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Q & A: Cooling sprays

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Most recent answer: 02/02/2012
Q:
how come air fresheners, hair sprays or any kind of aerosol feels cold when they are sprayed to skin?
- Mark L. Gesulga (age 21)
Tagum City, Davao Del Norte
A:
Hello Mark,

The cooling effect is mostly due to the compressed air in the aerosol container expanding in the environment. After exiting the nozzle, the compressed air expands and does work on the surroundings--thus losing energy. This then causes the temperature of the aerosol to decrease, causing it to feel cool on your skin.

Another possible explanation of the cooling effect could be evaporation. When aerosols are sprayed, they form tiny droplets of liquid in the air. When these tiny droplets of liquid come into contact with your skin, they can conduct thermal energy away from your skin. This causes the molecules in the liquid droplets to vibrate more quickly, and change from a liquid phase into a gaseous phase. This process is known as evaporation.

In addition, because the tiny droplets of liquid have such a high surface area to volume ratio, the molecules within the tiny droplets can turn into a gaseous phase even more quickly (as compared to bigger droplets of liquids). This means that a fine mist of liquid sprayed onto your skin may feel cooler as compared to if you poured the same amount of liquid onto your skin.


Maurice

(published on 02/02/2012)

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