Why is the spray from aerosols cold?

Question

Why is the spray from aerosols cold?

Answer 1

It's not really - just anything below body temperature feels cold.

That's why you have showers at around 37 - 38 degrees celsius.

Here's the sciency bit: when something colder than you touches your skin, the two substances must reach equalibrium (or is it equilibribrium?) (I assume you know that just means they must be the same) so the material saps some of the heat from you. Metal is a good conductor of heat which is why it often feels colder than other things; it takes the heat faster.

Interestingly, cold water from the tap is around room temperature and hot water is forty degrees, only two to three degrees hotter than your body.

Sorry if I've got this completely wrong!

Answer 2

because germs cannot survive in a freezing environment. just like sometimes they can't survive in a scolding one.

Answer 3

Most modern aerosols use a liquefied gas as the propellant. The gas has been turned into a liquid by putting it under pressure. When the pressure is released it returns to a gas, the energy it uses to change from a liquid to a gas is the heat surrounding it, so thats why it feels cold.

Answer 4

Expansional cooling.

Answer 5

The liquid is compressed and is at the same temperature as the outside. When you spray it, the spray is no longer compressed so the pressure decreases, causing the temperature to be lower- Boyles Law

Answer 6

Usually propane or butane are used as propellants in aerosols. When the product leaves the aerosol nozzle, it's pressure immediately drops, thus lowering the boiling point of the product. If it's propane, (boiling point of -42 deg at atmos pressure) then it is immediately exposed to a temperature way above it's boiling point, and it will boil, vapourising instantly. It will cool to it's natural boiling point for that specific pressure, ie -42 deg.

As a few others have said, expansion causes cooling. Joules thomson effect of lowering pressure.

Answer 7

This is based on the Ideal gas law:

PV=nRT

As you spray the aerosol the pressure, P, of the can is decreasing.  Therefore the temperature of the can (and the spray) has to decrease to fulfill the equation.