Chemistry

Chemistry – Materials

  • The branch of Chemisry that deals with the study of all the elements and the properties , preparations and applications of their compounds are called – InOrganic Chemistry
  • The branches of Chemistry that deals with all aspects of Carbon and its compounds are called – Organic Chemistry
  • The Chemistry that deals with the Theoretical and Mechanical aspects of Chemical reactions are called – Physical Chemistry
  • The branches of Chemistry involves the study of Chemical changes and reactions occurring with in living systems and in life process are called – Bio Chemistry
  • The study of constituents and their identification in Chemical subsistence is called – Analytical Chemistry
  • Analytical Chemistry can either be qualitative or quantitative in nature

Matter and Its Nature

  • Every thing in this Universe is made of materials ,which scientists have named “matter they have both mass and volume”.
  • Anything that occupies space and possess weight is termed matter.
  • The amount of matter contained in any object is known as its Mass.
  • Matter can neither be created nor be destroyed ,it can onlybe changed from one from to another.
  • Early Indian Philosophers classified matter in the form of „ 5 „ basic elements that is “ Panch Tatva”.
  • They are air,earth ,fire ,sky and water.
  • Modern Scientists classified two types based on their physical properties and chemical nature.
  • One way of classification of matter is into pure substances and mixtures.
  • Another way it is classified into elements, compounds and mixtures.

Physical nature of matter

  • Matter is made up of particles.
  • The particles are very small and have space between them.
  • The particles are continuously moving due to the kinetic energy.
  • As the temperature rises, the kinetic energy of the particles also increases ,and they move faster .
  • The particles of matter attract each other due to a force acting between them and keeps them together.
  • The strength of the force of attraction varies from one kind of matter to another

States of matter

  • The matter exist in three different states, such as solid, liquid and gas.
  • The states of matter arise due to the variation in the characteristics of the particles of matter.
  • The solids have a definite shape ,distinct boundaries ,fixed volumes and have neggligable compressibility.
  • They were difficult to change their shape.
  • The liquids have no fixed shapes but have a fixed volume.
  • Liquids flow and can change shape,they are not rigid built can be called fluid.
  • The solids, liquids and gases can diffuse in to liquids.
  • The rate of diffusion of liquids is higher than that of solids.
  • This is due to in liquid state,the particles move freely and have greater space between each others.
  • The gases are highly compressible than both solids and liquids.
  • The Liquified Petroleum gas (LPG) Cylinder and Oxygen supplied to hospitals in Cylender are compressed gases.
  • The Compressed natural Gas (CNG) is used as fuel in vehicle due to its high compressibility.
  • The Gases show the property of diffusion very fast in to other gases.
  • In the gaseous state the particles move about randomly at high speed.
  • The minimum temperature at which a solid melts to become a liquid at the atmospheric pressure is called its ‘melting point’ .
  • The melting point of a solid is an indication of the strength of the force of attraction between its particles .
  • The melting point of ice is 273.15k.
  • The process of melting or change of solid state in to liquid state is called Fusion.
  • Kelvin(K) is the SI unit of temperature.
  • 0oC = 273.15K / 273K = 0oC
  • To convert a temperature on the Kelvin scale to the Celsius scale to substract “ 273 ” from the given temperature.
  • ie, K – 273 = Celsius
  • To convert a temperature on the Celsius scale to the Kelvin scale to add “ 273 “ to the given temperature. – ie , C + 273 = Kelvin
  • The amount of heat energy is required to change ‘1kg’ of solid in to liquid at atmosphere pressure at its melting point is known as the ‘ Latent heat of fusion’.
  • The particles in water at 0oC (273K)have more energy than the particles in ice at the same temperature.
  • The temperature at which a liquid starts boiling at the atmosphereic pressure is known as its ‘boiling point’. It is a bulk phenomenon.
  • Particles from the bulk of the liquid gain enough energy to change into the vapour state.
  • The temperature for water to change into vapour state is 373K. ie (373 – 273o)C = 100oCThe water vapour at 100oC have more energy than water at the same temperature is due to the “latent heat of vaporization”.
  • That is particles in the steam have absorbed extra energy in the form of latent heat of vaporization .
  • Solid state → (heat) → Liquid state → (heat) →Gaseous state.
  • Solid state ← (cool) ← Liquid state ← (cool) ← Gaseous state.
  • The state of matter can be changed in to another state by changing the temperature.
  • A change of state directly from solid to gas without into liquid state is called “Sublimation”.
  • The direct change of gas to solid with out into liquid is called ‘deposition’ .

Change of Pressure – effect

  • The difference in various states of matter is due to the difference in the distance between the constituent particles.
  • Applying pressure can reducing temperature and liquify gases.
  • Atmosphere or ‘atm ‘ is a unit of measuring pressure exerted by a gas.
  • The SI unit of pressure is pascal ‘ pa ‘.
    • 1atm = 1.01 x 105 pa.
  • The pressure of air is atmosphere is called atmospheric pressure.
  • The atmospheric pressure at sea level is 1 atm , that is normal atmospheric pressure.
  • The Solid Carbondioxide (Co2 ) is stored under high pressure due to the tendency to direct conversion of gaseous state on decrease of pressure to 1 atm.
  • Hence the solid carbondioxide is called ‘ dry ice ‘.
  • The pressure and temperature determine the state of a substance.

Evaporation

  • The phenomenon of change of a liquid in to vapours at any temperature below its boiling point is called evaporation.
  • The rate of evaporation increase with
    • An increase of temperature
    • An increase of surface area
    • A decrease in humidity
    • An increase in wind speed
  • Humidity is the amount of water vapour present in air.
  • If the amount of water in air is high ,the rate of evaporation decreases.
  • Due to evaporation clothes dry faster on a windy day.
  • Modern scientists talking of ‘ 5 ‘ states of matter such as,
    • Solid
    • Liquid
    • Gas
    • Plasma
    • Bose Einstein Condensate.
  • The plasma state consists of super energetic and super excited particles.
  • These particles are in the form of ionised gases .
  • The fluorescent tube and neon sign bulbes the gases inside the bulbes get ionised and creates a plasma glowing inside.
  • The sun and the stars glow due to the presence of plasma in them .
  • In ‘ 1920 ‘ Indian Physicist Satyendra Nath Bose had done some calculation for the ‘ 5‘ th state of matter.
  • Based on this Albert Einstein predicted a new state of matter, that is the Bose Einstein condensate (BEC).
  • In 2001 Eric. A. Cornell , Wolfang Ketterle and Carl .E. Weiman of USA received the Nobel Prize in physics for achieving “ Bose – Einstein condensation”.
  • The BEC is formed by cooling a gas of extremely low density about one hundred thousandth the density the density of normal air to super low temperature.
  • One way the matter is devided in to pure substances and mixtures.
  • Most of the matter around us exist as mixtures of two or more pure components.
    • Air – Mixture of more than 5 gases
    • Petrol – Mixture of several hydrocarbons
    • Drinking water – Mixture of pure water and several salts.
    • Milk – Mixture of water , proteins ,vitamins ,Minerals etc
  • A very few examples of the use of pure substances in daily life such as
    • Copper used in electrical wiring
    • Distilled water in car battaries
  • A solution is a homogenous mixture of two or more substances.
  • We can also have solid solutions and gaseous solutions.
    • Alloys – Solid solution
    • Air – Gaseous solution
  • In a solution there is homogeneity at the particle level.
  • The major component of a solution that dissolves the other component in it is called “ the solvent”.
  • The minor component of a solution that is dissolved in the solvent is called “ the solute”.
  • In sugar solution ,water is the solvent and sugar is the solute.
  • Air is a Mixture of gas in gas
  • The main constituents of air are,
    • Nitrogen – 78%
    • Oxygen – 21%
  • The particles of a solution are smaller than 1nm/10-9meter in diameter so they can not be seen in naked eyes.
  • The path of light is not visible in a solution
  • Depending up on the amount of solute present in a solution it can be classified in to.
    • Dialuite
    • Concentrated or
    • Saturated solution.
  • At any particular temperature a solution has dissolved as much solute as it is capable of dissolving is called a saturated solution.
  • The amount of solute present in the saturated solution at this temperature is called its “Solubility”.
  • If the amount of solute contained in a solution is less than the solution level is called an Unsaturated solution.
  • The concentration of a solution means the amount of solute present in a given amount of solution.
  • There are three main ways to expressing the concentration of a solution.
    • Mass by Mass percentage of solution
      = ( Mass of solute / Mass of solution ) x 100
    • Mass by volume percentage of a solution = ( Mass of solute / Volume of Solution ) x 100
    • Volume by volume percentage of a solution = ( Volume of solute / Volume of Solution ) x 100
  • Alloys are mixture of two or more metals or a metal and non – metal ,can be separated in to their components by physical methods.

Suspension

  • Suspension is hetrogenous mixture.
  • The solute particles do not dissolve but remain suspended through only the bulk of the medium.
  • The particles of a suspension can be seen by the naked eye.
  • A beem of light passing through it and make its path visible.

Colloidal Solution

  • A colloid is a hetrogenous mixture.
  • The size of particles of a colloid is too small
  • Colloids are big enough to scatter a beam of light passing through it and make its path visible.
  • They can not be separated from the mixture by the process of filtration.
  • A special technique of separation known as centrifugation can be used to separate the Colloidal particles.
  • The solute of colloid form the dispersed phase.
  • The solvent of colloid is known as the dispersing medium.
  • Colloids are classified according to the state of the dispersing medium and the dispersing phase.

Dispersed phase + Dispersing medium → Type of colloid

  • Liquid + Gas → Aerosol
    • eg :- Fog , Clouds ,Mist
  • Solid + Gas → Aerosol
    • eg :- Smoke , automobile exhaust
  • Gas + Liquid → Foam
    • eg :- Shaving Cream
  • Liquid + Liquid → Emulsion
    • eg :- milk , face cream.
  • Solid + Liquid → Sol
    • eg :- Milk of magnesia , mud
  • Gas + Solid → Foam
    • eg :- Foam , Rubber , Sponge , Pumice
  • Liquid + Solid → Gel
    • eg :- Jelly , Cheese , butter
  • Solid + Solid → Solid sol
    • eg :-Coloured gemstone , Milky glass

Different methods of separation

  • Seperation of the volatile component (solvent) from its non – volatile solute by Evaporation.
    • eg:- Dye from Blue or Black ink

Centrifugation

  • Principle of centrifugation – The denser particles are forced to the bottom and the lighter particles stay at the top when spun rapidly.
  • This process is applied for the separation of
    • In Diagnostic laboratories for blood and Urine tests.
    • In Diaries and home to Separate butter from cream.
    • In washing machines to squeeze out water from wet clothes.

Separation of immiscible liquids

  • The immiscible liquids separate out in layers depending on their densities.
  • Examples :-
    • To separate mixture of oil and water
    • In the extraction of iron from its ore.

Chromatography

  • It is a process of separation of components of a mixture .
  • ‘Kroma’ means colour in greek.
  • This technique was first used to separation of colours .
  • It is mainly used for separation of those solutes that dissolves in the same solvent.
  • Main applications of this technique was in the separation of
    • Colours in a dye
    • Pigments from natural colours
    • Drugs from blood

Separation of two miscible liquids

  • The method used is ‘Distillation’.
  • Its principle is that boil without decomposition and have sufficient difference in their boiling points.
  • If the difference of boiling points of mixtures were less than 25K ‘fractional distillation’ process is used.
  • Air is a homogenous mixture and can be separated into its components by “fractional distillation”
  • The Crystillaion mathod is used to purify solids.
  • It is a process that seperates a pure solid in the form of its crystals from a solution.
    • Eg :- Separation of Copper Sulphate from China dish
  • On the basis of chemical composition substance cab be classified in to elements and compounds.
  • Robert Boy le was the first Scientist to use the term element in 1661
  • The French Chemist Antoine Laurent Lavoisier was the first to establish an experimentally useful definition of an element.
  • According to Lavoisier an element is a basic form of matter that can not be broken down to simpler substances by chemical reactions.
  • Elements can be normally divided in to follows,
    • Metals
    • Non – metals
    • Metalloids
    • Ex. of Metals – Gold , Silver, Copper, Sodium, Potassium etc
  • ‘Mercury’ is the only metal that is liquid at room temperature.
    Eg. Of non – metals – Hydrogen , Oxygen , Carbon , Iodine ,Bromine, Chlorine etc
  • The elements shows intermediate properties between those of metals and non – metals
    are called Metalloids
    Eg. of Metalloids – Boron , Silicon , germanium etc
  • Naturally occurring elements are ’92’ numbers.
  • Eleven elements are “Gaseous state at room temperature”.
  • Two elements are liquid state at room temperature.
    • They are Mercury and Bromine.
  • Elements like “Gallium “ and Cesium become liquid at a temperature slightly above room temperature that is „ 303K‟.
  • The concentration of solution is the amount of solute present per unit volume or per unit mass of the Solution.
  • The dispersed phase and the dispersion medium are related to Colloids.
  • A compound is a substances composed of two or more different types of elements , chemically combined in a fixed proportion.
  • Properties of compounds are different from its
    • Constituent elements
  • Properties of Mixtures shows properties of its elements.
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