Hinglish

Faster or Slower Evaporation

Class 6 Science · Chapter 8: A Journey through States of Water · NCERT Curiosity section 8.5

Learn

Gauri hangs out the washing. A spread-out bedsheet dries before a folded one, clothes dry faster in the sun than in the shade, faster on a windy day, and slower on a humid, cloudy day.

Evaporation is faster when there is: more surface area (spread out), more heat (sun, hot day), more wind (breeze, fan), and less water vapour already in the air (low humidity).

Salt is made this way along our coasts: seawater is let into shallow flat beds, where the sun and wind evaporate the water and leave the salt behind.

Explore: the drying race.

  1. Make the cloth dry as fast as possible.
  2. Now change ONLY the sun to shade. Does it take longer?

Remember

  • Evaporation is faster with more surface area, heat and wind, and lower humidity.
  • Change one factor at a time to test its effect (a fair test).

Quick check

Which wet cloth will dry first?

  1. Spread out in the sun on a windy day
  2. Folded in the shade
  3. Rolled up in a bag
  4. Spread out in a closed damp room
Answer

Spread out in the sun on a windy day. Large surface, heat and wind all speed up evaporation.

Think about it

Why does a plate of tea cool faster than a cup of the same tea?

One answer

In a plate the tea has a much bigger surface, so more of it evaporates at once, and evaporation takes heat away. The tea cools faster.

Practice

Practise with fresh questions at three levels (easy, medium, hard), some answered hands-on, with hints and worked answers. Get 4 of your last 5 right to finish the topic.