State two relevant observation
Lead nitrate crystals are heated in a hard glass test tube.

Explanation

### Step-by-Step Solution:

1. **Identify the Substance**: Lead nitrate has the chemical formula Pb(NO3)2.

2. **Heating the Substance**: When lead nitrate crystals are heated in a hard glass test tube, they undergo thermal decomposition.

3. **Decomposition Reaction**: The decomposition of lead nitrate can be represented by the following chemical equation:
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