2. How are chemical changes different from physical changes?(2 points)

Chemical changes and physical changes differ primarily in the following ways:

1. **Formation of New Substances**: Chemical changes result in the formation of new substances with different properties, while physical changes do not create new substances; they only alter the state or appearance of the original material.

2. **Reversibility**: Physical changes are often reversible (e.g., melting and freezing of ice), while chemical changes are usually not reversible by simple physical means (e.g., rusting of iron cannot be undone easily).

Thus, the correct responses are:
- They form new substances.
- They are reversible (but note that while physical changes are often reversible, chemical changes are typically not).