Why are aerated water bottles kept under water during summer ?

Explanation

### Step-by-Step Solution:

1. **Understanding Aerated Water Bottles**: Aerated water bottles contain carbon dioxide (CO2) dissolved in water under pressure. The CO2 is added to the water to create carbonation, which gives the drink its fizzy quality.

2. **Effect of Temperature on Solubility**: The solubility of gases in liquids decreases as the temperature increases. This means that during summer, when temperatures rise, the amount of CO2 that can remain dissolved in the water decreases.

3. **Increased Gas Above the Liquid**: As the temperature rises and the solubility of CO2 decreases, more CO2 will be present in the gaseous state above the liquid surface in the bottle. This can lead to an increase in pressure inside the bottle.

...