when you dip your finger in water, when you blow on it, why does it feel cold when your breath is at room temp

Question

just curious.

many thanx.

Answer 1

Because water evaporates and evaporating water takes away energy i.e. temperature from your skin and you feel cold that is fall in temperature.

Answer 2

The previous answers are correct in some ways, but do not give the full reasons for why you finger feels cold. It is actually much nore complex. I will try to explain in simple terms.
Any matter is composed of atoms, either individually or as compounds of different kinds of atoms joined together to form molecules. In a pure element, all the atoms are the same. In a compound such as water, there are different kinds of atoms. Water contains hydrogen and oxygen atoms, in the well known form of two hydrogen atoms and one oxygen atom joined together to form one molecule. All atoms or molecules posses energy, and the more energy they possess, the higher the temperature of the body being measured or sensed. If we consider the film of water on your finger, it contains many millions of molecules, each conaining a very small amount of energy, in the form of kinetic energy due to their motion. The molecules are actually whizzing about within the film of water. It is also the case that the molecules do not all have the same amount of energy. Some have more than others. The temperature that we measure actually represents the AVERAGE ENERGY of ALL the molecules. Water also has a property called SURFACE TENSION. This is because the molecules at the surface are actually joined together more strongly than those below the surface. When you blow on your wet finger, the surface tension is reduced, and some of the molecules are able to break away from the rest and float off into the air. This is commonly known as evaporation. The point that is missed by the other answers is that the molecules that are able to escape the surface temsion are those with the highest energy, i.e the ones that are moving about at the highest speed. The result of this is that for the molecules remaining on your finger, the AVERAGE ENERGY is less than it was before, so therefore the temperature of the water is reduced, and hey presto, your finger feels cooler than before. This also explains why you feel cold when you get out of the swimming pool or sea when it is windy, except in this case it is all over your body.
I hope that you can understand this explanation. It is really all about energy of atoms / molecules

Answer 3

This is more of a physics question.

Water is a substance having a high latent heat of vaporisation. This means that to evaporate a small amount of water, you have to supply it with a lot of energy. Therefore, as it evaporates from your finger, it is actually using the heat energy of your body through your finger. When water evaporates, molecules of water vapour accumulate just above the area where water is evaporating. This reduces the evaporating capacity of the water as more and more water vapour molecules accumulate and there won't be enough space for new water vapour molecules. However, when you blow on your finger, you are actually pushing away the accumulated water molecules away from the area near your finger.

Therefore, you facilitate the evaporation process by creating space for all the water to evaporate. The temperature of your breath hence doesn't matter here.

Also, you notice the cold feeling more so because you are accelerating the evaporation process.

Hope it helps

Answer 4

The water does evaporate and with it take away heat energy. Also, your body only registers differences in heat. The water will have made your finger cold, so when you blow on it (with breath which is warmer), your skin will register the difference.

Answer 5

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Answer 6

Your breath is vaporising the water from your finger.
Vaporisation requires heat energy called 'Latent Heat of Vaporisation'.
The heat required is removed from the skin of the finger as 'Sensible Heat of Cooling'. This causes cooling of the skin.

(The same process takes place when you are hot and sweaty. When you've been working hard ouside, you sweat. When you stop working, you start to feel cold as the sweat is evaporating from your skin).

Answer 7

when heat is absorbed, water molecules evaporates. However the temperature is still trapped near the skin.

When blown, these molecules, together with the heat that they have absorbed, moves away from the skin surface and hence it feels cold.

Answer 8

Blowing causes the water to evaporate which draws heat out of your body making you feel cooler.
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Answer 9

Because water takes heat from the body to evaporate as such you feel cold,air also helps in evaporation.

Answer 10

Because your finger is likely not at room temperature. Its usually when you put your finger in warm or hot water.