Assertion : On heating ferromagnetic or ferromagnetic substance , they become paramagnetic
Reason :The electrons change their spin on heating

Explanation

To solve the question regarding the assertion and reason about ferromagnetic and paramagnetic substances, we will analyze both statements step by step.

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that "On heating ferromagnetic or antiferromagnetic substances, they become paramagnetic."
- Ferromagnetic substances have a strong magnetic ordering due to parallel alignment of spins, while antiferromagnetic substances have antiparallel alignment.

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