Matter in our Surroundings

(1) Matter is any substance that has mass and volume.

Eg:- Air, food, stone, plants etc.

(2) Physical nature of matter

(i) Matter is made up of particles.

Eg:-  Dissolve some salt in water.

Salt dissolve in water throughout and disappear in the water. The water level did not change because salt particles get in to the space between particles of the water. Therefore, it is clear that matter is made up of particles.

(ii) Particles of the matter are very small.

Eg:- Dissolve 2 – 3 crystal of potassium permanganate in 100 ml water.

Take 10 ml of this solution and put it into the 90 ml of water.

Now, repeat this experiment 5 to 6 times.

Therefore, it is clear from the experiment that a few crystal of the potassium permanganate can colour a large volume of water.

(3) Characteristics of particles of matter

(i) Particles of matter have space between them. It means particles of one matter get into the spaces of particles of other matter.

Eg:- Coffee, tea, lemonade, potassium permanganate in water etc.

(a) Coffee gets into the spaces of particles of milk or water.

(b) Lemon gets into the spaces of particles of water to prepare lemonade.

(c) Milk, sugar, water and tea leaves gets into the spaces of particles of each other to prepare tea.

(ii) Particles of matter move continuously because of kinetic energy they possess. Particles of gasses and liquid move but particles of solid only vibrate because they are very close to each other. The force of attraction is highest in the particles of solid.

Eg:- (a) Fragrance of perfume spread in room by the movement of the gaseous particles. The particles of perfume settle between the space of the particles of the air.

(b) Potassium permanganate intermix with the water.

Diffusion is the process of intermixing of particles of two different matters on their own in which particles of high concentration moves towards the particles of low concentration.

Heating increases the process of diffusion. It happens because kinetic energy of the particles increases after heating.

Eg:- Take two jars. Fill one with cold water and other with hot water. Dissolve crystal of copper sulphate in both jars.  It is observed that the process of diffusion or intermixing of the particles of matter finished in hot water jar first.

(iii) The force between the particles which keeps them together is known as force of attrcation. Therefore, particles of the matter attract each other. The strength of this force of attraction varies from one kind of matter to another.

Eg:- (a) We have to apply greater force on cutting of iron, breaking of chalk because of great force of attraction between particles of solid matter.

(b) We can not cut solution and gas because of less force of attraction between particles of liquid matter.

(4) States of Matter

(i) Solid state

Characteristics of the solid matter

(a) Solids have definite shape,ie, distinct boundaries.

Eg:- Book, pen, table , cup etc.

The shape of above articles can not be changed. A force applied on them can not change their shape. It may possible that solid can break. Therefore their outer limits and volumes are also fixed.

(b) Solids have fixed volumes.

Eg:- Pen, stool or any solid has fixed volume. A force applied on them can not change their shape. It may possible that solid can break.

(c) Solid matter has the highest force of attraction between particles in comparison of liquid and solid matter.

(d) Particles of solid matter has no free movement but they vibrate or oscillate at their position due to strong force of attraction.

(e) Particles of solid do not have space for movement due to the highest force of attraction.

(f) Solids are not compressible because force of attraction between particles is very strong.

(g) Some more examples –

(A) A stretched rubber band can regain its shape if applied force is removed.

(B) Sugar and salt are solids whether they take shape of the jar. Actually these are not taking shape of the jar but filling it. The shape of the crystal of the sugar and salt are same when we take it in hand or in jar.

(C) Yes sponge is solid with many holes in it. The holes are fills with air. When we compress it the air come out from the holes. When we remove force, the sponge regains its original shape.

(ii) Liquid state

Characteristics of the liquid matter

(a) Liquids do not have definite shape. Liquids take shape of the container in which they kept.

Eg:- Milk ,water etc. take shape of the container in which they kept.

Liquids are called fluid because they can flow and can change their shape.

(b) Liquids have fixed volume.

(c) The solids, liquids and gaseous can diffuse in liquids.

Eg:- (A) Salt diffuses in water.

(B) Colour diffuses in water.

(C) Oxygen diffuses in the water.

(d) Liquid matter has lesser force of attraction between particle than solid matter but greater than gaseous matter.

(e) Particle of liquid has little space for movement due to lesser force of attraction.

(f) Liquids are less compressible than the solids because force of attraction between particles is not as strong as in solids.

(iii) Gaseous state –

Characteristics of the gaseous state –

(a) Particles of the gaseous state do not have fixed shape.

Eg:- Air is every where.

(b) The volume of the gas is volume of the container. It means no fixed volume of the gas.

(c) The gas is highly compressible as compared to solids and liquids.

Eg:- The liquefied petroleum gas (LPG) cylinder and oxygen cylinder used in the hospitals.

(d) Particles of the gas can move freely.

Eg:- Aroma of food spread in home.

(e) Gaseous matter has least force of attraction in comparison of particles of solid and liquid matter.

(5) Matter can change its state-

(i) Effect of change of temperature

Effect of increasing temperature –

(a) Solid state to liquid state –

Kinetic energy of solid matter also increases with increase of temperature of the solid (ice). As a result, the particles of solid state start vibrating. With the increase of temperature the force of attraction between particles loosens and particles start moving. This point of temperature is known as melting point.

The melting point of any solid is the temperature at which solid stars melting or turns in to liquid.

Eg :- The melting point of the ice is 273.15 K (00C).

The melting point temperature of the system does not change till all ice melts. Even though, we continue to heat the beaker. The heat energy is used by the ice without showing any rise in the temperature. This hidden heat energy is known as latent heat of fusion.

Latent heat of fusion

(b) Liquid state to gaseous state –

Kinetic energy of liquid matter increases faster than solid state matter with increase of temperature of the liquid (water). As a result, the particles of liquid state start moving faster. With the increase of temperature the force of attraction between particles loosens and particles of liquid start changing into gaseous particles. . This point of temperature is known as boiling point.

Eg:- Boiling point of the water is 373K (1000C + 273 + 100 + 373K).

The boiling point temperature of the system does not change till all liquid vaporised. Even though, we continue to heat the beaker. The heat energy is used by the liquid without showing any rise in the temperature. This hidden heat energy is known as latent heat of vaporisation.

Latent heat of vaporisation

(c) Solid state to gaseous state-

The process in which solid matter can change in to gaseous matter directly without changing in liquid matter, is known as sublimation.

Eg:- After heating crystals of ammonium chloride changes in to vapour(gas).

Experiment –

Put some ammonium chloride (solid) on china dish covered with funnel. Place cotton on the funnel and heat the system. After some time vapours of ammonium chloride can be observe in the funnel.

Effect of decreasing temperature –

(a) Liquid state to solid state –

When liquid cools (decrease temperature), it changes in to solid state. The temperature at which liquid changes in to solid is called freezing point. The process in which liquid changes in to solid is known as solidification

Eg:- Water changes in to ice. The freezing point of the water is 00C.

(b) Gaseous state to liquid state –

When vapour or gaseous state cools down in contact of cool solid or liquid, gaseous state changes in to liquid state.

The process, in which gaseous state changes in to liquid, is called condensation.

Eg:- Air of atmosphere changes in to water droplet when it comes in contact of cold bottles.

(c) Gaseous state to solid state –

The process, in which gaseous matter can change in to solid matter directly without changing in liquid matter, is known as deposition.

Eg:- In winter water vapour comes in contact of the windows and immediately forms frost(Solid) without changing into liquid.

(ii) Effect of change of pressure-

(a) Effect of high pressure-

Liquefaction is a process in which a gas can be liquefied by applying high pressure and low temperature.

Eg:- Petroleum gas is liquefied to LPG (liquefied petroleum gas) by using high pressure and low temperature.

(b) Effect of low pressure – Solid Co2 (Dry ice) can be change in to gaseous form directly (without changing in to liquid) by applying low pressure up to 1 atmosphere.

(6)Evaporation –

Evaporation is a phenomenon in which particles of liquid present on the surface of the liquid can change into vapour at any temperature below its boiling point.

Factors affecting evaporation

(i) Increased surface area can increased the process of evaporation.

Eg :- We spread wet clothes for drying. Therefore, surface area of the cloth increased which increases the processes of evaporation.

(ii) Increase of temperature can increase the temperature of the process of the evaporation.

Eg :- Preparing tea. In the process of preparing tea, kinetic energy of liquid increases with the increase of the temperature of the liquid. As a result, force of attraction loosens up and particles of the liquid leave surface as vapour.

(iii) A decrease in humidity-

Humidity is the amount of the water that is present in the air.

If the amount of water or humidity is already high evaporation will be slow because air can hold definite amount of water.

(iv) Increase in wind speed also help in evaporation because water particles in air moves with air. Therefore, the air surrounds us have little water and evaporation become faster to compensate water level.

Eg:- Clothes dry faster in high wind speed.

Uses of evaporation –

(i)Evaporation causes cooling because particles of liquid regain energy from the surrounding which they have lost during evaporation. Therefore, loss of energy from surrounding makes surrounding cold.

Eg:- Sprinkle water on hot floor in summer.

(ii) The water evaporates taking energy from the floor. It cools down the temperature of the floor and we feel cool.

(iii) We wear cotton cloths in summer because cotton is a good absorber of the water. When we perspire, cotton absorbs it. The water absorbs heat from our body to evaporate and we feel cool.

(iv) We see water droplets on outer surface of the cold bottle. It happens because water vapour in air loses energy in contact of cold bottle. So it converts into liquid state.

Helping Topics

NCERT solutions, class 9

Practice sheet, class 9

Differences between sublimation and deposition

Differences between latent heat of fusion and latent heat of vaporisation

Is matter around us pure?