Why do alkenes show addition reactions?

Explanation

### Step-by-Step Solution:

1. **Understanding Alkenes**: Alkenes are hydrocarbons that contain at least one carbon-carbon double bond (C=C). This double bond is a key feature that distinguishes alkenes from alkanes, which only contain single bonds.

2. **Unsaturation in Alkenes**: Alkenes are classified as unsaturated hydrocarbons because they do not contain the maximum number of hydrogen atoms that can be bonded to the carbon skeleton. For example, ethene (C2H4) has two fewer hydrogen atoms than ethane (C2H6), which is saturated.

3. **Reactivity of the Double Bond**: The presence of the double bond in alkenes makes them more reactive than alkanes. The double bond consists of one sigma (σ) bond and one pi (π) bond. The π bond is relatively weak and can be broken easily during chemical reactions.

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