Chapter 1 Matter in Our Surroundings

This chapter explains about how a small particle constitue to form matter into different forms like solid, liquid and gases. Matter is that substance that occupies space have mass and volume. Various forms of matter exhibit different properties how the particle are interacted. Lets read more about matter.

Download pdf of NCERT Solutions for Class Science Chapter 1 Matter in Our Surroundings

Download pdf of NCERT Examplar with Solutions for Class Science Chapter 1 Matter in Our Surroundings

Exercise 1

Exercise 2

  • Q1 The mass per unit volume of a substance is called density. (density = mass/volume). Arrange the following in order of increasing density – air, exhaust from chimneys, honey, water, chalk, cotton and iron.

    density = mass / volumes

    Arranging substance in their increasing order of densities

    Air < exhaust from chimneys < cotton < water < honey < chalk < iron.

    Reason: (The most heavy will be the highest density.) Iron is heavy so there is more density and the air is light so its density is low. 

    Density is a property of matter which tells about how tightly particles are packed in a given object.

    Q2 (a) Tabulate the differences in the characterisitcs of states of matter. (b) Comment upon the following: rigidity, compressibility, fluidity, filling a gas container, shape, kinetic energy and density.

    (a) Solid:

     * Particles are rigid and un-incompressible.
     * Particles possess a definite shape and volume.
     * Particles don't have the ability to flow.
     * Particles have the least kinetic energy.
     * Particles have high density. eg.: salt, iron, gold, chalk.


     * Particles are not rigid but can be compressed to a limited extent.
     * Particles have only a definite volume but acquire the shape of a container in which they are kept.
     * Particles can easily flow from higher to the lower level.
     * Particles have more kinetic energy than solid.
     * Particles have less density than solids. eg.: water, alcohol, petrol etc.


     * Particles are not rigid and can be compressed easily.
     * Particles don't have a definite shape of volume.
     * Particles can flow in all the possible directions.
     * Particles have maximum kinetic energy.
     * Particles have the least density. eg.: air, CNG, smoke etc.


     * Rigidity: It is the property of matter to maintain its shape even if an external force is applied and the solids show it this property.

     * Compressibility: It is the property of matter to allow decrease in volume under high pressure and gases show this property.

     * Fluidity: It is the property of a substance to easily flow and allow change in its shape under external forces and this property is shown by both liquids and gases.

     * Filling a gas container: Gases can be compressed easily hence they can be filled within a vessel at high pressure. This property of gases allows their convenient filling into a small container or cylinder and that also in a large volume. It also allows their easy transport from one place to other e.g. CNG.

     * Shape: According to the type of matter shape differ depending upon the location of particles like solid have a definite shape while liquid acquire the shape of their container and gases as such don't have any shape.

     * Kinetic energy: It is the kind of energy present in an object when it is under motion as the particles of that object are continuously moving therefore the object has kinetic energy. However, greater is the movement, more will be the kinetic energy and vise-versa.

    Kinetic Energy = Gas > Liquid > Solid

    Kinetic energy of gas is maximum.

     * Density: Mass per unit volume of a substance is known as its density.

    Density = Solid > Liquid > Gas

    Solids have the greatest density.

    Q3 Give reasons (a) A gas fills completely the vessel in which it is kept. (b) A gas exerts pressure on the walls of the container. (c) A wooden table should be called a solid. (d) We can easily move our hand in air but to do the same through a solid block of wood we need a karate expert.

    (a) Since the attraction force between particles of a gas in negligible i.e., that is extremely less hence particles freely move in all possible directions as a result gas fills completely the vessel in which it is kept.

    (b) Freely moving particles of gas hit the walls of its container continuously and randomly therefore such random and erratic motion of gas particles exerts pressure on the walls of the container.

    (c) A wooden table should be a solid because the particles of wooden table are quite rigid, have a fixed location and also possess a definite shape and volume. Due to all these properties we should call a wooden table a solid substance.

    (d) Air is a mixture of gases and since particles of gal are far apart so the name is true for air therefore we can easily move our hand in air. But a solid block of wood is hard and rigid that resists any change in location of its particles hence we need a karate expert in case of a solid block of wood.

    Q4 Liquids generally have lower density as compared to solids. But you must have observed that ice floats on water. Find out why.

    When water freezes to form ice, some empty spaces are created. As a result, volume increased for the same mass of water. In some words, mass per unit, volume or density of ice is lower than that of water and hence ice floats on water. (The density of water is maximum at 4.C.)

Exercise 3

Exercise 4

Exercise 5

Popular Questions of Class 9 Science