Today you put your skills to the test. You'll watch a series of real changes and record careful, scientific observations — then classify each one. This is an assessed task.
Before we begin, let's pin up everything you'll need. Keep this in mind as you watch each change.
A good scientific observation is specific — it uses your senses and describes exactly what you notice. Let's see the difference.
| Change | Weak observation | Strong observation |
|---|---|---|
| Melting butter | "It melted." | "The solid yellow butter slowly turned into a clear yellow liquid when heated." |
| Fizzing tablet | "It bubbled." | "Bubbles of gas rose quickly to the surface and the tablet shrank until it disappeared." |
Here's the grid you'll complete for every demonstration. Let's model one row together using melting butter.
| Column | What goes here | Example (melting butter) |
|---|---|---|
| Observation | Detailed, sensory description | Solid butter turned to clear liquid when heated |
| Classification | Reversible or irreversible | Reversible |
| New substance? | Yes/no + how you can tell | No — cooling turns it solid again |
| Risk | One safety risk + how to reduce it | Hot surface — use a heat mat, don't touch |
We'll do the first change together so the routine is clear — then you're on your own for the rest.
Now work independently. Complete your results grid for each demonstration. This is your assessment evidence.
Pencils down. Let's check the correct classifications together so you know how you went.
| Change | Answer | Why |
|---|---|---|
| Melting butter | Reversible | Same substance — cooling reverses it |
| Toasting bread | Irreversible | New substance — colour & smell change |
| Popping popcorn | Irreversible | Water bursts the kernel — can't undo |
| Ice melt/refreeze | Reversible | Still H₂O the whole time |
| Burning paper | Irreversible | New substances: ash, smoke, gas |