Matter in our Surroundings Class 9 Notes

Everything around us is made up of matter. Starting from the air we breathe to the plants and animals around us, everything is made up of matter. The chapter on Matter in our Surroundings is thus an important part of the CBSE class 9 science syllabus. Are you a student of the 9th standard struggling with this chapter? Worry not, in this blog we have some detailed matter in our surroundings class 9 notes that will help you in understanding the concepts easily. Take a look!

What is Matter?

Anything that occupies space, felt by senses and has mass is called matter. Matter was studied by Indian philosophers several centuries before and they classified matter into five elements, earth, air, sky, fire and water. Today, scientists have classified matter on the basis of the physical properties and chemical nature of matter. They are classified on the basis of:

• Particle arrangement
• Energy of particles
• Distance between particles.

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Physical Properties of Matter

In the matter in our surroundings class 9 chapter notes, we will be looking at the different characteristics of the particles of matter. Physical properties of matter refer to the properties that can be measured without any changes to their chemical nature. Examples are mass, volume, density, colour, boiling point, melting point and odour. The characteristics are as follows:

There is space between the particles of matter:

This can be proved with an experiment. Take water in a measuring cup. Mark the level of water. Add a teaspoon of sugar and stir. What happens to the sugar particles? They occupy the spaces between the particles of water. The water level does not change in the cup. The absence of change in the level of water proves that there is space between the particles.

The particles of matter are in constant motion:

This can also be proved with an experiment. Take a glass of water. Add a drop of ink into the water. The ink colour passes throughout the glass changing the colour of the water. This proves that the particles in matter are moving constantly. The spreading and mixing of one substance in another substance due to motion is called diffusion. Diffusion is the fastest in gases. It is a little slower in liquids and the slowest in solids. The diffusion is not the same in all gases. The more the density the slower is the diffusion.

The particles in matter attract each other:

There exists a force of attraction between the particles and it is called cohesion. It is the cohesion that holds the particles together to form matter. The force of attraction is not the same for all matters. It differs from one matter to another. For example, take an iron rod, an ice cube and a chalk piece. You can easily break the chalk into pieces with a hammer. It takes a little more force to break the ice cube and it is not possible to break the iron rod. This is because the force of attraction is very high in the iron rod.

Diffusion

As part of the matter in our surroundings class 9 notes, let us also look at the process of diffusion in detail. Diffusion refers to the process of mixing of different particles of substances. It occurs because of the movement of molecules in matter. It occurs in solids, liquids and gases.

• Diffusion in solids: It is slowest in solids because the particles in a solid don’t move. Example: Marks of a chalk left after wiping the blackboard.
• Diffusion in liquids: Diffusion in liquids is higher than solids but lower than gases. Example: Adding ink to water makes the whole solution blue due to the diffusion of liquids.
• Diffusion in gases: Diffusion is the highest in gases. Example: Smoke vanishes when it rises up in the air due to the diffusion of gases.

Must Read: Class 9 Atoms And Molecules Study Notes

States of Matter

We will be discussing the different states of matter in our matter in our surroundings class 9 notes. The five states of matter in our surroundings are:

• Solid
• Liquid
• Gas
• Plasma
• Bose-Einstein Condensate

In the matter in our surroundings class 9 chapter notes, we will also be looking at the different characteristic features of the states of matter in our surroundings:

Here is a table showing the properties of the three main states of matter:

Changes in the State of Matter in our Surroundings

As part of the matter in our surroundings class 9 chapter notes, we will be discussing how matter undergoes changes from one state into another. A solid can change into liquid on heating and similarly, liquid can change into gas on heating. In the reverse process, gas can change into liquid on cooling and liquid can change into a solid through the process of freezing.

Effects of Temperature on Matter

When thermal energy is added to states of matter there is an increase in temperature. This results in the change of the state of matter. Solid turns into a liquid which is called melting or gas which is called sublimation and liquids turn into a gas which is called vaporization.

The concepts discussed below as part of the matter in our surroundings class 9 chapter notes are very important for understanding the effects of temperature on changing the state of matter:

• Melting point – The temperature at which a substance changes from solid to liquid is called the melting point. The solid and liquid form of the matter exists in equilibrium at this point.
• Boiling point – The temperature at which a liquid changes into vapor is called the boiling point. The vapor pressure of the liquid is equal to the atmospheric pressure.
• Latent heat of fusion – The heat required to change 1 gram of a substance from solid to liquid state at its melting point without changing the temperature is called the latent heat of fusion.
• Latent heat of vaporization – The heat required to change 1 milliliter of a liquid into a gas at its boiling point without changing the temperature is called the latent heat of vaporization.
• Sublimation – The process through which a solid changes into a gas without passing through the liquid form is called sublimation. Sublimation is explained with a diagram below.

Effect of Pressure on Matter in our Surroundings

By applying pressure the distance between the molecules decreases. If the pressure is increased on liquids, it will become a solid. Similarly, if the pressure is decreased on a liquid it changes into gas.

Also Read: Circles Class 9 Study Notes

Evaporation

The process of changing of a liquid into vapour at a temperature below the boiling point is called evaporation.

In the matter in our surroundings class 9 chapter notes, we will be looking at the different factors that affect the process of evaporation. These are as follows:

• Temperature – The more the temperature the more is the evaporation
• Humidity – The more the humidity the lesser is the evaporation
• Wind speed – The more the wind speed the more is the evaporation
• Surface area – The more the surface area, the more is the evaporation

Must Read: Climate Class 9 – NCERT Study Notes

Important Questions on Matter in our Surroundings

In our matter in our surroundings class 9 chapter notes, we will also be providing some important questions that you can practice in order to get a high score in your exam. Here are some of the important questions:

• What are the states of matter?
• Can matter exist in three states?
• Why do you wear cotton clothes in summer?
• What are the factors that affect evaporation?
• What are the characteristic features of particles of matter?

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