Here's why:

* Thermal Expansion: Liquids, like water, expand when heated. This means that the volume of the water will increase as its temperature rises.

* Density Changes: As water expands, its density decreases. Density is mass per unit volume, so a decrease in density means the same mass of water occupies a larger volume.

Therefore, 1 liter of water at 80 degrees C will have a slightly larger volume than 1 liter of water at a lower temperature, like 4 degrees C (where water has its maximum density). The exact volume increase will depend on the initial volume and the temperature change.

However, the difference in volume is usually small and often negligible for practical purposes.