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[Page 1] Some Basic Concepts of Chemistry Changes Among Various States of Matter Change of State - An Overview In daily life, we see different kinds of changes in the states of matter. The formation of ice cubes from water in the refrigerator is an example of a change in the state of matter from liquid to solid. When water is boiled, vapours are formed. This is an example of change in the state of matter from liquid to gas. The following terminologies are used to describe the changes in the states of matter. • Chan ge from the solid state to the liquid state is called melting . • Change from the liquid state to the solid state is called freezing . • Change from the liquid state to the gaseous state is called vapourisation . • Change from the gaseous state to the liquid state is called condensation . There are two other changes between the three states of matter — sublimation and deposition. Sublimation : It is the process in which a substance changes directly from the solid state to the gaseous state without entering into the liqu id state. The changing of snow into water vapour is an example of sublimation. Some common examples of substances that sublime are dry ice, camphor, and naphthalene. Deposition : It is the process opposite to sublimation. In this, a substance changes direct ly from the gaseous state to the solid state. Frost is an example of deposition. Did You Know? When we open the refrigerator, we see freezing fog. This is nothing but condensed water. Air contains vapours. When we open the refrigerator, the temperature comes down. This condenses the vapours into tiny drops of water and produces freezing fog. Temperature Affecting the Change of State Let us perform an activity to understand the effect of temperature on the different states of matter. Procedur e : Take about 150 g of ice in a beaker and use a laboratory thermometer to note the temperature of ice. Start heating the beaker on a low flame and record the temperature when the ice starts melting. Observe the temperature when all the ice gets converted into water. Stir the water with a glass rod till it starts boiling. [Page 2] Result : In the beginning, the temperature of ice is below 0°C. When ice begins melting, the temperature is recorded to be 0°C. Temperature remains constant at 0°C untill all the ice melts. The continued heating of water causes its temperature to rise. Conclusion : It can be concluded from this activity that an increase in temperature changes a substance from its solid state to its liquid state, and further heating (i.e., further incre ase in temperature) changes the liquid so formed into vapour. Temperature Affecting the Change of State You know that matter, irrespective of its state, consists of particles. What happens to these particles of matter while it is undergoing a change in i ts state? For us to understand