Why do liquids exert vapor pressure?Does this vapor pressure exist at all temperature?Why?

Answer 1

I'll explain it simply. The atoms or molecules in the liquid are moving around. At the surface of the liquid, some of these atoms bounce right out into the air (or whatever is there). The vapor pressure is basically the amount of molecules or atoms of the liquid that can bounce out; that is, the more atoms/molecules in the gas state, the higher the pressure.

More atoms can bounce out of the liquid when the temperature is higher, because there is more energy of motion available. If temperature is raised high enough, all of the atoms bounce out, and this is what happens when the liquid boils. The atoms or molecules are moving so much they can't stay close enough together to stay as a liquid.

Answer 2

Vapor pressure is a result of the tendency to evaporate and condense, which all liquids do to some degree.

Vapor pressure is a function of temperature. That is, the higher the temperature, the higher the rate of evaporation, and thus the higher the vapor pressure. Since evaporation will always happen, vapor pressure will always be greater than zero, just really low at low temperatures.

Answer 3

1: Pressure means "force per unit area".
Vapor Pressure means the force per unit area exerted by vapors. The vapors posses this forces by the energy they have through the amount of kinetic energy they have from any (heat) source.
The sum total of the kinetic energy averaged over number of molecules of the liquid is called temperature.
If the temperature is higher, the kinetic energy is more and hence the force per unit area exerted by the vapors is higher, thus the pressure is higher.
2: Yes, vapor pressure exists at all temperatures, as explained above. At low temperature is may be negligible, but at higher temperatures it might be exploding.

Answer 4

LIQUIDS WHEN HEATED EXPAND CAUSING A RISE IN PRESSURE. WATER ALSO EXPANDS WHEN FROZEN WHICH WILL BREAK A CONTAINER IF IT IS COMPLETELY FULL AND CLOSED TIGHTLY.