Question

Describe the interconversion of three states of matter with the help of a diagram.

Accepted Answer

Matter exists in three different states, namely solid, liquid and gas. When we give heat to a body, it does not always increase the random motion of atoms and molecules thereby increasing the temperature of the body. Heat might change the arrangement of particles inside the substance, thereby changing the state of the body, with the temperature remaining constant. In other words, heat can change the state of a body, e.g., from solid to liquid or from liquid to gaseous. The process of change from one state to another at a constant temperature is called change of state. The following figure represents the interconversion of three states of matter.

When a solid is heated, it changes into its liquid at a fixed temperature. This process is called melting or fusion. The reverse happens when a liquid is cooled. The liquid freezes into solid at the same fixed temperature. This process is called freezing. For example, ice at $0 ° C$ on heating melts into water at $0 ° C$ , while water at $0 ° C$ on cooling freezes into ice at $0 ° C$ .

When a liquid is heated, it changes into its vapour (or gas) at a fixed temperature. This process is called vaporization or boiling. The reverse happens when vapour is cooled. The vapour condenses into a liquid at the same fixed temperature. This process is called condensation. For example, water at $100 ° C$ on heating vaporises into steam at $100 ° C$ , while steam at $100 ° C$ on cooling condenses into water at $100^{°} C$ .

When a solid on heating changes directly into vapour at a fixed temperature, the process is called sublimation. Similarly, the change directly from vapour to solid at a fixed temperature is called deposition. For example, camphor on heating changes directly into its gaseous state, while on cooling changes from its gaseous state to solid-state.

The change of state from liquid to gas at all temperatures is called evaporation. Thus, evaporation differs from boiling. Boiling is at a fixed temperature while evaporation takes place at all temperatures. For example, the drying of clothes is due to the evaporation of water. Evaporation is a slow process while boiling is a rapid process. Boiling takes place throughout the mass of the liquid whereas evaporation takes place at the surface of the liquid.

Describe the interconversion of three states of matter with the help of a diagram.

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