Give one example in each case
Change which occurs on heating but cannot be reversed.

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for an example of a change that occurs when a substance is heated and cannot be reversed. This means we need to identify a process where heating leads to a permanent change.

2. **Identifying the Change**: One common example of such a change is the process of making clay pots.

3. **Describing the Process**:
- **Materials Used**: The main materials involved in making clay pots are clay and water.
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