Class 9 Science Exploring Mixtures and Their Separation Notes
Class 9 Science Exploring Mixtures and Their Separation Notes
🔹 1. What is a Mixture?
A mixture is a combination of two or more substances that are not chemically combined.
Key Features:
Components retain their own properties
No fixed composition
Can be separated by physical methods
Examples:
Air
Salt + sand
Sugar dissolved in water
🔹 2. Types of Mixtures
(a) Homogeneous Mixture
Uniform composition throughout
Components are not visible
Examples:
Salt solution
Air
(b) Heterogeneous Mixture
Non-uniform composition
Components can be seen separately
Examples:
Oil + water
Sand + iron filings
Basis of Difference
Homogeneous Mixture
Heterogeneous Mixture
Composition
Uniform throughout
Non-uniform
Visibility of Components
Components cannot be seen separately
Components can be seen separately
Number of Phases
Single phase
Two or more phases
Distribution of Particles
Evenly distributed
Unevenly distributed
Appearance
Same throughout
Different in different parts
Examples
Salt water, air, sugar solution
Sand and water, oil and water, salad
🔹 3. What is a Solution?
A solution is a homogeneous mixture made of:
Solute → substance that dissolves
Solvent → substance that dissolves the solute
Example: Salt (solute) + Water (solvent)
Types of Solutions:
Solid in liquid (salt water)
Liquid in liquid (alcohol + water)
Gas in liquid (oxygen in water)
Types of Solutions on the basis of the physical state of the solvent.
Type of Solution
Solvent
Solute
Example
Solid in Solid
Solid
Solid
Brass (zinc in copper)
Solid in Liquid
Liquid
Solid
Salt in water
Liquid in Liquid
Liquid
Liquid
Alcohol in water
Gas in Liquid
Liquid
Gas
Carbon dioxide in soft drinks
Gas in Gas
Gas
Gas
Air
Liquid in Solid
Solid
Liquid
Amalgam
🔹 4. Concentration of a Solution
Indicates how much solute is present.
Terms:
Dilute solution → less solute
Concentrated solution → more solute
Types of Solutions on the basis of Amount of Solute
Type
Meaning
Dilute Solution
Contains small amount of solute
Concentrated Solution
Contains large amount of solute
Saturated Solution
Cannot dissolve more solute at a given temperature
Unsaturated Solution
Can dissolve more solute at a given temperature
Three Way of expression concentration of Solution in Percentage
Type
Meaning
Formula
Example
Mass Percentage (Mass %)
Mass of solute present in 100 g of solution
Mass % = (Mass of solute ÷ Mass of solution) × 100
10 g salt + 90 g water → (10/100) × 100 = 10%
Volume Percentage (Volume %)
Volume of solute present in 100 mL of solution
Volume % = (Volume of solute ÷ Volume of solution) × 100
25 mL alcohol in 100 mL solution → (25/100) × 100 = 25%
Mass by Volume Percentage (Mass/Volume %)
Mass of solute in grams present in 100 mL of solution
Mass/Volume % = (Mass of solute (g) ÷ Volume of solution (mL)) × 100
8 g glucose in 100 mL solution → (8/100) × 100 = 8%
Which Method is Used When?
Method
Used When
Example
Mass % (Mass by mass)
When both solute and solvent are solids or liquids measured by mass
Salt in water, sugar in water
Volume % (Volume by volume)
When both solute and solvent are liquids measured by volume
Alcohol in water, petrol in kerosene
Mass/Volume %
When solute is solid and solution is liquid (mass in volume)
Glucose in water, salt in water (solutions used in labs/medicine)
Easy Trick to Remember:
Solid + Liquid → Mass/Volume %
Liquid + Liquid → Volume %
General mixture by weight → Mass %
Solubility :
Solubility is the maximum amount of solute that can dissolve in a given amount of solvent at a specific temperature.
Example : 36 g of salt dissolves in 100 g water → its solubility is 36 g per 100 g water.
Factors Affecting Solubility
Temperature: increases solubility of solids
Pressure: affects gases (more pressure → more solubility)
Nature of substances: like dissolves like
Notes:
Maximum amount dissolved = saturated solution
More solute can dissolve = unsaturated solution
5. Methods of Separation
Separation Methods for Homogeneous Mixtures
A homogeneous mixture has a uniform composition throughout (like salt solution, sugar solution, air).
Methods of Separation:
Method
Used For
Principle
Evaporation
Salt from salt solution
Solvent evaporates, solute remains
Crystallization
Purified solid from solution (like sugar, copper sulphate)
Formation of pure crystals on cooling
Simple Distillation
Separating liquid + dissolved solid (water from salt solution)
Difference in boiling points
Fractional Distillation
Separating mixture of liquids (alcohol + water)
Different boiling points
Chromatography
Separating dyes/inks in ink
Different rates of movement on paper
Homogeneous mixtures are separated mainly based on:
Boiling point differences
Solubility differences
Rate of movement (chromatography)
Crystallization
Crystallization is a process used to obtain a pure solid substance in the form of crystals from its solution.
Principle:
It is based on the fact that a solid becomes less soluble in a solvent at lower temperatures, so it forms crystals on cooling.
Procedure
A hot saturated solution is prepared.
The solution is allowed to cool slowly.
Pure crystals of the solute are formed.
Crystals are separated and dried.
Example:
Purification of copper sulphate crystals
Obtaining pure sugar crystals from impure solution
Advantages:
Gives pure solid crystals
Removes impurities better than evaporation
Useful for heat-sensitive substances
🧠 Key Point:
Crystallization is a better method than evaporation because it gives pure and well-shaped crystals.
Crystal
Meaning:A crystal is a solid substance in which particles are arranged in a fixed, regular, and repeating pattern.
Crystals are formed when a substance solidifies slowly from a solution or melt, allowing particles to arrange properly.
Crystals have:
A definite shape
A fixed structure
Flat surfaces and sharp edges
Examples:
Sugar crystals
Salt crystals
Copper sulphate crystals
Snowflakes (natural crystals)
Distillation
Meaning:
Distillation is a method used to separate a liquid from a solution or to separate two liquids with different boiling points by heating and then cooling.
difference in boiling point = minimum 25 degree C
Principle:
It is based on the difference in boiling points of substances.
Process:
The mixture is heated in a distillation flask.
The liquid with lower boiling point evaporates first.
Vapour is cooled in a condenser and turns into liquid.
The pure liquid is collected separately.
Types of Distillation:
Type
Used For
Simple Distillation
Separating liquid from dissolved solid (salt water → water + salt)
Fractional Distillation
Separating two liquids (alcohol + water)
Examples:
Getting pure water from salt water
Separating alcohol and water
🧠 Key Point:
Distillation gives a pure liquid by using evaporation + condensation.
1. Handpicking
Used when impurities are visible and in small quantity
Example: Removing stones from rice
2. Sieving
Separates particles based on size
Example: Flour and bran
3. Winnowing
Uses wind to separate lighter and heavier particles
Example: Husk from grains
4. Magnetic Separation
Uses a magnet
Example: Iron from sand
5. Sedimentation & Decantation
Sedimentation: heavier particles settle down
Decantation: clear liquid is poured off
6. Filtration
Separates insoluble solids from liquids
Example: Tea leaves from tea
7. Evaporation
Liquid changes into vapor leaving solid behind
Example: Salt from seawater
8. Condensation
Vapor changes back to liquid
9. Distillation
Separates liquids based on boiling points
Used for pure liquids
10. Separating Funnel
Used for immiscible liquids
Example: Oil and water
🔹 6. Importance of Separation
To remove unwanted substances
To obtain useful components
To purify substances
🔹 7. Key Differences
Mixture vs Pure Substance
Mixture
Pure Substance
Variable composition
Fixed composition
Components retain properties
New properties
Can be separated physically
Cannot be separated easily
Types of Separation Methods
Method of Separation
Used For
Example
Handpicking
Removing large impurities by hand
Stones from rice
Threshing
Separating grains from stalks
Wheat grains from stalk
Winnowing
Separating lighter and heavier components using wind
Husk from grains
Sieving
Separating particles of different sizes
Flour and bran
Sedimentation
Heavier insoluble particles settle down in water
Mud in water
Decantation
Pouring out clear liquid after sedimentation
Separating water from sand
Filtration
Separating insoluble solids from liquids
Tea leaves from tea
Evaporation
Separating dissolved solid from liquid
Salt from seawater
Condensation
Converting vapour into liquid
Distilled water formation
Churning
Separating butter from curd
Butter from milk
Magnetic Separation
Separating magnetic substances
Iron filings from sand
Sublimation
Separating substances that sublime
Camphor from salt
Distillation
Separating liquids with different boiling points
Alcohol and water
Chromatography
Separating colored substances
Colors in ink
Fill in the Blanks Q
A mixture is a __________ combination of substances.
Components of a mixture retain their __________.
Mixtures have __________ composition.
A homogeneous mixture has __________ composition throughout.
A heterogeneous mixture has __________ composition.
Air is a __________ mixture.
Soil is a __________ mixture.
A solution is a __________ mixture.
The substance that dissolves is called __________.
The substance that dissolves solute is called __________.
Salt dissolved in water is a __________.
In salt solution, salt is the __________.
In salt solution, water is the __________.
A dilute solution has __________ solute.
A concentrated solution has __________ solute.
Oil and water are __________ liquids.
Miscible liquids __________ completely.
Immiscible liquids do not __________.
Suspension particles are __________ visible.
Colloidal particles are __________ visible.
True solutions are __________ transparent.
Tyndall effect is shown by __________.
Filtration is used to separate __________ solids from liquids.
The solid left on filter paper is called __________.
The liquid that passes through filter paper is called __________.
Evaporation changes liquid into __________.
Condensation changes gas into __________.
Distillation is based on difference in __________ point.
Separating funnel is used for __________ liquids.
Winnowing uses __________ to separate particles.
Magnetic separation uses a __________.
Handpicking is used for __________ impurities.
Sieving separates substances based on __________.
Sedimentation is the settling of __________ particles.
Decantation is pouring out __________ liquid.
Filtration separates __________ solids from liquids.
Salt can be obtained from seawater by __________.
Tea leaves are removed by __________.
Iron filings can be separated using a __________.
Husk is separated from grains by __________.
Flour is separated from bran by __________.
Mud settles down during __________.
The clear liquid above sediment is called __________.
A mixture with visible particles is __________.
A solution has __________ particle size.
A suspension has __________ particle size.
A colloid has __________ particle size.
Brownian motion is observed in __________.
Milk is an example of a __________.
Fog is a __________ in gas mixture.
Air is mainly composed of __________ gases.
Oxygen is present in air as a __________.
Carbon dioxide in air is a __________.
A pure substance has __________ composition.
A mixture can be separated by __________ methods.
Compounds are separated by __________ methods.
A physical change does not form a __________ substance.
In evaporation, liquid changes into __________.
In filtration, filter paper acts as a __________.
Separation of mixtures is done to obtain __________ substances.
Answer Key – Fill in the Blanks
Q
Ans
Q
Ans
Q
Ans
1
physical
21
completely
41
sieving
2
properties
22
colloids
42
sedimentation
3
variable
23
insoluble
43
supernatant
4
uniform
24
residue
44
heterogeneous
5
non-uniform
25
filtrate
45
very small
6
homogeneous
26
vapour
46
medium
7
heterogeneous
27
liquid
47
intermediate
8
homogeneous
28
boiling
48
colloids
9
solute
29
immiscible
49
colloid
10
solvent
30
wind
50
liquid
11
solution
31
magnet
51
nitrogen
12
solute
32
large
52
component
13
solvent
33
size
53
component
14
less
54
fixed
15
more
55
physical
16
immiscible
56
chemical
17
mix
57
new
18
mix
58
vapour
19
not easily
59
barrier
20
not easily
60
pure
Exploring Mixtures and Their Separation MCQs
🔹 Part 1: Questions 1–40
A mixture is a: A. Chemical combination B. Physical combination C. Compound D. Element
Components of a mixture: A. Lose properties B. Retain properties C. React D. Change completely
Mixtures have: A. Fixed composition B. Variable composition C. No composition D. Equal composition
Which is homogeneous? A. Sand + water B. Salt solution C. Oil + water D. Soil
Which is heterogeneous? A. Air B. Sugar solution C. Oil + water D. Vinegar
Air is a: A. Compound B. Element C. Mixture D. Solid
Pure substance: A. Milk B. Soil C. Distilled water D. Air
Milk is a: A. Compound B. Mixture C. Element D. Gas
Soil is: A. Homogeneous B. Heterogeneous C. Compound D. Element
A solution is: A. Heterogeneous B. Homogeneous C. Solid D. Gas
Solute is: A. Dissolves B. Gets dissolved C. Both D. None
Solvent is: A. Dissolves solute B. Gets dissolved C. Solid D. Gas
Salt in water is: A. Solvent B. Solute C. Residue D. Filtrate
Water in salt solution is: A. Solute B. Solvent C. Residue D. Gas
Oxygen in water is: A. Solid-liquid B. Gas-liquid C. Liquid-liquid D. Gas-gas
Alcohol + water is: A. Heterogeneous B. Homogeneous C. Solid D. Gas
A dilute solution has: A. More solute B. Less solute C. No solvent D. Only solid
Concentrated solution has: A. Less solute B. More solute C. Only solvent D. Only solute
Which is not a mixture? A. Air B. Salt solution C. Distilled water D. Milk
Compound has: A. Variable composition B. Fixed composition C. Easy separation D. Physical change
Mixtures are separated by: A. Chemical methods B. Physical methods C. Nuclear methods D. None
Visible components are in: A. Solution B. Homogeneous C. Heterogeneous D. Compound
Homogeneous mixture has: A. Visible parts B. Invisible parts C. Only solids D. Only gases
Example of solution: A. Sand + water B. Salt water C. Soil D. Oil + water
Oil and water are: A. Miscible B. Immiscible C. Soluble D. Same
Miscible liquids: A. Do not mix B. Mix completely C. Form solids D. Evaporate
Insoluble substance: A. Dissolves B. Does not dissolve C. Reacts D. Boils
Example of heterogeneous: A. Vinegar B. Air C. Soil D. Sugar solution
Example of homogeneous: A. Sand + water B. Oil + water C. Salt solution D. Soil
Solution components can be: A. Solid only B. Liquid only C. Any state D. Gas only
Suspension is: A. Clear solution B. Settling mixture C. Pure substance D. Gas
Colloid has particles that: A. Settle quickly B. Do not settle easily C. Dissolve fully D. Evaporate
Tyndall effect is shown by: A. True solution B. Colloid C. Compound D. Element
True solution is: A. Transparent B. Opaque C. Visible particles D. Settling
Particle size is smallest in: A. Suspension B. Colloid C. Solution D. Mixture
Which settles on standing? A. Solution B. Suspension C. Colloid D. Gas
Which cannot be filtered? A. Suspension B. Colloid C. Solution D. Sand
Brownian motion is seen in: A. Solids B. Colloids C. Compounds D. Elements
Milk is an example of: A. Solution B. Colloid C. Suspension D. Compound
Fog is: A. Gas in gas B. Liquid in gas C. Solid in liquid D. Gas in liquid
🔹 Part 2: Questions 41–80
Handpicking is used for: A. Liquids B. Large impurities C. Gases D. Fine particles
Sieving separates by: A. Size B. Color C. Density D. Shape
Winnowing uses: A. Water B. Wind C. Heat D. Magnet
Winnowing separates: A. Liquids B. Heavy-light solids C. Gases D. Solutions
Magnetic separation uses: A. Heat B. Magnet C. Water D. Air
Iron + sand separated by: A. Filtration B. Magnet C. Evaporation D. Funnel
Sedimentation is: A. Heating B. Settling C. Filtering D. Boiling
Decantation is: A. Filtering B. Pouring liquid C. Mixing D. Cooling
Filtration separates: A. Liquids B. Insoluble solids C. Gases D. Heat
Residue is: A. Liquid B. Solid left C. Gas D. Vapor
Filtrate is: A. Solid B. Liquid passed C. Gas D. Residue
Evaporation is: A. Gas to liquid B. Liquid to gas C. Solid to gas D. Gas to solid
Evaporation used for: A. Mixing B. Getting solid C. Cooling only D. Filtering
Condensation is: A. Liquid to gas B. Gas to liquid C. Solid to liquid D. None
Distillation is: A. Filtration B. Boiling separation C. Sieving D. Handpicking
Distillation works on: A. Density B. Boiling point C. Size D. Color
Separating funnel used for: A. Solids B. Immiscible liquids C. Gases D. Solutions
Oil + water separated by: A. Filter B. Funnel C. Magnet D. Sieve
Tea leaves removed by: A. Evaporation B. Filtration C. Sieving D. Winnowing
Salt from water by: A. Filtration B. Evaporation C. Winnowing D. Sieving
Husk from grain: A. Sieving B. Winnowing C. Filtration D. Magnet
Flour and bran: A. Sieving B. Evaporation C. Filtration D. Funnel
Muddy water cleaned by: A. Filtration B. Winnowing C. Magnet D. Handpicking
Magnetic method works on: A. Size B. Magnetism C. Density D. Heat
Sedimentation depends on: A. Density B. Color C. Size D. Heat
Winnowing depends on: A. Density B. Heat C. Color D. Shape
Filtration uses: A. Magnet B. Filter paper C. Wind D. Heat
Evaporation needs: A. Cooling B. Heating C. Magnet D. Pressure
Distillation includes: A. Evaporation + condensation B. Filtration C. Sieving D. Mixing
Separating funnel works due to: A. Density difference B. Heat C. Size D. Color
Best method for sand + water: A. Filtration B. Winnowing C. Magnet D. Evaporation
Iron from sand: A. Filter B. Magnet C. Funnel D. Heat
Alcohol + water separated by: A. Filtration B. Distillation C. Sieving D. Winnowing
Oil + water best method: A. Filtration B. Funnel C. Evaporation D. Magnet
Salt + sand separated by: A. Magnet B. Dissolve + filter C. Winnowing D. Funnel
Air components separated by: A. Distillation B. Filtration C. Sieving D. Winnowing
Large stones removed by: A. Handpicking B. Filtration C. Evaporation D. Funnel
Fine particles separated by: A. Handpicking B. Filtration C. Winnowing D. Magnet
Two liquids mixing completely are: A. Immiscible B. Miscible C. Insoluble D. Solid
Removal of impurities is called: A. Separation B. Mixing C. Reaction D. Cooling
🔹 Part 3: Questions 81–120
Assertion: Mixtures have variable composition Reason: Components are not chemically combined A. Both true & reason correct B. Both true but reason wrong C. A true, R false D. Both false
Assertion: Oil and water form layers Reason: They are immiscible A. Both true & correct B. Both true but wrong reason C. A true, R false D. Both false
Assertion: Filtration removes dissolved solids Reason: Filter paper blocks solids A. Both true B. A false, R true C. Both false D. A true, R false
Assertion: Evaporation leaves solid Reason: Liquid changes to vapor A. Both true & correct B. Both true wrong reason C. A true, R false D. Both false
Assertion: Distillation separates liquids Reason: Based on boiling point A. Both true & correct B. Both true wrong reason C. A true, R false D. Both false
Assertion: Winnowing uses wind Reason: Based on density A. Both true & correct B. Both true wrong reason C. A true, R false D. Both false
Assertion: Magnetic separation removes iron Reason: Iron is magnetic A. Both true & correct B. Both true wrong reason C. A true, R false D. Both false
Assertion: Sedimentation settles particles Reason: Due to gravity A. Both true & correct B. Both true wrong reason C. A true, R false D. Both false
Assertion: Funnel separates oil and water Reason: Density difference A. Both true & correct B. Both true wrong reason C. A true, R false D. Both false
Assertion: Mixtures cannot be separated Reason: They are compounds A. Both true B. Both false C. A true, R false D. A false, R true
Assertion: Solutions are homogeneous Reason: Uniform composition A. Both true & correct B. Both true wrong reason C. A true, R false D. Both false
Assertion: Milk is pure Reason: It has uniform composition A. Both true B. A false, R true C. Both false D. A true, R false
Assertion: Air is mixture Reason: Many gases present A. Both true & correct B. Both true wrong reason C. A true, R false D. Both false
Assertion: Filtration uses heat Reason: Solid evaporates A. Both true B. Both false C. A true, R false D. A false, R true
Assertion: Evaporation needs heat Reason: Liquid turns gas A. Both true & correct B. Both true wrong reason C. A true, R false D. Both false
Assertion: Distillation includes condensation Reason: Vapor cools A. Both true & correct B. Both true wrong reason C. A true, R false D. Both false
Assertion: Sieving uses size difference Reason: Smaller particles pass A. Both true & correct B. Both true wrong reason C. A true, R false D. Both false
Assertion: Funnel used for miscible liquids Reason: They mix A. Both true B. A false, R true C. Both false D. A true, R false
Assertion: Decantation follows sedimentation Reason: Liquid poured off A. Both true & correct B. Both true wrong reason C. A true, R false D. Both false
Assertion: Homogeneous mixtures are uniform Reason: Same composition throughout A. Both true & correct B. Both true wrong reason C. A true, R false D. Both false
Which shows Tyndall effect? A. Solution B. Colloid C. Compound D. Element
Which does not scatter light? A. Solution B. Colloid C. Suspension D. Smoke
Example of aerosol: A. Fog B. Milk C. Salt water D. Soil
Foam is: A. Gas in liquid B. Liquid in gas C. Solid in liquid D. Gas in solid
Emulsion is: A. Liquid in liquid B. Solid in liquid C. Gas in liquid D. Gas in solid
Which is stable? A. Suspension B. Solution C. Large particles D. Sand
Which settles on standing? A. Solution B. Suspension C. Colloid D. Air
Which is filtered easily? A. Solution B. Suspension C. Colloid D. Gas
Which is transparent? A. Solution B. Suspension C. Soil D. Mud
Which is opaque? A. Solution B. Suspension C. Salt water D. Air
True solution particle size is: A. Large B. Medium C. Very small D. Visible
Colloid particle size is: A. Very small B. Medium C. Large D. Visible
Suspension particle size is: A. Small B. Medium C. Large D. Invisible
Which shows Brownian motion? A. Solution B. Colloid C. Solid D. Compound
Best method for muddy water: A. Filtration B. Winnowing C. Magnet D. Funnel
Which method uses both heat and cooling? A. Distillation B. Filtration C. Sieving D. Winnowing
Which is immiscible pair? A. Alcohol + water B. Oil + water C. Sugar + water D. Salt + water
Which is miscible pair? A. Oil + water B. Alcohol + water C. Sand + water D. Soil + water
Which is a pure substance? A. Air B. Soil C. Distilled water D. Milk
Which is a mixture? A. Oxygen B. Hydrogen C. Air D. Gold