How Evaporation Causes Cooling
When water evaporates, it needs heat energy to change from liquid to gas. It takes this heat from its surroundings or the surface it is on. As a result, the surface loses heat and becomes cooler.
The Earthen Pot (Matka/Surahi)
In summer, people store water in clay pots (Matka or Surahi) to keep it cool.
- Mechanism: Earthen pots have tiny pores (holes) in their walls.
- Process: Water slowly seeps out through these pores to the outer surface.
- Cooling: This water evaporates using heat from the water inside the pot and the surrounding air. By taking heat away, the remaining water inside the pot cools down.
Other Examples
- Sweating: Our body produces sweat. When sweat evaporates, it takes heat from our skin, making us feel cool.
- Hand Sanitiser: When you rub alcohol-based sanitiser, it evaporates very quickly, absorbing heat from your hand, leaving it feeling cold.
- Sprinkling Water: In summer, people sprinkle water on roofs or the ground. The evaporation of this water absorbs large amounts of heat, cooling the area.
Tip
Activity Idea: The Pot-in-Pot Cooler. You can create a simple cooler by placing a small pot inside a large pot, filling the gap with wet sand, and covering it with a wet cloth. The evaporation from the wet sand keeps the inner pot very cold, preserving vegetables!