IS MATTER AROUND US PURE? Chemical classification of matter [NOTE: to be done in L.H.S ] I. a) PURE SUBSTANCE: Pure substances are elements and compounds having uniform composition of similar atoms or molecules in a fixed ratio. Eg: ELEMENTS: Substance having similar kind of atoms. Eg: H, O, Na, Cl COMPOUNDS: Pure substances in which two or more elements (dissimilar atoms) combine chemically in a fixed ratio by weight. Eg: CuSO4, BaSO4, NaOH, H2O. b) MIXTURE: Two or more substances which remain together and can be separated by simple physical methods. TYPES OF MIXTURES: i) Homogeneous mixtures: Mixtures with uniform composition. Eg: air, alloys, salt solution, lemonade, alcohol + water ii) Heterogeneous mixtures: Mixtures with non – uniform composition. Eg: soil+ water, oil +water, S + Fe fillings, chalk+water, smoke (mixture of carbon particles in air)
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IS MATTER AROUND US PURE? Chemical classification of matter
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IS MATTER AROUND US PURE?
Chemical classification of matter [NOTE: to be done in L.H.S ]
I. a) PURE SUBSTANCE: Pure substances are elements and compounds having uniform
composition of similar atoms or molecules in a fixed ratio.
Eg: ELEMENTS: Substance having similar kind of atoms. Eg: H, O, Na, Cl
COMPOUNDS: Pure substances in which two or more elements (dissimilar atoms)
combine chemically in a fixed ratio by weight. Eg: CuSO4, BaSO4, NaOH, H2O.
b) MIXTURE: Two or more substances which remain together and can be separated by
simple physical methods.
TYPES OF MIXTURES:
i) Homogeneous mixtures: Mixtures with uniform composition.
Eg: air, alloys, salt solution, lemonade, alcohol + water
ii) Heterogeneous mixtures: Mixtures with non – uniform composition.
Eg: soil+ water, oil +water, S + Fe fillings, chalk+water, smoke (mixture of
carbon particles in air)
Tabulate the differences between compounds and mixtures with examples
Compounds Mixtures
1. Compounds are formed as a result of chemical
reactions between two or more elements .
1. They are formed by simple mixing of 2 or
more constituents
2. Components of a compound are always
present in a definite ratio by mass
2.The components of a mixture may be present
in any ratio.
2. Homogeneous in nature 3. Can be homogeneous or heterogeneous.
4. Properties of a compound are entirely different
from its constituents.
4. Properties of a mixture are same as those of
its constituents.
5. Components of compound can be separated by
Chemical methods.
5. Components of a mixture can be
separated by physical methods.
6.Melting and boiling points of a compound are
fixed
6. Melting and boiling points of a mixture are
usually not fixed.
Tabulate the differences between Elements and Compounds with examples
Element Compound
1.Consists of same kind of atoms. 1.Dissimilar atoms combine in a fixed ratio.
2.Elements cannot be broken down. 2.Compounds can be broken by chemical methods
3.H,Na,Li,Pb…. 3.CO2,SiO2,H2SO4….
Q1. Air is considered to be mixture. Justify i) Air is a homogeneous mixture of different gases (N2 , O2 , CO2 , watervapour
, noble gases)
ii) The component gases retain their individual properties
iii) The components of air can be separated by physical methods (liquefaction
followed by fractional distillation)
Home work: Q The mixture of sulphur and iron filling is considered to be heterogeneous
in nature. Give reasons.
Q2. CO2 is a compound. Prove it.
i) CO2 has C and O in the ratio of 1:2
ii) C and O lose their individual properties after forming CO2.
iii) The components cannot be separated by physical methods.
iv) A compound has fixed melting and boiling point.
Homework: Solve worksheet
II. SOLUTIONS:
➢ It is a homogeneous mixture of two or more substances (also called as true solution)
➢ It has two components solute and the solvent.
Solute +solvent = solution
Eg: i) sugar + water = sugar solution
iii) Iodine + alcohol = Tincture of iodine
➢ Solute: substance which dissolves in solvent to form solution (present in less
amount)
➢ Solvent: substance in which solute dissolves to form solution (present in larger
amount)
Eg: water of sugar solution
TYPES OF SOLUTIONS:
1. Saturated solution: A solution in which no more solute can be added to form a
true solution.
Amount of solute = solubility
Eg: 36gms of NaCl dissolves completely in 100gm of water at 20OC
Note: Solubility depends on temperature.
➢ Solubility of solid in liquid increases with increase in temperature.’
➢ Solubility of a gas in liquid decreases with increase in temperature.
2. Unsaturated solution: A solution in which more solute can be added to make it
saturated.
Amount of solute < solubility
Eg: 20gm of NaCl is dissolved in 100ml of water at 20OC.
3. Super saturated solution: A solution in which some solute is left undissolved.
Amount of solute > solubility
Eg: 50gms of NaCl is present in 100ml of water at 20OC.
Tabulate the difference between [NOTE: to be done in L.H.S]
a) Homogeneous mixture and Heterogeneous mixtures with examples
b) Saturated and Unsaturated solutions with
examples CONCENTRATION OF SOLUTION:
➢ The amount of solute present in a solution.
➢ Concentration can be expressed in m/m %, v/v %, m/v%