Introduction -There are a large number of things around us which we can see and feel. e.g.You can see the object in front of you. The object occupies some space.The space occupied by the object is called its volume.

                    If you pick up the object, you can also feel its weight. So you can conclude that the object has some mass.

Matter-  Anything that occupies space and  has mass and offers resistance is called matter.

           In general statement that anything or everything which occupies space and has a mass is called matter.

Example- book, copy, pen, chair, table, etc.

Substance-A substance is a kind of matter that cannot be separated into other kinds of matter by any physical process.

e.g.(i) Sugar dissolve in water can be separated from water by simply evaporating the water. Sugar is cannot be broken into its components by any physical process.

(ii) Sugar and salt are the substance because even the smallest particle of the sugar and salt are sweet and salty respectively.

Physical and chemical properties:-

Physical properties- The properties which can be determined without changing its composition are called physical properties. e.g. physical state, colour etc.

Chemical properties- The properties which can be determined only by undergoes a change in its chemical composition are called chemical properties. e.g. acidic or basic nature, reactions etc.

Physical nature of matter- Matter is not continuous and is particulate in nature i.e it is made up of particles.

Characteristics of particles of matters:-

(1) Matter is made up of particles.

(2)The particles of matter are too small to be imagined.

(3)The particles of some matter are in constant motion.

(4)The particles of matter attract each other.

(5)The particles of matter have empty space between them.

Classification of matter:-

Based on physical properties of matter:-

          Matter around you is found in different states or forms. The different forms of matter are solid, liquid and gas.

           Our body itself contains matter in all its three state.

   However all the substance do not exist in all three states. 

e.g.(i) Wood, stone  exist only in solid state.

(ii) Camphor, ammonium chloride exist only in the solid and gaseous state.

         Most of the substance may exist in all three states under different condition. e.g. water and sulphur.

The solid state:-

(i) Intermolecular force being large.

(ii) Particles come very close and they are strong held together.

(iii) Intermolecular space becomes very small.

(iv) Molecules are not free to move.

(v) However they can freely vibrate about their mean position of rest.

General properties of solids:-

(i) Shape and volume- A solid has a definite shape and volume.

            Particle cannot move away so solid retain its shape.

     For the same reason, the volume of solid is fixed.

(ii) Density- Density of a solid is high.

Mass per unit volume of a substance is called its density.

Density = Mass / Volume.

Volume is measured in cubic metre (cm^3) or in litre.

Due to strong intermolecular force particles are packed together into small volume or a space. So the density of a solid is high.

(iii) Melting point and boiling point- Melting and Boiling points of a solid are high.

Solid remains solid because its melting point and boiling point are above the room temperature.

(iv) Compressibility- Solids are incompressible i.e the volume cannot increase or decrease by applying pressure on it.

          However a porous solid like loaf, a piece of bread or sponge is an exception.

(v) Flow- Solid cannot flow.

Particles are rigid, they are not free to slip over one another.

(vi) Expansion or contraction- Solid expand or contract very little on being heated or cooled. 

Sublimation:- Process by which solid changes directly into its vapour without passing through liquid state, and the vapour directly back into the solid state.

         Solid obtained as a result of sublimation is known as the sublimate.

(vii) Diffusion- Process by which the particles of a substance may enter spontaneously into another substance.

      Movement of particles in a solid is restricted. Hence solid does not have the property of diffuse  into other solids.

         However, a few cases may be cited where diffusion takes place in solids. Two blocks of copper and zinc metal are tied firmly together and left for some years. It will be observed the block bounded together, because particle of each metals somewhat penetrated into the other.

The liquid state:-

(i) Intermolecular force of attraction is weak.

(ii) Particles are less strongly held.

(iii) Intermolecular space is large between the particles.

(iv) Intermolecular force is not so weak that's allows the particle to leave the surface of a liquid.

General properties of liquids:-

(i) Shape and volume- Liquid has no definite shape but has a definite volume.

     Liquid takes the shape of the vessel, because particles of liquid can slip over one another and settle down to take the shape of the vessels.

(ii) Density- Density of liquid is lower than that of solids.

(iii) Compressibility- Liquids can be compressed only to a small extent, that is they are almost incompressible.

(iv) Melting point and Boiling point- Melting point and Boiling point of liquid are generally lower as compared to solid.

        Melting point of liquid are lower than room temperature but boiling point are higher.

(v) Fluidity- A liquid has the property to flow.

Liquid can flow because its particles have higher kinetic energy than the particles of solid.

N:B Kinetic energy-Energy  of an object has due to its motion.

(vi) Diffusion- Since liquid have fluidity, they have the property of diffusion.

All the three States of matter are diffuse into liquids.

Rate of diffusion increases on raising the temperature.

(vii) Freezing- Transformation of a liquid into its solid state.

Temperature at which freezing occurs in liquid is freezing point.

Solidification of liquid is called freezing.

(viii) Evaporation- Conversion of liquid to the vapour state at any temperature. Below the boiling point of the liquid.

        Highly energetic particles of liquid leave the surface and go into the vapour.

Factors affecting evaporation:-

(i) Surface area available for evaporation- Greater the surface area of liquid, more will be the rate or extent of evaporation.

(ii) Increase in temperature- Increase in temperature of liquid, the rate of evaporation also increases.

(iii) Decrease in humidity- Amount of water vapour present in air is called humidity.

Decrease in humidity, increases the rate of evaporation.

(iv) Increase in wind speed- Rate of evaporation increases, if the wind speed increases.

(v) Nature of liquid- Lower the boiling point of liquid, evaporates faster.

Evaporation causes cooling- During this process some particles of liquid become more energetic and escape into air. This result in the fall of temperature. Thus evaporation causes cool surroundings.

The gases state:-

(i) Intermolecular force of attraction are weak.

(ii) Intermolecular space is large.

General properties of gases:-

(i) Shape and volume- Gas has neither a definite shape nor definite volume.

It takes the shape and volume of the vessel in which they are kept.

(ii) Density- Density of gases is lower than solid and liquid.

(iii) Melting point and Boiling point- At normal atmospheric pressure melting point and boiling point are below room temperature, lower than solids and liquid.

(iv) Compressibility- The compressibility of a gas is very high.

     Intermolecular space is very large in gas. Under pressure particles come much close together.

(v) Effect of heating and cooling- Gas can be made to expand or contract on heating or cooling.

(vi) Diffusion- Gases diffuse very rapidly.

Intermolecular space are very large and intermolecular force of attraction are quite weak between the particles. That is why diffusion is maximum among the gases.

(vii) Condensation- Conversion of gas into liquid is called condensation.

It is carried out by either by increasing the pressure or by decreasing the temperature on the gas.

Intermolecular force of attraction can also be increased by decreasing the temperature of the gas.

Condensation of water vapour takes place on a cold surface.

Dry ice- Carbon dioxide gas at very low temperature and under high pressure can be transformed into solid which appears like ice. The solid so obtained is called dry ice or drikold.

(viii) Pressure exerted by gas- The force applied by the gas particles per unit area on the walls of the vessels is called the pressure of the gas.

Pressure of air is called atmosphere pressure.

Pressure of air at sea level is 1 atmosphere and it is taken as normal atmospheric pressure.

Unit of pressure is Pascal (Pa).

1 atmosphere equal to 1.01325 X 10^5 Pa.

Pressure is normally expressed in atmosphere.

1 atmospheric = 76 cm = 760 millimetre.

NB: It is interesting to note that the effect of temperature is more important as compared to that of pressure.

   For every gas, there is a certain temperature above the gas cannot be converted to the liquid state. However the pressure on its surface may be the large of gas.

      The temperature is known as critical temperature and the corresponding pressure is called critical pressure.

Interconvertibility of the states of matter:-

Matter can be changed from one state to another

Solid< heat> Liquid <heat> Gas<cool>Liquid<cool>Solid.

Melting point of solid- Temperature at which a solid change into liquid state at atmospheric pressure is known as the melting point of the solid.

     Vapour pressure of solid and liquid becomes equal at this temperature.

Melting point of ice is at 0°C ( 273.15 K). Conversion of a liquid into solid is fusion of solid.

Latent heat of fusion- The amount of heat energy absorbed when 1 kg of a substance changes from solid to liquid at its melting point is called latent heat of fusion.

          Latent heat which means that is is hidden form as it is not visible.

     In case of solid it is known as latent heat of fusion.

Boiling point- The temperature at which a liquid is converted into gas or vapour is known as the boiling point of the liquid.

Boiling is a bulk phenomenon that is particles present in the bulk (inside) the liquid gain pressure at this temperature.

Latent heat of vaporization- Amount of heat energy absorbed when one kg of a substance changes from liquid to gas state at its boiling point is called latent heat of vaporization.

       Reverse process occurs gas changes into liquid.

The process by which the change in the state from gases to liquid takes place is called condensation or liquification.

Difference between steam and boiling water:- The temperature of both steam and boiling water is same.

     But steam causes more severe burns than boiling water does.

   Because stem contains extra heat energy in the form of latent heat of vaporization.

Measurement of temperature:- Three scales of measurement of the temperature of a system.

(i) Degree Celsius (°C), (ii) Degree Fahrenheit (°F) and (iii)  Kelvin (K).

Relation between Celsius and Fahrenheit:-

F=9/5(°C)+32.

Relation between Kelvin and Celsius:-

t°C=(273.15+t)K

Some differences:-

(1) Boiling and evaporation.

Boiling 

(i) It occurs at a particular temperature called the boiling point of liquid.

(ii) Boiling occurs from the surface as well as from below the surface of the liquid.

(iii) It does not produce cooling effect.

Evaporation

(i) It is a spontaneous process occurring at all temperatures.

(ii) It is a surface phenomenon occurs only from the surface of the liquid.

(iii) Cooling is always caused during evaporation.

(2) Gas and Vapour.

Gas

(i) It is a stable state.

(ii) Does not change into liquid easily.

(iii) It exist at room temperature.

Vapour

(i) It is unstable state. 

(ii) Changes into liquid at room temperature.

(iii) It mostly exist as liquid at room temperature.

The plasma state of matter:-

(i) It is called the fourth state of matter.

(ii) Plasma state consists of highly ionized gas in which the particle is used in super energetic and super excited States.

(iii) Plasma is produced in the sun and stars due to high temperature. It is presence of plasma that makes them glow.

Bose Einstein condensate:-

(i) It is called the fifth state of matter.

(ii) Bose Einstein condensate is a state of matter which is formed when matter has been cooled to near absolute zero (- 273°C).

(iii) American scientist succeeded in obtaining the state by super cooling a gas of extremely low density. The process is Bose Einstein condensation and this state of matter is called Bose Einstein condensate (B.E.C).