Understanding matter
Understanding Matter
Pure Substances
Definition
Element: An element is a pure chemical substance which cannot be broken down into simpler
substances by chemical reaction.
Compound: A compound is a substance composed of two of more elements chemically combined
with one another in a fixed proportion.
Elements can be further classified as metals, non-metals and metalloids (elements that show
characteristics of both metals and non-metals.
Properties of metals, non-metals and metalloids
Metals
Non-metals
Metalloids
Activity: Compounds
Requirement: Iron filings and sulphur powder and iron sulphide.
Crush iron filings and mix it with sulphur. Take some amount of this mixture and heat it strongly.
Compare the physical properties (color, texture, magnetism) of the initial mixture with that of the
substance obtained by heating the mixture.
Property
Color
Texture
Attracted towards a magnet
Mixture of iron filings and
sulphur powder
Iron sulphide
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Understanding matter
Take some iron filings in one test tube, mixture of iron filings and sulphur powder in another and
iron sulphide in the third. Add dilute hydrochloric acid or dilute sulphuric acid to the three samples.
You will observe some gas is released in each case. Identify the gases and write balanced chemical
equations to represent the reactions taking place.
Mixture
Definition
A mixture is a made up by two or more different substances which are mixed together but are not
combined chemically.
Activity: Different types of mixtures
Requirements: Few crystals of copper sulphate, potassium permanganate, common salt, sugar and
water.
Take two beakers with 50 ml of water. Add a few crystals of copper sulphate in one beaker and few
crystals of potassium permanganate in the second beaker.
Take two petri dishes and mix potassium permanganate with salt in one and copper sulphate with
sugar in another.
Observe the mixtures obtained by you.
Components mixed together
Is the mixture uniform in color Homogenous / Heterogeneous
and texture?
mixture
H2O + CuSO4
Uniform
H2O + KMnO4
KMnO4 + NaCl
CuSO4 + C12H22O11
Homogenous
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Understanding matter
Solution
Activity: Properties of a solution
Requirements: Few crystals of copper sulphate and water.
Take 25 ml of water in a test tube. Add few crystals of copper sulphate to it. Is the resulting mixture
homogenous?
Can you see the particles of CuSO4 in water?
Can you separate CuSO4 from water using filtration?
Shine some light on test tube from one side. Can you see the path of light through the solution?
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Understanding matter
Properties of a solution
Definition
A homogenous mixture of two or more substances is called a solution.
In such a mixture, a solute is dissolved in another substance, known as a solvent. The solvent does
the dissolving.
Definition
Saturated solution:
Concentration of a solution is the amount of solute present in a given mass of solvent.
Two commonly used methods to represent concentration are –
Sample Problem
Calculate the concentration of a solution containing 40 g of common salt in 360 g of water.
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Understanding matter
Suspension
Activity: Properties of a suspension
Requirements: Some chalk power and water.
Take 25 ml of water in a test tube. Add some chalk powder to it. Is the resulting mixture
homogenous?
Can you see the particles of chalk in water?
Can you separate chalk from water using filtration?
Shine some light on test tube from one side. Can you see the path of light through the solution?
Properties of a suspension
Definition
A suspension is a heterogeneous fluid containing solid particles that are sufficiently large for
sedimentation.
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Understanding matter
Colloid
Activity: Properties of a colloid
Requirements: One teaspoon milk and water.
Take 25 ml of water in a test tube. Add few drops of milk to it. Is the resulting mixture
homogenous?
Can you see the particles of milk in water?
Can you separate milk from water using filtration?
Shine some light on test tube from one side. Can you see the path of light through the solution?
Properties of a colloid
Definition
A colloid is a suspension of very small particles dispersed in another substance.
A colloidal system consists of two separate phases: a dispersed phase (particles which are dispersed)
and a dispersion medium (substance in which the particles are suspended).
Tyndall effect
The Tyndall effect, also known as Tyndall scattering, is light scattering by particles in a colloid or
particles in a fine suspension.
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Understanding matter
Separating components of a heterogeneous mixture
Identify the principle used and the type of heterogeneous mixture that can be separated by each of
the methods indicated below.
Magnetism
Evaporation
Decantation
Filtration
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Understanding matter
Distillation
Fractional distillation
Centrifuge
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Understanding matter
Sublimation
Chromatography
Gravitational separation
Checkpoint
How can you obtain pure CuSO4 from an impure sample?
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