what is latent heat of vapourisation and is it a type of vapour pressure.?

Answer 1

Latent heat of vaporisation is the heat that is absorbed AT CONSTANT TEMPERATURE during phase transformation of a liquid into a gas. Vapour pressure, on the other hand is the pressure above a liquid surface when the liquid and its vapours are in equilibrium with each other.

Answer 2

Latent heat simply means hidden heat, because during melting or boiling, the temperature remains constant. So, the heat is hidden as potential energy and is due to a change of state and the resulting change in the bonds. For example solids have stronger bonds than liquids and liquids have stronger molecular bonds than gases. Thus it needs some energy (provided by heat) to break the bonds which is what a change of state like melting of ice and boiling of water means.

Vaporisation is a process of slow change of molecules from a liquid state to a gaseous state at room temperature. A few molecules of the liquid attain a kinetic energy high enough for the molecules to break free of the liquid vapor interface. Similarly a few molecules do get kicked back into the liquid from the vapor. An equilibrium is set up, esp. if the top of the vessel containing the liquid is closed so that the vapor cannot escape. If the vessel is open, vapor escapes and evaporation continues and the heat needed is drawn from the liquid itself, thus cooling it. The sense of cooling which you experience when alcohol or acetone is rubbed on your skin is due to the evaporative cooling - the heat of vaporisation is drawn from the body. Desert coolers (also called swamp coolers) also works by the evaporative cooling of water accelerated by a fan blowing across. When you wash your face and come out into breeze or under a fan, you feel cool again because of the evaporation of water.

Vapor is different from a gas only in the sense that it is wet, i.e.in contact with its liquid. So, vapors don't obey gas laws.

Vapor pressure is dependent on the temperature and at the boiling point, equal the atmospheric pressure at that place.

Hope things are a little clearer now.

Answer 3

There are two latent heats associated with water. First, solid ice consists of a mass of interlocking chains of water molecules (that use space less efficiently than water, are less dense and float). As heat is gradually added the molecular chains are broken and the ice becomes liquid (a change of state). The heat added is called the latent (hidden) heat of fusion because it is added with no temperature increase until the last chain is broken. If the ice water is heated, the water molecules vibrate more and more storing heat. Some of the molecules have enough instantaneous energy (above average from collisions) to escape the liquid surface (escaping surface tension) to become a vapor. Vapor pressure can exist at room temperature (for example under the lid of a jar of canned tomatoes). When the liquid temperature is increases such that vapor pressure equals atmospheric pressure the water will boil producing steam (another change of state). As long as the liquid remains unconfined, it will turn to steam expanding to vapor at atmospheric pressure. The heat added to change liquid to vapor is called the latent (hidden) heat of vaporization because there is no temperature increase until all liquid is steam. Adding more heat to the vapor produces superheated steam. If water is turned to vapor in a confined vessel (boiler) the pressure will depend on the temperature of the liquid and vapor in the boiler. Vaporization within a confined vessel produces a vapor pressure because of the collected kinetic energy (motion) of the water molecules colliding with the boiler shell.

Answer 4

The latent heat of vaporization is the amount of heat needed to cause a material to boil, or change from a liquid to a gas. The temperature stays the same during this process.

Answer 5

Latent heat of vaporization is NOT vapor pressure. For example, when you heat a quantity of water, it will increase in temperature according to its specific heat, 4.184 J/g*deg C, until it reaches its boiling point. When the sample reaches 100 deg C, the boiling point of water, it doesn't magically and instantly become steam (gaseous water). If you want to convert all the liquid water to steam, you must *keep heating the sample*. At this point, the temperature of the liquid water does not change with added heat. Instead, the sample uses that heat to undergo a phase transition from liquid to gas. The amount of heat a substance requires to effect this phase transition while maintained at its boiling temperature is called its "latent heat of vaporization." In water's case, this value is quite high at 2258 J/g.

Answer 6

There is one thing missing ,When the liquid changes to steam something special happens. Even if the heat is continued the water does not increase because each CC of water that is converted to steam there is 60 calories absorbed.
That is where the monster comes from in a storm ,when it condenses u get 60 calories of heat that creates a chimney of heat that causes the up draft which can turn into a tornado.