Effect of Temperature in The Change of State of Matters PDF
Effect of Temperature in The Change of State of Matters PDF
Effect of Temperature in The Change of State of Matters PDF
Change of state of matter: A substance may exist in three states of matter i.e., solid, liquid
or gas, depending upon the conditions of temperature and pressure. By changing the conditions
of temperature and pressure, all three states could be obtained (solid, liquid, gas). On heating,
solid changes into a liquid which on further heating changes into a gas.
Example-
Water exists in all three states.
Solid: Ice, Liquid: Water, Gas: Water Vapour.
Ice is a solid-state and may be melted to form water (liquid) which on further heating changes
into steam (gas). These changes can also be reversed on cooling.
It is observed that the temperature of the system does not change after melting point is
achieved until all the ice melts, though we continue to heat the beaker. This is happening
because the heat supplied is used up in changing the state by breaking the intermolecular forces
of attraction which holds them in the solid state. As a result, there is no change in temperature
until all the ice melts. This energy required to change a solid int o liquid is called "latent
heat". The word "latent" means "hidden" because this energy is hidden into the contents of
the beaker.
Latent heat is of two types:
(a) Latent heat of fusion.
(b) Latent heat of vaporization.
(b) Latent heat of vaporization: The latent heat of vaporization of a liquid is the quantity of
heat in joules required to convert 1 kilogram of the liquid (at its boiling point) to vapour or gas,
without any change in temperature. The latent heat of vaporization of water is 22.5 ×
105 joules per kilogram (or 22.5 × 10 5 J/kg).
The boiling point of a liquid also indicates the strength of the inter -molecular force
of attraction between particles. Volatile liquids such as alcohol, petrol, and
acetone have very weak intermolecular forces. Therefore, they boil at a low
temperature. On the other hand, water has stronger inter -molecular forces of
attraction and therefore, it boils at a higher temperature. When steam is cooled, it
condenses to water & when water is cooled, it changes to ice.
Note: The numerical value of boiling point and liquefaction point is same.
For example, if the boiling point of water is 100°C (373 K), then the liquefaction point of steam
is 100°C (373 K).
Condensation is opposite to evaporation and freezing is opposite of melting.
Sublimation:
Sublime: A gaseous form, directly formed from a solid on heating, is known as sublime.
Sublimate: A solid state of matter formed directly from its gaseous state on cooling is called
sublimate.