Matter in our Surroundings Notes of Science Class 9th | PDF Download

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1.4- Properties of matter

Although the above shown characteristics of matter can also be referred to as different properties of that type of matter, matter possess some other different properties too which are used to identify between different types of matter.

1.4.1-Kinetic energy

The molecules of different matter move with the help of kinetic energy possessed by them. Kinetic energy varies in solids, liquids and gases.In solids, kinetic energy is the least, i.e. molecules of solids doesn’t show any movement. In liquids, it is higher than the solids but less than that of gases, that’s why molecules of liquid show a lot of movement i.e. they flow. In gases, kinetic energy is the highest. That’s why the molecules of gases are able to move at high speed.

1.4.2-Force of attraction

The force of attraction is the force possessed by the molecules of different types of matter that attracts other molecules towards them. This force makes the molecules of different matter to have little or more space between them. The more force of attraction a substance have, the less molecular space it has. Basically, molecules of solids have the highest force of attraction because they are closely attached to one-another.

Liquids have less force of attraction between its molecules. That’s why the molecules of liquid have more molecular space than the solids. Finally, the gases have the least force of attraction between its molecules. That’s why one molecule of a gas is far away from another molecule of the same gas.


The intermixing of different particles of matter on their own is known as diffusion. For example: – The oxygen present in the air diffuses with water in the seas, oceans,lakes, etc. This oxygen is utilized by various sea creatures which take this oxygen for respiration and various other processes. This is how the aquatic animals get oxygen.

Rate of diffusion differs in various types of matter. As you can see above, solids have least rate of diffusion, liquids have medium, and gases have highest rate of diffusion.

1.5-The effect of temperature on these properties

Temperature has different effects on the kinetic energy, force of attraction and diffusion of matter. We will look at these effects one by one on various forms of matter.

  • But first, what happens on heating something, say water? The water takes the form of vapors, which is the gaseous form of H2 These vapors have more kinetic energy than the liquid form of water.Also, when water in the solid form, i.e. ice is heated, it turns to liquid form possessing more kinetic energy than ice.So we can see that on heating, kinetic energy of a substance increases while on cooling, the kinetic energy of same substance will decrease. This means that kinetic energy of a substance increases with the temperature.
  • Again, the molecules of ice have greater force of attraction. But on heating, ice turns into water and force of attraction decreases. On heating this water again, it turns into vapors , which reduces the force of attraction to the least. So, we can say that the force of attraction reduces as the temperature is increased.
  • In case of diffusion, we can see that diffusion mainly occurs between liquids and gases, and is least in the solids. So, any solid needs to be converted into liquid or gas in order to increase the rate of diffusion. This means that rate of diffusion increases with the increase in temperature.

What happens when hot cooked food is kept open in the kitchen? The smell of the food reaches you. This happens because the particles of aroma of food mix with the particles in air and reach you.

Actually, due to high speed of particles and large space between them, gases can diffuse faster into other gases as compared with other forms of matter.

Matter in our Surroundings Notes of Science Class 9th | PDF Download

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