutes. Record one sentence per saucer.
- On Friday, compare with the prediction.
What happens
| Saucer | Friday | The change |
|---|---|---|
| Salt water | White crystals; the salt is all back | Physical — dissolving |
| Sugar water | A sticky white or pale-brown residue; the sugar is back | Physical — dissolving |
| Sand in water | Water gone, sand exactly as it was | Physical — it never dissolved at all |
| Damp bread | Mould, or hard and discoloured | Chemical — new materials, and you cannot get bread back |
Saucer 4 is why there are four and not three. Three saucers all say physical, and a class that sees only those learns that everything comes back. The bread is the control on the whole idea.
Differentiation
| One step down | Two saucers: salt water and damp bread. The contrast is the whole point and the daily entry is one line. |
| One step up | Add a fifth: salt water in a covered container. Nothing evaporates and nothing comes back — so was the change reversible or not? The honest answer is that reversibility is about the material, not about whether anybody bothered. |
Assessment
Read the Monday prediction against the Friday entry. Three piles:
Predicted correctly with a reason · Predicted wrongly, then explained why on Friday · Wrote the same sentence on Monday and Friday
The middle pile is the successful one.
Activity 2 — The Evidence Column (individual)
| Time | 20 minutes |
| Materials | Paper and pencil |
| Preparation | Five minutes: write the ten changes on the board. |
The ten changes
- Ice melting on a plate · 2. Bread being toasted · 3. A nail bending · 4. A nail rusting ·
- Water boiling away · 6. Milk turning sour · 7. Sugar stirred into tea · 8. A candle wick burning · 9. Paper torn in half · 10. A banana going black
Instructions
- Three columns: The change · Physical or chemical · My evidence.
- Fill the third column first for every row, before writing any labels.
- Then go back and fill the second column from the third.
- Underline any row where you had to change your mind.
Why the columns are filled in that order
Filling the label first and the reason second produces a reason invented to fit the label. It is the commonest thing a learner does when a marking scheme rewards both, and it is invisible in the finished work. Filling the evidence first makes it visible, to the learner as much as to the teacher.
Differentiation
| One step down | Five changes, and the teacher supplies four possible pieces of evidence to choose from for each. |
| One step up | Add: a glass shatters and blue and yellow paint are mixed. Both defeat the easy rule and both have good answers. |
Assessment
Not a percentage. Count the rows where the evidence column says something observable.
| Seen | What it means |
|---|---|
| Eight or more observable pieces of evidence | The competency is met, and met in the right order |
| Evidence like "because it is chemical" | Circular. This is the shape to name aloud on Monday |
| Evidence column empty, labels correct | Sorting from memory. The remediation sheet |
Activity 3 — The Four Awkward Cases (individual)
| Time | 20 minutes |
| Materials | Paper; a candle if there is one, unlit; two colours of paint or chalk dust |
| Preparation | None beyond finding the candle. |
The four cases
| Case | Why it is awkward |
|---|---|
| A glass shatters | You cannot undo it, and no new material was made |
| A candle burns for an hour | Two changes of different kinds at once, on one object |
| Blue and yellow paint make green | A colour change, which is supposed to be a sign |
| Smoke rises from a fire | Partly a gas and partly solid particles; there is no clean single answer |
Instructions
- For each case, write what the easy rule says: can you undo it?
- Then write what the real question says: is it still the same material?
- Where the two disagree, write which one you would trust, and why.
- Choose the case you found hardest and write one sentence explaining the difficulty to somebody in Grade 5.
The answers, and the honesty they need
- Glass: cannot undo; same material. Physical. The real question wins.
- Candle: the wax melting and re-hardening is physical; the wick and wax burning is chemical. Both are true at once and neither cancels the other.
- Paint: cannot easily undo; both paints are still there. Physical. The colour-change sign has a qualifier — that will not wash off or separate — and this is why.
- Smoke: hot gases carrying solid soot. There is no single tidy label, and that is the correct answer, not a failure to find one.
Assessment
Step 4 is the one to read. A learner who can explain the difficulty to somebody younger has understood it; a learner who repeats the answer has not.
Activity 4 — The Evidence Court (group)
| Time | 30 minutes |
| Group size | 6 — works at 5 or 7 |
| Materials | Twelve slips per group, cut from one sheet; pencil |
| Preparation | Fifteen minutes: write the twelve changes below and cut them up, one set per group. Reusable all year. |
The twelve changes
| Change | Kind | |
|---|---|---|
| Ice melting | Physical | |
| Water boiling away | Physical | |
| Paper torn in half | Physical | |
| Salt dissolving | Physical | |
| Wax melting | Physical | |
| A glass shattering | Physical | the edge case |
| Paper burning | Chemical | |
| An egg frying | Chemical | |
| A nail rusting | Chemical | |
| Milk souring | Chemical | |
| Bread toasting | Chemical | |
| Blue and yellow paint mixing | Physical | the second edge case |
Roles — everybody has one
| Role | What they do | How many |
|---|---|---|
| Judge | The only one who may place a slip on a pile — and may not do so until evidence has been given | 1 |
| Counsel for Still There | Argues that the original material survived | 1 |
| Counsel for Something New | Argues that a new material exists, and must name which sign | 1 |
| Recorder | Writes the decision and the evidence, never the label alone | 1 |
| Challenger | Must challenge at least three decisions, whether or not they disagree | 1 |
| Timekeeper | Ninety seconds per slip | 1 |
With five, the Judge keeps time. With seven, add a Second Recorder who logs only the two edge cases and what the group said about them.
Instructions
- Shuffle the twelve slips. Draw one at a time.
- Counsel for Something New must name one of the four signs, or the argument fails. Saying it just is does not count.
- The Judge decides only after both counsels have spoken.
- The Recorder writes the kind and the evidence.
- After twelve, read out the two the group argued about longest.
The point of the game
Requiring a named sign is the whole design. Without it, chemical becomes the answer for anything dramatic and physical the answer for anything dull, and the class can play the game correctly all lesson without using the competency once.
Say at the end: "Two of the twelve are traps, and both are physical. If you got the ten easy ones and missed both traps, you have learned the examples. If you got a trap right, you used the question."
Rubric — 12 marks
| Criterion | 3 | 2 | 1 | 0 |
|---|---|---|---|---|
| Correct classification | 11 or 12, including at least one trap | 9 or 10 | 6 to 8 | Fewer than 6 |
| Evidence recorded | Every slip has a named sign or a named recovery | Most do | Some do | Labels only |
| Challenges | Three or more, each answered | Two | One | None |
| Everybody worked | All six spoke | Five | Four | Three or fewer |
Activity 5 — Get It Back (group)
| Time | 35 minutes |
| Group size | 5 — works at 4 or 6 |
| Materials | One mixture per group, plus whatever it needs: salt water and a saucer; sand in water, cloth and a jar; iron filings or small nails in sawdust and a magnet; rice with small stones; rice with husks and a tray |
| Preparation | Twenty minutes to make up five mixtures. All five are reusable except the salt water. |
Roles — everybody has one
| Role | What they do | How many |
|---|---|---|
| Planner | Writes the method before anything is touched, in numbered steps | 1 |
| Operator | Carries out the method. May not improvise without telling the Recorder | 1 |
| Measurer | Weighs or measures what went in and what came out, with units | 1 |
| Recorder | Writes what actually happened, including the departures from the plan | 1 |
| Reporter | Tells the class the method, the recovery, and what was lost | 1 |
With four, the Measurer and the Recorder combine. With six, add a Second Operator who repeats the method independently — and comparing the two recoveries is the best version of this activity, because it is replication arriving four weeks before Week 7 names it.
Instructions
- Look at your mixture. Name the two materials in it.
- The Planner writes a numbered method. Nothing may be touched until it is written.
- The Measurer records what went in.
- The Operator carries out the plan. The Recorder writes any change to it and why.
- The Measurer records what came out.
- The Reporter answers three questions to the class: what did you do, what did you get back, and what did you lose.
The third question is the one that matters
Every technique loses something. Evaporation loses the water. Filtering loses whatever soaked into the cloth. Picking loses the grains you missed. A group that reports a perfect recovery has not measured, and saying so kindly is more useful than a mark.
It also sets up competency 7 directly: explain the benefits of each mixture separation technique. A benefit is only meaningful against a cost.
Rubric — 12 marks
| Criterion | 3 | 2 | 1 | 0 |
|---|---|---|---|---|
| Method written first | Numbered, before touching anything, and followed | Written first, partly followed | Written afterwards | Not written |
| Measured in and out | Both, with units | Both, units missing | One only | Neither |
| What was lost | Named and quantified | Named | "Nothing was lost" | Not addressed |
| Everybody worked | All five roles carried out | Four | Three | Two or fewer |
If the school has no magnet, no cloth and no sunny sill
- No magnet — swap that mixture for rice with husks and a tray: winnowing needs only moving air, and one learner fanning a folded paper is enough.
- No cloth for filtering — a folded sheet of paper with a pin-hole, or a clean plastic bottle with a hole and a plug of grass. Both are slower and both work.
- No sunny windowsill — the saucers take three days instead of one, which is why Activity 1 is set up on Monday. In the rainy season, a saucer on top of a cabinet away from the door will still dry by Friday.
- No spare saucers — bottle caps hold enough salt water to show crystals, and a class of 45 can share fifteen of them between groups.
Part of the E-turo MATATAG artifact set. Companion files:
syllabus.md · lesson-plan.md ·
lesson-plan-ilaw.md · worksheet.html