how does boiling of a liquid different from its evaporation?

Answer 1

boiling
- happens at a particular temperature which is 100 degrees
- happens throughout the whole liquid

evaporation
- happens at any wam temperature
- happens only on the surface

Answer 2

Evaporation can occur below boiling point. Probably the best known example is wet laundry hanging on a line: the temperature never rises to 100°C (and air pressure is assumed to be normal all the time), but still the water in the laundry evaporates, carried off as air humidity. This process will take up heat.

A boiling liquid has steam and liquid in equilibrium. Any heat you add will evaporate some of the liquid, any heat you take out will cause some of the steam to condensate.

Answer 3

Boiling is a form of evaporation but evaporation is not necessarily a form of boiling. Boiling occurs when evaporation forms bubbles within the liquid. Bubbles may form for example at the bottom on a pot on a stove when the water is heated enough locally to increase water vapor pressure to greater than the static pressure (weight) of the liquid. Water under pressure (in a pressure cooker?) may boil throughout the liquid if the pressure is suddenly reduced (take off the cover?). The liquid also 'flashes' to steam.

Evaporation is a process where energy within the liquid can break the attractive bonds (surface tension) of single water molecules at the surface allowing them to separate and enter the atmosphere. At the same time water molecules may reenter the liquid. Evaporation is a net loss of water molecules. At 100% relative humidity in a room, as many water molecule evaporate as are returned to the liquid (or damp cloth?) and drying is not possible.

Answer 4

Evaporation is a characteristic of phase equilibrium. Any liquid in a closed system will evaporate until the pressure exerted by it's vapor plus atmospheric pressure is equal to the partial pressure exerted by the liquid, which is a function of temperature. If you were to close off a glass of water, for instance, some of the water would evaporate, but it would eventually reach equilibrium and no net evaporation would then occur. However, since most sources of water, such as a puddle, are not closed, they continue to equilibrating until there is no water left.

The boiling of a liquid is also related to the partial pressure exerted by the species, but it is what occurs when the partial pressure exerted by the liquid is equal to the pressure on the liquid. At this point, the liquid will continue to vaporize as long as heat is added. At most pressures (~1 atm) water boils at 100 degrees Celsius, but at lower atmospheric pressures, it boils at a lower temperature, which is why you have to use a pressure cooker if you go camping in the mountains.

Answer 5

Liquids have a critical temperature where they boil - i.e. go from a liquid phase to a gaseous phase. For example, water has a boiling point of 100°C, where is changes into a gaseous phase. Evaporation is part of the water cycle, and depends on the surroundings, but it has no critical temperature, it occurs if it is 10°C or 40°C.

Answer 6

Evaporation can take place at any temperature.

Vaporisation only takes place at the boiling point of a liquid as long as heat is continued to be added.

Liquids at any temperature have a vapour pressure. This means that due to molecular activity, a number of molecules are constantly escaping from the liquid.

Consider a puddle of rain water on a cloudy day. If no further rain comes along, the puddle will gradually dry up and, the breezier it is, the faster it will take place.

Boiling on the other hand, is raising the temperature (Sensible Heat) of a liquid to its vaporisation point (as in water at 100 °C) the water due to addition of more heat, (Latent Heat) is vaporising to steam.

(Note: If the person going crazy with the 'thumbs down' know any better, write your piece and let us all read it).

Answer 7

when you boil a liquid, it does not mean that you are evaporating it. When the liquid (e.g: water) is boiled till its boiling point (100 celsius), its particle starts to vibrate more.
However, when you are evaporating the liquid, you are changing its state into a gaseous state. In this process, the particles are able to move anywhere and at greater speed.

Answer 8

Boiling is occuring all through the liquid.
Evaporation occurs only on the surace