◆ Materials · Quarter 1

Can You Get It Back?

One question sorts almost every change you will ever see. Almost.

A saucer of salt water goes on the windowsill now. Do not explain it. 1 min

Four things that happened this morning

Ice melted in a glass.
Rice was cooked.
A shirt dried on the line.
A slice of mango turned brown.

Which of these could be undone?

Take a vote on each. Write the counts. Settle nothing. 5 min

The question the curriculum asks

Not which is which — you can memorise that.
Why. The reason is the lesson.

Why are physical changes reversible and chemical changes irreversible?

This is competency 3 word for word. Read it aloud. 3 min

Physical change

What happens

The material is rearranged. Melted, dissolved, torn, bent, evaporated.

Why you can undo it

The material is still there. Nothing was used up and nothing new was made. Put the energy back the other way and it returns.

Slide 4 and 5 are the wall chart's first two panels. 4 min

Chemical change

What happens

The materials are used up and different ones appear. Burning, rusting, cooking, rotting.

Why you cannot undo it

The old material is gone. There is nothing to put back. Cooling the ash does not make paper.

Ask for one example of each from the room before moving on. 4 min

The sugar problem

Sugar stirred into water disappears completely.
Nothing is left to see. It looks like the biggest change on the list.

New material, or the same one?

Most classes say new. Do not correct. Point at the windowsill. 4 min

The evidence

Taste it — still sweet.
Boil the water off — the sugar comes back, every grain of it.
Disappearing is not the same as being destroyed.

So which kind of change is dissolving?

Physical. The saucer on the windowsill will prove it on Friday. 4 min

The burning problem

Paper burns. Ash is left behind.
Some learners say: the ash is still there, so nothing was lost.

Try writing on the ash. What happened to the paper?

Ash is not paper. It is one of the new materials the fire made. 4 min

Four signs a new material was made

A colour change that will not wash off
A gas — bubbles, fizzing, smoke
Heat or light given off
A solid appearing in a clear liquid

Grade 4 met these. Grade 6 uses them as evidence rather than as a list. 4 min

Now the hard one

A glass is dropped and shatters.

Can you get it back?

No. Let them sit with that for a moment before slide 11. 3 min

Two tests, and they disagree

Can you undo it?

No. Nobody can un-shatter a glass.

Was a new material made?

No. Every piece is still glass. Melt them down and you have glass again.

So which kind of change is it?

Physical. The second test is the real one; the first is a good shortcut that has an edge. 5 min

So what is the real test?

Can you get it back is a good question and usually gives the right answer.
When the two disagree, the new-material question wins.

Is there a new material, or the same material rearranged?

This distinction is the difference between a Grade 6 answer and a Grade 4 one. 4 min

Getting it back on purpose

Salt from seawater — evaporation
Rice from stones — picking
Sand from water — decantation or filtering
Iron nails from sawdust — using a magnet

Which of these would work on sugar in tea?

Evaporation. This is competency 6 arriving in Week 5 — flag it forward. 4 min

Back to this morning

Physical

Ice melting · a shirt drying

Chemical

Rice cooking · mango browning

Does everybody agree now? Say why, not which.

Take the vote again and compare with slide 2. 4 min

One sentence to leave with

Not "can I undo it" — "is it still the same material?"

Say it together. It is on the worksheet and on the wall chart. 2 min