# Interconversion of States of Matter

#### Summary

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Matter can change from one form to other form i.e from solids to liquids to gases.
The phenomenon of the change of matter from one state to another and back to original state is known as interconversion of the sates of matter.
Matter can be changed from one state to another by changing temperature or pressure.

Change in state of water
When heat energy is supplied to ice it changes into water and then to vapor. If we cool the steam it gets converted into water and further cooling of water changes into ice.
Here the heat energy is used up in changing the state of matter. the heat is used to increase the kinetic energy of the particles of ice to such an extent that they break away from the rigid lattice structure of the solid form, ice, and move around freely to form the liquid form, water. So, until all the ice has melted, the heat absorbed does not raise the temperature of the ice-water mixture. In the same way the temperature does not change while a liquid is boiling. This heat, which does not raise the temperature of the body, is called Latent Heat.

Melting or Fusion
Melting is the process where solid changes into a liquid at a particular temperature.

Melting point
The temperature at which a solid melts to become a liquid at the atmospheric pressure is called its melting point.

Melting points of some solids

 Solids Melting point Ice (H2O) 00C Sodium chloride (NaCl) 8000C Iron 15350C

Latent heat
The word 'latent' means hidden. The characteristic amount of energy absorbed or released by a substance during a change in its physical state that occurs without changing its temperature is known as latent heat.

Latent heat of fusion
Latent heat of fusion is the amount of heat energy required to change 1 kg of a solid into liquid at atmospheric pressure at its melting point.

Boiling
Boiling is the process where a liquid  changes into a vapor at a particular temperature.

Boiling point
Water boils at 1000C. At that temperature, it changes from the liquid state to the gaseous state. The temperature at which a liquid starts boiling at the atmospheric pressure is known as its boiling point

Boiling points of some liquids

 Liquid Boiling point Water 1000C Chloroform 620C Sulphuric acid 2800C

Latent heat of vaporization
Latent heat of vaporization is the amount of heat energy required to change 1 kg of liquid into a gas at atmospheric pressure at the boiling point.

Freezing
The process, where a liquid converts into a solid, is called freezing or solidification.

On cooling a liquid the particles come closer due to the decreased kinetic energy.When the particles come closer the inter particular spaces are reduced and the forces of attractions  increased. Finally the particles are arranged themselves in a regular, compact manner.

Evaporation
The process where a liquid changes into vapor at any temperature below its boiling point is evaporation .Evaporation is a surface phenomenon. i.e evaporation takes place at the surface of the liquid.

Factors affecting evaporation

• Surface area
• Temperature
• Humidity and
• Wind speed.

Rate of evaporation - Surface area
The rate of evaporation increases with an increase of surface area. When the surface area is more, evaporation will be faster.

For example shallow quarries or bunds are built near the sea. The shallow bunds provide a relatively large surface area for water to evaporate quickly, Water from these bunds evaporates, leaving salt behind. Then the salt is collected and refined before use.

Rate of evaporation - Temperature
The rate of evaporation increases with an increase of temperature.
Cloths dry faster on a sunny day than on a cloudy day

Rate of evaporation - Effect of Humidity
The rate of evaporation increases with decrease in humidity.

Rate of evaporation - Effect of Wind
The rate of evaporation increases with an increase in wind speed.
The water vapor particles in atmosphere move away with the winds. This results in a decrease of the amount of water vapor in the surroundings. Due to this reason, clothes dry faster on a windy day than a normal day.

Evaporation cause cooling
During the process of evaporation, the particles of liquid absorb energy from the surroundings, to regain energy lost during evaporation. This absorption of energy from the surroundings makes the surroundings cold.

Differences between boiling and evaporation

 Boiling Evaporation It is a rapid process. It is a slow process. It is takes place at the entire mass of the liquid. It takes place at the surface of the liquid. It takes place at specific temperature called the boiling point of the liquid. It takes place at any temperature. The temperature of the liquid remains constant during boiling process. It causes cooling i.e the substance becomes cool due to evaporation.

Condensation
The process where vapor changes to a liquid is called condensation.
Example: The water vapor condenses and we receive the same water in the form of rain.
When you pour cold water in a glass. You will observe the formation of  water droplets on the outer surface of the glass . This is due to the condensation of water vapor present in atmosphere.

Sublimation
The process, where a solid, on heating, directly changes into gas without changing into liquid, and a gas, on cooling, directly changes to solid without changing into liquid is called sublimation.
Example: Solid ammonium chloride, on heating directly converts into vapors without changing to the liquid state. These vapors get condensed to the solid state by condensation process.
The sublimation of Naphthalene and camphor can take place without heating them. They sublimes at room temperature.

Difference between sublimation and vaporization
Vaporization is a transitional phase of matter from a solid or liquid phase to a gaseous phase.
For example: When heat energy is supplied to ice it changes into water and then to vapor.
Sublimation is a transitional phase of matter from a solid phase to gaseous phase without changing into a liquid phase.
For example: Solid ammonium chloride, on heating directly converts into vapors without changing to the liquid state.

Liquification process
A gas is liquefied by applying high pressure and reducing the temperature.
Example: petroleum gas is liquefied by applying high pressure and reducing the temperature to liquefied petroleum gas (LPG).
This principle is used in the liquification of air to separate the components of air.

#### Activities & Simulations

Activity 1
has created a wonderful animation on “Interconversion of States of Matter”. This animation explains the effect of changes of temperature and pressure on matter. From this activity students can also learn more about melting point, boiling point, evaporation, condensation, sublimation and more.
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Activity 2
Harcourtschool.com has created an educational based animation on “Evaporation and Condensation”. This animation explains the process of evaporation and condensation. And student can also learn about factors various effecting the evaporation process.
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Activity 3
Amrita.olabs.co.in has created an interactive activity on “Melting Point of Ice”. This activity explains how melting point of ice is recorded in the laboratory.
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Activity 4
Amrita.olabs.co.in has created an interactive activity on “Boiling Point of Water”. This activity explains how boiling point of water is determined in the laboratory.
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### 1 . Difference between solids,liquids and gases

Ans: Property Solids Liquids Gases

1. Kinetic energy
Very low (negligible) medium Very High
1. Rigid
...

### 2 . Define a) Rigidity b) Fluidity c)Fluid d) Compressibilty e) Shape

Rigidity: The property of solids being stiff and resist towards stress is called rigidity. In solids – Rigidity is very high. In liquids – l...