Some of these will not go back
A clay pot falls and breaks into pieces. Every piece is still clay.
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The idea
Step 1 of 4
- A whole clay pot.
- It falls and breaks into pieces.
- The pieces are glued together.
- The joins stay. It is not the same pot.
The rule
No new substance is made. Some of these changes still cannot be undone.
Undone means the same thing comes back, close enough to use again.
Grinding means crushing into powder.
| The change | New substance? | Can we undo it? |
|---|---|---|
| Fold a sheet into a boat | No | Yes — unfold it |
| An ice cube melts | No | Yes — freeze it |
| Sugar stirred into water | No | Yes — dry it off |
| A page is crumpled | No | Yes — smooth it |
| A clay pot breaks | No | No |
| Vegetables are chopped | No | No |
| Chalk is ground to powder | No | No |
| A page is torn | No | No |
Every row says "No" for new substance. So "physical means we can undo it" is wrong. These are two separate questions.