• Anything that possesses mass, occupies space, offers resistance and can be perceived through one or more of our sense is called matter.

Matter is made up of particles. Particles of matter have space between them and are continuously moving and attract each other.

Matter can exist in three states-

  1. Solid
  2. Liquid
  3. Gas.
  4. Solid has a definite shape, distinct boundaries and fixed volumes, Solids have a tendency to maintain their shape when subjected to outside force. Solids may break under force but it is difficult to change their shape, so they are rigid.
  • Liquids have no fixed shape but have a fixed volume. They take up the shape of the container in which they are kept. Liquids flow and change shape, so they are not rigid but can be called fluid.

A gas has no definite volume or shape. Gases are highly compressible as compared to solids and liquids. The liquefied petroleum gas (LPG) cylinder that we get in our home for cooking or the oxygen supplied to hospitals in cylinders is compressed gas. Compressed nature gas (CNG) is used as fuel these days in vehicles.

The forces of attraction between the particles (inter-molecular force) are maximum in solids, intermediate in liquids and minimum in solids, intermediate in liquids and minimum in gases. The spaces in between the constituent particles and kinetic energy of the particles are minimum in the case of solids, intermediate in liquids and maximum in gases.

  • The arrangement of particles is most ordered in the case of solids, in the case of liquids layers of particles can slip and slide over each other while for gases, there is no order, particles just move about randomly.

In spite of above differences all kinds of matter have a common property, the property of having a mass.

The states of matter are inter-convertible. The state of matter can be changed by changing temperature or pressure.

  • On increasing the temperature of solids, the kinetic energy of the particles increases. Due to the increase in kinetic energy, the particle start vibrating with greater speed. The energy supplied by heat overcomes the forces of attraction between the particles. The particles leave their fixed positions and start moving more freely. A stage is reached when the solid melts and is converted to a liquid. The temperature at which a solid melts to become a liquid at the atmospheric pressure is called its melting point.

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