States of Matter - Matter in our Surrounding, Class 9, Science PDF Download

States of matter

Matter can be classified into 3 states on the basis of physical state-solids, liquids and gases.

Properties of solids:

(1) Solid state:

(a) A solid possesses a fixed volume and a definite shape, distinct boundaries and a definite mass.

(b) Solids are rigid and almost incompressible.

(c) Solids may break under force but it is difficult to change their shape.

(d) Solids generally possess high densities

(e) Solids do not exhibit diffusion.

(f) In solids, intermolecular forces of attraction are more strong.

Example: Table, chair, common salt, silver, ice, diamond, stone, sugar etc.

Example of solid state:

(i) A wooden block should be called a solid.

Explanation: A wooden block has a fixed shape and is rigid. Hence, it should be called solid.

(ii) A rubber band undergoes a change in shape on stretching, still, we call it a solid.

Explanation: A rubber band is called a solid because although it undergoes a change in shape on stretching yet it regains the same shape when the force is removed.

Solids generally do not exhibit diffusion: Due to smaller interparticle spaces and absence of translatory motion.

Some example in solids which show diffusion:

(a) If we write something with chalk on a blackboard and leave it as such for a few days, it becomes difficult to clean. This is due to diffusion of chalk particles into the surface of the blackboard.

(b) If two metal blocks are bound tightly together and left undisturbed for a long time, it is observed that some particles of one metal diffuse into the surface of the other metal.

(2) Liquid state:

Properties of Liquids:

(a) The matter in liquid state possesses a definite volume, a definite mass, but no definite shape.

(b) Liquids are also almost incompressible but are not rigid. In fact, they can flow from a higher to a lower level. Liquids have a property of fluidity and acquire the shape of the container in which they are kept.

(c) Liquids can undergo diffusion.

(d) Liquids also have high densities but less than that of solids.

(e) In liquids, Intermolecular forces of attraction are weaker than solid.

Examples: Water, alcohol, milk, diesel, petrol, kerosene oil, vegetable oil, fruit juices etc.

Solids, liquids as well as gases can diffuse into liquids This is due to the fact that the interparticle spaces in liquids are larger and the particles in liquid state move freely.

(3) Gaseous state:

Properties of Gases:

(a) The matter in gaseous state has neither definite volume nor definite shape but it has a definite mass. It acquires the shape and volume of the container.

(b) Gases are highly compressible.