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▸ Matter is anything which has mass and occupies space. ▸ It exists in five states, viz, solid, liquid, gas, plasma and Bose-Einstein condensate. Out of which the former three are commonly seen.
The five states of matter are discussed below Solids ▸ They have definite volume and definite shape. ▸ They are incompressible and have strongest intermolecular interactions. ▸ They are very dense as compared to liquid and gas. e.g., wood, stone, iron, etc. Melting Point ▸ It is a temperature at which a substance converts from its solid state to liquid state. Melting point of ice is 0° C. ▸ Melting point decreases in the presence of impurity. Sublimation ▸ It is the process of conversion of a substance from the solid state to the gas state without passing through an intermediate liquid phase. ▸ It is used to separate a sublimate (substance undergoing sublimation like camphor, naphthalene, ammonium chloride, etc) from non-sublimate.
▸ They have definite volume but no definite shape. They take the shape of the vessel in which they are kept. ▸ They can flow, hence, considered as fluids e.g., milk, water, mercury, etc. Boiling Point ▸ It is a temperature at which vapour pressure of a liquid becomes equal to atmospheric pressure and at which a substance converts from its liquid state to gaseous state. ▸ It is different at different places. ▸ Boiling point of water at normal conditions is 100° C. ▸ It usually decreases at high altitudes, that's why, at high altitudes, the boiling point of water is less than 100°C and more time is required to cook a food. ▸ Boiling point of water in pressure cooker is high due to high pressure and hence, less time is required to cook the food. ▸ Boiling point increases in the presence of impurity. Evaporation ▸ It is the process of conversion of a liquid into vapours at any temperature below its boiling point. It increases with increase in surface area and temperature. ▸ It produces cooling. That's why we feel cool when some nail polish remover or spirit is kept on our palm.
▸ They have neither definite volume nor definite shape. They take the shape and volume of the container in which they are filled. ▸ They are highly compressible. ▸ They can flow so considered as fluids, e.g., air, oxygen and nitrogen. Condensation ▸ It is the process of conversion of gas into liquid or liquid into solid ▸ Solids, liquids and gases are inter convertible by changing the conditions of temperature and pressure. Plasma ▸ The fourth state of matter is called plasma. This state contains ionised gas with super energetic and super excited particles. ▸ Fluorescent tube contains helium (He) gas and neon (Ne) gas. Sign bulb contains neon (Ne) gas. Bose-Einstein Condensate ▸ In 1924-25, Satyendra Nath Bose and Albert Einstein gave the information about Bose-Einstein condensate. It is a state of matter of a dilute gas of boson cooled up to temperature which is very close to absolute zero or -273.15°C. In fact, it is a fifth state of matter.
Atoms ▸ It is the smallest particle of matter that takes part in chemical reactions. (by Dalton's atomic theory). ▸ It can neither be created nor destroyed (law of conservation of mass given by Lavoisier). ▸ It does not exist in free state and has a fixed atomic mass e.g., iron (Fe), gold (Au), silver (Ag), etc. Molecules ▸ These are the smallest part of the matter that exist in free state. ▸ They are formed by the joining of two or more atoms in fixed ratio (law of multiple proportions given by Dalton). ▸ They have fixed molecular mass which is obtained by adding the atomic masses of all the atoms present in a molecule, e.g., water (H2O), ammonia (NH3), carbon dioxide (CO2), etc.
A substance is said to be pure if all the constituent particles of that substance are the same in their chemical nature. e.g., all the elements and compounds are pure substances. Elements ▸ They contain only single type of atoms. Elements combine to give molecules. ▸ Examples of elements are sulphur, phosphorus , oxygen etc. ▸ Elements known at present are 118. Out of which 94 are natural. Elements which are liquid at room temperature are mercury (Hg) and bromine (Br). ▸ Elements which become liquid at a temperature slightly above the room temperature (303 K) are gallium (Ga) and caesium (Cs). ▸ Elements have the following order of abundance in earth crust : Oxygen > silicon > aluminium > iron > calcium. ▸ Elements have the following order of abundance in human body : Oxygen > carbon > hydrogen > nitrogen. Compounds ▸ These contain more than one kind of atoms. These cannot be separated into constituent atoms by simple physical methods. ▸ Their examples are silica (SiO)2 , water (H2O), sugar (C12H22O11), salt (NaCl), etc.
A substance is said to be impure, if all the constituent particles of that substance are not same in their chemical nature. Mixtures ▸ These are obtained by mixing two or more substances in any proportion. ▸ Mixtures can be homogeneous, i.e., have uniform composition throughout (e.g., salt solution, sugar solution, air, true solutions, etc) or heterogeneous, i.e.,have non-uniform composition (e.g.,mixture of salt and sugar, colloidal solutions, etc). Solutions or True Solutions ▸ These are homogeneous mixtures of two or more substances. ▸ A solution contain two components : solute (in less quantity) and solvent (in more quantity). Examples of solutions are sugar solution, tincture of iodine (solution of iodine in alcohol), aerated drinks like soda water, air, alloys, etc. ▸ Concentration of solution may be expressed by percentage, mole fraction, parts per million, gram per litre, molarity molality, normality, etc. Colloidal Solutions ▸ These are heterogeneous mixtures. ▸ These contain two phases, i.e., dispersed phase and dispersion medium. ▸ These can scatter light because of the presence of large solute particles, i.e., they show Tyndall effect and Brownian movement. ▸ Blue colour of sky is also due to scattering of light by dust particles suspended in air. ▸ They are separated by special technique like centrifugation. ▸ Colloidal solutions are coagulated by adding an electrolyte. ▸ Colloidal solutions are purified by dialysis, which is also used in the purification of blood with the help of artificial kidney machine. ▸ Coagulation found its use in purification of water by alum, stop bleeding by FeCl3 , formation of delta at the junction of sea and river. ▸ They are of following types on the basis of dispersed phase and dispersion medium.
Liquid
Gas
Aerosol Fog, clouds, mist
Solid
Aerosol Smoke, automobile exhaust
Foam Shaving cream
Emulsion Milk, face-cream.
Sol
Milk of magnesia, mud
Foam
Foam, rubber, sponge, pumice stone
Gel
Jelly, cheese, butter
Solid sol
Coloured gemstone, milky glass
A number of physical and chemical methods are used to separate the number of mixtures. Some important methods are discussed below Centrifugation ▸ It is based upon the principle that the denser particles are forced to the bottom and the lighter particles stay at the top when spun rapidly. ▸ It is used in diagnostic laboratories for blood and urine tests, in dairies and home to separate butter from cream, in washing machine to squeeze out water from wet clothes, etc. Distillation ▸ It is a method of separating mixtures based on differences in volatilities of components in a boiling liquid mixture. ▸ It is used to separate mixtures of ether and toluene, benzene and aniline, etc. Fractional Distillation ▸ It is used to separate liquids having very less difference in their boiling points. ▸ It is used to obtain pure diesel, petrol, kerosene oil, coaltar, etc from crude oil or mineral oil. ▸ It is used to separate a mixture of acetone (329 K) and methyl alcohol (338 K). Vacuum Distillation ▸ It is also known as distillation under reduced pressure. ▸ It is used for the substances which decomposes below their boiling point. ▸ It is used to obtain glycerol and H O22 and to concentrate sugarcane juice in sugar industry. Steam Distillation ▸ It is used to separate a steam volatile compound from non-volatile or non-steam volatile compounds. ▸ It is used to purify sandalwood oil, terpentine oil, aniline, nitrobenzene, etc. Crystallisation ▸ It is used to separate a mixture of inorganic solids with the help of suitable solvent. ▸ Their examples include separation of a mixture of sugar and salt by using ethyl alcohol. Chromatography ▸ It is the modern technique used for separation and purification of organic compounds. It was discovered by Tswett. ▸ It is used for the separation of coloured pigments from a plant. Reverse Osmosis ▸ It is a technique in which solvent molecules move from the solution of higher concentration to the solution of lower concentration when these are separated by semipermeable membrane and excess pressure is applied to the solution of higher concentration. ▸ It is used for desalination of sea water.
▸ It is the change which only affect the physical properties like colour, hardness, density, melting point, etc., of matter. ▸ It does not affect the composition and chemical properties of matter. ▸ Examples of physical changes are crystallisation, sublimation, boiling, vaporisation, cutting of trees, dissolving common sugar in water, etc.
▸ These affect the composition as well as chemical properties of matter and result in the formation of a new substance. ▸ Their examples are burning of fuel, burning of candle, electrolysis of water, burning of paper, photosynthesis, ripening of fruits, etc.
It states that the number of molecules present in 12 g of C-12 is called one mole, i.e., 1 mol = 6 023 × 1023 . = Avogadro's number (NA) e.g., 1 mole of atom = gram atomic weight = 6.023 × 1023 . atoms Number of moles = Mass (in gram)/Atomic weight (or molecular weight)
Mass (m), Volume (V), pressure (p) and temperature (T) of a gas are the measurable properties. The laws which inter-relate these properties are called gas laws.
▸ At constant temperature, the pressure of a fixed amount of gas (number of moles) is inversely proportional to its volume. ▸ The mathematical equation is
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