Define the following.
Physical change

Explanation

### Step-by-Step Solution

1. **Definition of Physical Change**: A physical change is a type of change that affects one or more physical properties of a substance without altering its chemical composition.

2. **Reversible Nature**: Physical changes are generally reversible. This means that the substance can return to its original state after the change has occurred. For example, when water (H2O) is heated, it can change from a liquid to a gas (steam). When cooled, the gas can condense back into liquid water.

3. **Example of Physical Change**: A common example of a physical change is the transition of water from liquid to gas (vaporization) and back from gas to liquid (condensation). In both cases, the chemical composition of water (H2O) remains unchanged.

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