Monday, 6 February 2017

Matter in our surrounding

Any thing which has got mass and occupy space is called matter.every matter is made up of small particles which may be atoms,molecules or ions. the spaces between the constituent particles of matter are called intermolecular spaces . The force of attraction between the constituent particles of matter are called intermolecular forces According to kinetic theory o matter.the constituent particles of every matter are in a state of continuous motion so they are associated with a definite value of kinetic energy Some examples of matter are water,air,stones,book,pen,etc
characteristics of particles of matter:-the important characteristics of particles of matter are
1)the particles of matter are very small.
2)the particles of matter have spaces between them.
3)the particles of matter are constantly moving.
4)the particles of matter attract each other.
Classification of matter:-we can classify matter on the following basis
1.On the basis of physical state of matter or physical classification of matter
2.On the basis of chemical composition of matter or chemical classification of matter
Classification of matter on the basis physical state of matter or physical classification of matter:-on this base matter can be classified into three types
A)solid             B)liquid               C)gas
A)solid:-A matter is said to be solid state if it has a fixed shape and fixed volume E g wood paper pen stone spoon etc. The important characteristics of solid are
1)The intermolecular forces of attraction in solids are very strong.
2)Due to strong intermolecular force of attraction the constituent particles in solid are very closely packed. Hence,the intermolecular spaces in solids are very small
3)The particles in a solid don't changes their position
4)solids have fixed shape as particles cant change their position
5)solids have fixed volume as the intermolecular spaces in solids are fixed at a given temperature.
6)solids  don't flow i.e.,solids are rigid
7)solids cannot be compressed much because of very intermolecular spaces
8)solids have high densities as particles in solid are very closely packed
9)In solids constituent particles have low kinetic energy
10)solids don't fill a container completely
B)Liquid:-A matter is said to be in liquid state if it  has a fixed volume but not a fixed shape.E.g., water, kerosine ,petrol diesel,ethanol etc the important characteristics of liquids are:-                                                        
1.The intermolecular forces of attraction in liquids are weak but not as weak as in gases.
2.due to weak intermolecular forces of attraction the intermolecular spaces in liquids are larger than solids but smaller than gases,
3.the particles in liquid change their position.
4.liquids don't possess a fixed as in liquid molecules change  their position.
5.liquids have a fixed volume as in liquids the intermolecular spaces are fixed.
6.liquid flow as in liquids particles changes their positions.
7.liquids cant be compressed much as intermolecular spaces are not too large.
8.liquids have lower densities than solids but higher than gases.
9.in liquids particles have high kinetic energy
10.liquids so not fill a container completely
C)Gas:-A matter is said to be in gaseous state if it neither possess a fixed shape nor a fixed volume E.g.,oxygen,hydrogen,nitrogen,carbon dioxide,etc The main characteristics of gases are:-
1.The intermolecular force of attraction gases are very very weak or negligible.
2.Due to weak force of attraction the intermolecular spaces in gases are quite large .
3.the particles in a gas change their position.
4.gases don't possess a fixed shape as in gases particles changes their positions
5.Gases don't have a fixed volume as the intermolecular spaces don't remain constant
6.Gases flow as in gases particles change their positions
7.Gases can be compressed much.
8.Gases have very low densities
9.In gases particles have high kinetic energy
10.Gases fill a container  completely.

Diffusion:-Diffusion can be defined as the process of intermingling of substances.in other words,the spreading out or mixing of a substances within the another substances is called diffusion.diffusion is based on the motion of the particles of the matter.diffusion occurs in solids,liquids as well as in gases.however,diffusion is fastest in gases and slowest in solids.this is because in gases, particles move very rapidly on increasing the temperature the kinetic energy of the molecules or particles increases and molecules move more rapidly,hence rate of diffusion increases
Some examples of diffusion:-when we lit an incense (agar agar) in a corner of our room,its fragrance spreads into the whole room very quickly. the fragrance of burning incense stick spreads all around due to the diffusion of its aroma into the air
2.If we take a jar full of reddish brown bromine vapours and invert another gas jar  containing air over it, then after some time the upper jar also becomes reddish brown this is because of the diffusion of the bromine vapour into the air
Temperature and Scales of temperature:-the degree of hotness or coldness of a body is called temperature there are many scales for expressing the temperature if the substance the important and commonly used among them are :-
Celsius scale  and kelvin scale
1)Celsius scale:-the most common unit of measuring temperature is degree Celsius which is written in short form as °C . The melting point of ice on this scale is   0°C and the boiling point of water is 100°C
kelvin scale:-this scale is mainly used by the scientists for research work.The S.I.unit of temperature is kelvin which is denoted by the symbol ''K''. The melting point of ice on this scale is 273 K and boiling point of water is 373K
relation between Celsius scale and kelvin scale:-since the melting of ice on the Celsius scale is 0*c and on the kelvin scale is 273k .
therefore,0°C =  273k
so,    1°C  = 1°C + 0°C=(1+273)k
2°C = 2°C+ 0°C =(2+273)k
3°C=3°C+0°C= (3+273)k so on
n°C=n°C+0°C=(n+273)k
Thus,the relation between Kelvin scale and Celsius scale can be written as
K=C + 273
Where k= temperature in Kelvin scale and C = temperature in Celsius scale
change in the state of matter:-matter can exist in three physical states, solid, liquid,and gas.for example water can exist as solid in the form of ice ,as liquid in the form of water and as gas in the form of vapour we can change the physical state of matter by changing the intermolecular spaces this can be achieved either by changing the pressure or temperature or both ,thus physical state of matter can be changed by the following two ways,
1 By changing the temperature.  2 By changing the pressure
1.Effect of change of temperature. on physical state:-This can be discussed in detail as under,
Melting and melting point:-The process of converting aa substance from its solid state into liquid state by heating it is called melting or fusion. So, when ice changes into water on heating itis called melting or fusion of ice. The temperature at which melting takes place is called melting point. For example melting point of ice is 0°C and that of wax is 63°C. the melting point of a solid is a measure the of force of attraction between its particles. Higher the melting point , greater will be the force of attraction  between its particles and vice versa
why a solid becomes liquid on heating:-A solid becomes liquid on heating because when a solid is heated heat energy makes its particles vibrate more vigorously At the  melting point the particles of the solid have sufficient kinetic energy to overcome the strong forces of attraction holding them in fixed position and the particle move away from each other and the solid melts and becomes a liquid
b)boiling and boiling point:-The process in which a liquid changes into a gas rapidly on heating is called boiling During boiling the vapours don't come out from the surface only but also from the bulk of the liquid too The temperature at which a liquid boils is called boiling point For example boiling point of water is 100°C  and that of the alcohol is 78°C the boiling point of the liquid is a measure of intermolecular force of attraction between the particle of the liquid Higher the boiling point of the liquid higher will be the forces of attraction between its particles and vice versa
Why a liquid becomes vapour or gas on boiling :-A liquid boils on heating because when a liquid is heated, the heat energy makes its particles vibrate more vigorously .at the boiling point 'the particles of the liquid  have sufficient kinetic energy to overcome the force of attraction  holding them and the particles move away from each other and the liquid boils  ,i.e,changes into vapour or gas .
C)Evaporation:-The process of converting a liquid into vapour below its boiling point is called evaporation.Evaporation takes place at every temperature some particles of liquid always have more kinetic energy than the other So,even when a liquid is well below  its boiling point some of its particles have enough energy to break the force of attraction between the particles and escape from the surface of  the liquid in the form of vapour thus the fast moving particle of a liquid are constantly escaping from the liquid to form the vapour or gas
D)Condensation :-the process of changing a substance from its vapour or gas state into a liquid state by cooling it is called condensation During condensation the energy of the vapour particles decreases and they come closer to form a liquid
2Effect of pressure on the physical state or liquefaction of gases:-the physical state of matter can also be changed by changing the pressure for example  gases can be changed into liquid by increasing the pressure and lowering the temperature this conversion of gas into liquid by increasing the pressure and decreasing the temperature is called liquefaction of gas when a gas is compressed the particles of the gas come closer to each other and start attracting each other strongly then,the gas starts changing into a liquid During compression heat is produced so it is necessary to cool the gas to lower its temperature Thus cooling helps to lower the temperature of the compressed gas and to liquefy it the liquefaction of the gas is diagrammatically illustrations as below
latent heat:-Latent heat of a substance can be defined as the amount of heat required to change the physical state of a unit mass or 1kg of the substance without changing the temperature of the substance whenever we have to change the physical state of a substance we have to supply its latent heat the S.I. unit of latent heat is j/kg there are the following two types of latent heat
1)latent heat of fusion       2)latent heat of vaporization
1)latent heat of fusion:-latent heat of fusion of a substance can be defined as the amount of heat required to change  1kg of the substance from its solid state into its liquid at its melting point For example latent heat of fusion of ice is 3.4 x 10 j/kg
2)latent heat of vaporization;-latent heat of vaporization of a substance can be defined as the amount of heat required to change 1kg of the substance from its liquid state into its vapour state at its boiling point for example,latent heat of vaporization of water is 22.5x10
factors affecting evaporation ;-The evaporation of a liquid depends or is affected by the following factors
1)Temperature;-The rate of evaporation increases with the increase in temperature and kinetic energy of molecules increases and by decreasing temperature the kinetic energy of the molecules decrease
2)surface area of the liquid:-The rate of evaporation increases with increase in the surface area and decrease with the decrease in the surface area.The washed clothes spread out ,while drying to increase their surface area for rapid evaporation of water present in them
3)Humidity in air:-higher the humidity in air lower is the rate of evaporation and lower the humidity higher is the rate of evaporation
4)wind speed:-The rate of evaporation increases with the increase in the speed of the wind and decreases with the decreases in the speed of wind. this is why clothes dry out quickly when there is wind than there is no wind
Sublimation;-There are some solids which change directly into vapour on heating and their vapours change directly into solid on cooling.This process of changing a solid directly into vapour upon heating or the process of changing vapour into solid on cooling  is called as sublimation sublimation can be represented as
                               Solid ↔ vapour
 the solid which undergo sublimation is called sublime the solid obtained by cooling of vapour is called sublimate the common substances which undergo sublimation are
Ammonium chloride,camphor,napthaline, iodine,anthracene,solid carbon dioxide,etc
Humidity and relative humidity:-The moisture present in air is called humidity,the amount of moisture that air can hold depends upon the temperature of air . at a given temperature , air can hold a definite amount of moisture or water vapours in it .the air containing the maximum amount of moisture it can hold a given temperature is called saturated air The humidity or the degree of humidity of air is generally expressed in terms of relative humidity the relative humidity of air at a given temperature is the ratio of mass of water vapours actually present in a certain volume of air to the mass of water vapours required to saturate the same volume of air at the same temperature multiplied by 100
therefore,relative humidity=mass of water vapour actually present in a given volume x 100/mass of water vapour required to saturate the same volume of air
the relative humidity is measured by an instrument called hygrometer

Note:-1.1 The relative humidity of about 50%is considered comfortable. Under these condition the sweat from our bodies evaporates readily and the air feels cool and dry. The washed clothes dry quickly under these conditions
2.when the relative humidity is very low (say 20%) the air feels very dry the moist surfaces inside the nose and throat tend to dry and produce a feeling of irritation our lips also dry and cracks appear in them
3.when the relative humidity is very high (say 80%)the air feels moist the sweat from our body does not evaporates readily and we feel hot and uncomfortable washed clothes do not dry easily under these conditions as the air already contains a lot of moisture
4.A relative humidity of 100% means the air is saturated with water vapours 

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