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Which of the following statements is/are true?

A. If we decrease temperature and increase pressure, we can liquefy atmospheric gases.

B. A hot dry day means the temperature of the atmosphere is high and the humidity of air is low, Both these factors increase the rate of evaporation and thus enormous cooling is produced.
1. 1 only
2. 2 only
3. Both 1 and 2
4. Neither 1 nor 2

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Correct Answer - Option 3 : Both 1 and 2

The correct answer is Both 1 and 2.

  • The gases can be converted into liquids by bringing its particles closer, so atmospheric gases can be liquefied either by decreasing temperature or by increasing pressure. Hence, statement 1 is correct.
  • On a hot dry day, the temperature is high and humidity is less which helps in better evaporation.
  • Due to the higher rate of evaporation, it gives better cooling effect. Hence, statement 2 is correct.
  • That is why a desert cooler cools better on a hot dry day.

  • Humidity tells you the moisture content of the atmosphere, or how much water vapor there is in the air. 
  • When the humidity is high it feels oppressive outside because sweat doesn't evaporate and provide cooling. 
  • When the humidity is low, you feel cooler but your skin dries out and you get dehydrated more easily because more moisture is being evaporated from your body.

  • Desert Cooler - 
    • In a desert cooler, the water inside it is made to evaporate.
    • This leads to the absorption of energy from the surroundings, thereby cooling the surroundings.
    • Evaporation depends on the amount of water vapour present in the air (humidity).
    • If the amount of water vapour present in the air is less, then evaporation is more.
    • On a hot dry day, the amount of water vapour present in the air is less.
    • Thus, water present inside the desert cooler evaporates more, thereby cooling the surroundings more. 

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