Detailed notes of MATTER IN OUR SURROUNDINGS | Class 9 | chemistry | Chapter 1

MATTER IN OUR SURROUNDINGS

MATTER

 Anything which occupies space and has mass is called matter.
 In other word, anything which has mass and volume is called matter.
 Ex- chain, table, computer, book, pen, tree etc.
According to their physical and chemical properties, matters can be divided into three types
  (i) Solid
  (ii) liquid
  (iii)gas

PROPERTIES OF MATTER

 -Matter is made up of small particles.
 -These particles have spaces between them.
 - Particles of matter attract each other because of force of attraction.

EXPERIMENT

 1: EXPERIMENT WITH POLLEN GRAINS

- If we suspend extremely small ,pollen grains in water and see though microscope, we found that the tiny particle of water do collision with
pollen grains.
- Due to these collision pollen grains move slightly.

 2: MIXING OF INK WITH WATER

 -If we put a drop of ink water, we see that initially ink is present in small
 That initially ink is present in small portion of water and after sometime,ink
 Spread up all over in the water.
 -This happen because the tiny particles of water collide with tiny particles of Ink .Due to this collision, particle of water and ink mix with each other.

 From above two experiment, its is proved that
➢ Matter is made up of tiny particles.
➢ Particles do Brownian motion.

Brownian motion of dust particle and smoke

→ Mr. Robert Brownian observed the random movement of pollen grains in water in 1872, this movement of particle is called Brownian motion.
→ Dust move randomly because the random moving particle of air collide with dust. particles
→ Similarly, smoke also move randomly because the random moving particle again and again.

Diffusion

→ The process of mixing of two substances due to Brownian, Brownian motion of particles is called Diffusion.
→ As temp. Increases, Brownian motion increase and diffusion become fast.
→ Diffusion takes place from higher concentration to lower concentration.
→ It is a natural process.
→ It takes place in solid, liquid and gas.

Three states of matter

There are three states of matter

(i) Solid

→ Solids have fixed volume and shape.
→ In solid, particle is closely packed and they have very less spacing between them.
→ In solid, particles only vibrate at their position and they have less kinetic energy.
→ The force of attraction between the particles of solid is very strong.
Ex: - Stone, wood, brick, ice, sugar, coal etc.

(ii) Liquid

→ Liquid have fixed volume but indefinite shape.
→ In liquid there is a weaker force of attraction and more spacing between the particles.
→ In liquid, particle can move around and have high kinetic energy.
Ex:-Milk, water, petrol, alcohol.

(iii) Gas

→ Gases have indefinite shape and volume.
→ Particles of gases have very large spacing and very weak attraction between them.
→ Particle of gases move around easily and have very high kinetic energy.

CHANGE OF STATE OF MATTER

→ Matter can be changed from one state to another state.
i.e - a solid can be changed to liquid and liquid can be changed into gas.

The change of state of matter mainly depend upon two factor

A.TEMPERATURE

→ By increasing the temp, a solid can be converted into gaseous state.
→ By decreasing temp, a gas can be converted into liquid state and liquid can be converted into solid state.

(a) Solid to liquid

→ The process in which a solid substance changes into a liquid on heating is called melting (fusion).
 Ex:-Ice melt to become water.
→ The temperature at which a solid substance melts and changes into a liquid at atmospheric pressure is called
melting point of the substance.
 Ex-ice melt at temp 0 degree celsius to become water so melting point of is 0 degree celsius.
→ The melting point of a solid is a measure of the force of attraction between its particles.
→ When a solid is heated sufficiently, it changes physical state and become a liquid.

(b)  Liquid to gas

→ The process in which a liquid substance changes into rapidly on heating substance changes into a gas rapidly
on heating is called boiling.
→ The temperature at which a liquid boils and changes rapidly on heating is called boiling point.
 Ex:-When water is heated at 100 degree celsius it boils to from gas called steam .So the point of water is 100 degree celsius.
→ The boiling point of a liquid measures the force of attraction between its particles.

(c) Gas to liquid

→ The process of changing a gas to liquid by steam changes into water on cooling called condensation of  steam.

(d) Liquid to solid

→ The process of changing a liquid into a solid by cooling is called freezing.
 Ex:-When water is cooled, it gets converted into solid called ice. This is called freezing of water.

LATENT HEAT

 Normally, when heat is given to substance, then its temp rises.
  This however, is not so when a change of state of a substance a takes place .Because when heat is given to change the physical state of a substance.
There is no rise in temp of the substance. The heat we supply is used up in overcoming the force of attraction between the particles of a substance during state change.

DEFINATION

The heat energy which has to be supplied to change the state of a substance is called latent heat.

The latent heat is of two types

(i) Latent heat of fusion ( solid to liquid )

The latent heat of fusion (or melting) of a solid is the quantity of heat in joules required to convert 1k.g of solid to
liquid, without any change in temp.
Ex:-Latent heat of fusion of ice is
3.34×10^5 J/kg.

(ii) Latent heat of vaporization ( liquid to gas )

  The latent heat of vaporization of a liquid is quantity of heat in joule required to convert 1kg of liquid to gas without any change in temperature.
Ex - The latent heat of vaporization of water is 22.5×10^5 J/kg.

SUBLIMATION

The changing of a solid directly into vapour on heating and of vapours into solid on cooling is
known as sublimation.
 Solid vapour

B. PRESSURE

→ The physical state of matter can also be changed by changing the pressure.
→ Gases can be liquefied by applying high pressure and lowering the temp.
→ There is a lot of space between the particles of a gas. When pressure is applied the particles get so close together that they attracting each other to from a liquid.

 Ex:-Ammonia gas can be liquefied by applying high pressure and lowering temp.

EVAPORATION

→ When liquid is left exposed to air, its volume decrease gradually. This is due to evaporation.
Definition:-The process of liquid changing into vapour even below its boiling point is known as evaporation.
→ Evaporation of liquid can take place even at room temp.
→ Whatever be the temp at which evaporation take place the latent heat of vaporization must be supplied
whenever a liquid change into vapour.
Ex:-
1. Wet clothes dry due to evaporation of water.
2. Common salt is also recovered from sea water by the process of evaporation.

FACTORS AFFECTING EVAPORATION

1. Temperature:- The rate of evaporation increase on increasing the temp. of the liquid .

2. Surface area of liquid:-The rate of evaporation increases on increasing the surface area of liquid .

3. Humidity of Air:-When humidity of air is low, then the rate of evaporation is high and when humidity of air is high the rate of evaporation is low.

4. Wind speed:-The rate of evaporation of a liquid increase with increasing wind speed.

COOLING CAUSED BY EVAPORATION

The cooling caused by evaporation is based on the fact that when a liquid evaporates ,it takes the latent heat of anything it touches, by loosing heat anything get cooled.

Ex:-1. During summer days, water is usually kept in an earthen pot to keep it cool.
 The earthen pot has a large no. of extremely small pores in its walls. Some of water continuously keeps seeping though these pores to the outside of the pot. This water evaporates continuously and takes the latent heat required for vaporization from the earthen pot and the remaining water loses heat and gets cooled.

Ex:-2 If we put a little of spirit at the back of our hand and wave it around the spirit evaporates rapidly and our hand
feels very cold.

Ex:-3 Perspiration (or sweating) is our body’s method of maintaining a content temp.

PLASMA AND BOSE-EINSTEIN CONDENSATE

PLASMA-

→ Plasma is a mixture of free electrons and ions.
→ It occurs naturally in the stars.
→ The sun and other stars glow because of the presence of plasma makes a fluorescent tube (or neon sign bulb)to glow.

BOSE EINSTEIN CONDENSATE-

→ It can be obtain by cooling a gas of extremely low density to super low temp.