Matter In Our Surroundings Class 9 Short Notes | Chapter 1

CBSE Class 9 Science Notes Chapter 1 Matter In Our Surroundings

Introduction

Everything that has mass and consume space is referred to as matter. hydrogen and oxygen, sugar and sand, air, etc. Small, minuscule particles make up matter. Due to the space between them, matter particles are attracted to one another.

States of Matter

: It has 3 states

Solid	Liquid	Gas
have strong intermolecular force	weak intermolecular force	very weak intermolecular force
very less inter molecular space	large intermolecular space	very large intermolecular space
have define shape and volumne	do not have definite shape but have definite volume	No definite shape and volumne
have high density	density is low	very low density
solid cannot be compressed	liquids can be compresssed	Gases can be highly compressed

Atomic view of the three states of matter

Physical Nature of Matter

Matter is made up of particles.
The particles are very small in size.
These particles have spaces between them.
These particles are constantly moving.
Particles attract each other.
There are 3 states of matter- solids, Liquids and Gases.
Matter can change state from one form to another.

Characteristics of Particles of Matter

Matter

Matter is a substance made up of various types of particles that occupies physical space.

The important characteristics of particles of matter are the following:

The particles of matter are very, very small.
The particles of matter have space between them.
The particles of matter are constantly moving.
The particles of matter attract each other.

The particles of matter are very, very small:

The very, very small size of particles of matter can be shown by performing the following experiment by using potassium permanganate and water.

Take 2-3 crystals of potassium permanganate and dissolve them in 100 ml of water in a beaker. We will get a deep purple colored solution of potassium permanganate in water.
Take out approximately 10 ml of this solution and put it into 90 ml of clear water in second beaker. Due to this dilution, the color of potassium permanganate solution in the second beaker becomes a bit lighter.
Take out 10 ml of this solution and put it into another 90 ml of clear water in third beaker. The color of solution will become still lighter.
Keep diluting the solution like this 5 to 8 times.
In this way, we get a very dilute solution of potassium permanganate in water but the water is still colored.
This experiment shows that just a few crystals of potassium permanganate can colour a large volume of water.
So we conclude that there must be millions of tiny particles in just one crystal of potassium permanganate, which keep on dividing themselves into smaller and smaller particles.

The particles of matter have space between them:

The spaces between the particles of matter can be shown by performing the following experiment by using water and sugar.

Take a 100 ml beaker.
Fill half the beaker with water and mark the level of water.
Dissolve some sugar (50gm) with the help of a glass rod.
We will find that the level of sugar solution in the beaker is at the same mark where water level was initially in the beaker.
When sugar is dissolved in water, its crystals separate into very fine particles. These particles of sugar go into the spaces between the various particles of water due to which there is no change in the volume of water on dissolving sugar in it.
The fact that there is no change in volume on dissolving sugar in water tells us that there are spaces between the particles of water.

The particles of matter are constantly moving:

The best evidence that particles of matter are constantly moving comes from the experiments on diffusion and Brownian motion.
The particles of matter are constantly moving can be shown by performing the following experiment by using potassium permanganate and water.
As in above.
If we carry out this experiment by using hot water in the beaker (or gas jar), we will find that the water turns purple at a faster rate. This is because, on heating, the particles of water and that off potassium permanganate gain kinetic energy and move faster. And due to faster movements, they mix into each other more quickly.

The particles of matter attract each other:

There are some forces of attraction between the particles of matter which bind them together.
The force of attraction between the particles of the same substance is known as cohesion.
If we take a piece of chalk, a cube of ice and an iron nail, and beat them with a hammer, we will find that it is very easy to break the piece of chalk into smaller particles, it requires more force to break a cube of ice, whereas the iron nail does not break at all even with a large force.
This shows that the force of attraction between the particles of chalk is quite weak; the force of attraction between the particles of ice is a bit stronger whereas the force of attraction between the particles of iron nail is very, very strong.

Diffusion

Spreading out and Mixing of one substance with another.

1. It happens in all form of matter-Solids, Liquids and Gases

2. It is fastest in gases and slowest in solids.

Can Matter Change Its State?

‘Yes’. It can definitely change its shape, size, and volume

Change of States of Matter

Matters can be changed from one state to another state. A solid can be changed into liquid and a liquid can be changed into gas. Most of the metals, which are solid, turn into liquid on heating and turn into vapour on further heating.

The change of state of matters depends upon mainly two factors:

Temperature
Pressure

Effect of Temperature

Solids change into liquid with increase in temperature. (Solid → Liquid)
A liquid changes into gas by increase in temperature. (Liquid → Gas)
Gas changes into liquid by decrease in temperature. (Gas → Liquid)
liquid changes into solid by decrease in temperature. (Liquid → Solid)

Melting

Melting is a physical process that causes a matter’s phase change from solid to liquid. When the internal energy of solid increases, usually due to the application of heat or pressure, the temperature of the matter rises to the melting point. Melting is the transformation of a solid into a liquid. The melting point is the temperature at which something melts.

For example: When ice cubes are removed from the freezer and brought to room temperature, they turn into a liquid. As a result, the ice cube melts and turns into water.

Fusion

The Phenomenon of change in solid into liquid is termed as Fusion.

For instance- Melting of Ice.

Boiling

Boiling is the fast evaporation of a liquid that occurs when it is heated to its boiling point, which is the temperature at which the liquid’s vapour pressure equals the surrounding atmosphere’s pressure. Boiling is the transformation of a liquid substance into a gas when heated rapidly. The boiling point is the temperature at which something begins to boil.

For example: “Boiling of water” refers to the quick transformation of water into steam or water vapour when heated.

Latent heat of Fusion

During the melting of solid, the temperature remains the same. The heat gets used up in overcoming the force of attraction between the particles of matter. The heat energy is being absorbed by solid ice without any rise in temperature. The heat is regarded to be hidden in the contents of the container and is called latent heat.

Latent heat of Vaporisation

The term latent heat of vaporisation can be defined as the amount of heat needed for the conversion of 1 kg of liquid at its boiling point to gas at same temperature. It differs among different liquids.

Sublimation

Sublimation is the process of a substance going from a solid to a gaseous state without transitioning to a liquid state (or vice versa). Sublimation is the term used to define the process of the water cycle to describe the process of snow and ice converting into water vapour in the air without first melting into water.

For example: When dry ice (a frozen form of carbon dioxide) is exposed to air, it instantly transforms from a solid to a gaseous state, which is visible as fog.

Effect of Pressure

The physical state of matter can also be changed by increasing or decreasing the pressure to it. Gases can be liquefied by applying pressure and lowering temperature. When high pressure is applied to a gas, it gets compressed, and when in addition to it we lower its temperature, it gets converted into liquid. So, we can also say that gases can be turned into liquids by compression and cooling.

Solid:

There is no effect of pressure on solids.

Solids are non compressible, i.e. solids cannot be compressed as there is no space between their particles which could allow compression.

When the pressure is increased on a solid, it is deformed and finally broken.

Liquid:

There is no effect on pressure on liquid. Liquids are non compressible, i.e. liquids cannot be compressed since there is not enough space between their particles to get compressed.

Gas:

The volume of gas decreases with increase in pressure. Since there is lot of space between the particles, gas is highly compressible. Large volume of gas can be compressed to a small volume. Because of this nature high comprehensibility, gas is transported easily after compressed to a small volume in cylinders.Natural gas is compressed to small volume and packed in cylinders. It is used widely as fuel to running vehicles. Because of compression it is called Compressed Natural Gas or simply known by CHG (Compressed Natural Gas).Oxygen is compressed and packed in small cylinders, which is used to save life in hospitals. On increasing more pressure gas turns into liquid.

Evaporation

The process of conversion of a liquid into vapour (or gas) at its boiling point is called evaporation. Some particles in liquid always have more kinetic energy than the others. So, even when a liquid is well below its boiling point, some of its particles have enough energy to break the forces of attraction between the particles and escape from the surface of the liquid in the form of vapour. Thus the fast moving particles of a liquid are constantly escaping from the liquid to form vapour or gas. Temperature, surface area of liquid, humidity, and wind speed are factors that affect evaporation. Evaporation causes cooling effect.