MATTER IN OUR SURROUNDINGS Notes

MATTER IN OUR SURROUNDINGS CLASS 9TH SCIENCE NOTES

What is matter?

Anything that we see around us is material. So, we can say that everything in this universe is made up of material, which our scientists have named as “matter”. The air we breathe, the food we eat, cloths we wear, stones, cars, clouds, buses, roads, stars, planets, plants, animals, water, sand etc — everything is matter. 

• Matter is made up of very small particles.

State of matter 

• The matter we see around us exists in the 3 states i.e., solid, liquid and gas.

• These three states of matter depend upon the forces of attraction between the particles.
1. This force of attraction between particles is maximum in solids.
2. This force of attraction between particles is minimum in gases.
3. This force of attraction between particles of liquids is less than solids and more than gases.
• Due to variation in force of attraction, the spaces in between the constituent particles are also different in solids, liquids and gases. 

1. This space in between the constituent particles is minimum in solids.
2. This space in between the constituent particles is maximum in gases.
3. This space in between the constituent particles of liquids is more than solids and less than gases. 

• Due to variation in force of attraction, kinetic energy of the particles is also different in solids, liquids and gases. 

1. Kinetic energy of the constituent particles is minimum in solids.
2. Kinetic energy of the constituent particles is maximum in gases.
3. Kinetic energy of the constituent particles of liquids is more than solids and less than gases. 

• Due to variation in force of attraction, the arrangement of particles is also different in solid, liquid and gases.

1. Arrangement of particles in SOLIDS is in well-ordered manner.
2. Arrangement of particles in LiqUds is in little bit ordered manner, means in liquids the layers of particles can slip & slide over each other.
3. There is no arrangement of particles found in GaSES. Particles of gases, moves randomly anywhere they found space to move.

• These three states of matter are inter-convertible. The state of matter can be changed accordingly by changing temperature or pressure.
• For example, water exists in all three states i.e., ice as solid, drinking water as liquid, steam as gas. 

1. By reducing temperature and increasing pressure steam (gas) can be converted into drinking water (liquid). 
2. By further reducing temperature and increasing pressure drinking water (liquid) can be converted into ice (solid). 

Sublimation

The conversion of solid state of matter directly into gaseous state without going through the liquid state is known as sublimation.

Deposition

The conversion of gaseous state directly into solid state without going through the liquid state is known as deposition. 

Boiling

The conversion of whole (bulk) liquid state into gaseous vapour state is known as boiling. Boiling is bulk phenomenon, means every part of liquid start boiling. 

Evaporation 

The conversion of the liquid at the surface into gaseous vapour state is known as evaporation. Evaporation is surface phenomenon, means particles at the surface of liquid gain enough energy to overcome the attraction force present in between the liquid particles and change from liquid to vapour state.

• Rate of evaporation of any liquid depends upon the surface area of the liquid exposed to the atmosphere, temperature, humidity and wind speed.
• Evaporation process causes cooling, which we can see in case of soil/clay pot (matka).

Latent heat of vaporisation

The heat energy required to change the 1 kg of a liquid into gaseous state at the atmospheric pressure, at its boiling point is known as latent heat of vaporisation. 

Latent heat of fusion

The amount of heat energy required to change the 1 kg of solid into liquid state at its melting point is known as latent heat of fusion. 

Measurable physical quantities

Here are some measurable physical quantities and their units of measurement with symbol of unit.

Quantity	Unit	Symbol
Temperature	kelvin	K
Length	metre	m
Mass	kilogram	kg
Weight	newton	N
Volume	cubic metre	m3
Density	kilogram per cubic metre	kg m–3
Pressure	pascal	Pa