Mention with reason the colour changes observed when :
copper powder is strongly heated in the presence of oxygen

Explanation

**Step-by-Step Solution:**

1. **Identify the Initial Substance:**
- Copper powder is the starting material, which is typically shiny and has an orange-brown color.

2. **Understand the Reaction:**
- When copper powder is heated in the presence of oxygen (which is available in the atmosphere), it undergoes a chemical reaction. The reaction can be represented as:
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