Define the following.
Chemical change

Explanation

**Step-by-Step Text Solution:**

1. **Definition of Chemical Change:**
A chemical change is a process where one or more substances (reactants) are transformed into different substances (products) with distinct properties.

2. **Irreversibility:**
Chemical changes are generally irreversible. This means that once the reactants have been converted into products, they cannot be easily reverted back to their original form. For example, when sodium reacts with oxygen to form sodium oxide (Na2O), the sodium oxide cannot be converted back into sodium and oxygen under normal conditions.

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