Chapter 5: Exploring Mixtures and their Separation
Welcome to your interactive science laboratory! Explore the world of mixtures through virtual experiments, animations, calculations, discoveries and challenges.
Complete each lesson as you learn.
What Are Mixtures?
Look around you. The air you breathe, the milk you drink and the soil beneath your feet are all examples of mixtures.
A mixture contains two or more substances physically combined. Its components may be present in different proportions.
Homogeneous Mixture
Composition is uniform throughout.
Examples: Salt solution, sugar solution, vinegar and brass.
Imagine taking two sips of well-mixed lemonade. Both should taste equally sweet.
Heterogeneous Mixture
Composition is not uniform throughout.
Examples: Sand and water, oil and water, smoke and muddy water.
You can often distinguish different components.
🧪 Virtual Lab: Mix and Observe
Choose a mixture and watch how it behaves.
🧠 Quick Check
Which is a homogeneous mixture?
Solutions: Solute and Solvent
A solution is a homogeneous mixture of two or more substances.
Solute
The substance that dissolves.
Example: Sugar in sugar-water solution.
Solvent
The substance that dissolves the solute.
Example: Water in sugar-water solution.
Solutions are not always solid-in-liquid. Carbon dioxide dissolved in soda is a gas-in-liquid solution. Brass is a solid alloy that forms a homogeneous mixture.
Concept Check
In sugar solution, which substance is the solvent?
Concentration of Solutions
Why does one cup of tea taste sweeter than another? The answer may be the concentration of sugar.
Concentration tells us how much solute is present in a given quantity of solution or solvent.
Three Ways to Express Concentration
Example: 10 g salt + 90 g water gives 100 g solution.
Concentration = (10 ÷ 100) × 100 = 10% m/m.
5 g glucose in a final solution volume of 100 mL = 5% m/v.
1 mL liquid pesticide in 100 mL of final solution = 1% v/v.
🧮 Interactive Concentration Calculator
Select the concentration type and enter your values.
Unit: grams
Unit: grams
Knowledge Check
20 g salt is dissolved in 80 g water. What is the % m/m concentration?
Solubility and Saturated Solutions
Solubility is the maximum amount of a solute that dissolves in a fixed quantity of solvent at a given temperature.
A saturated solution cannot dissolve more solute at that temperature under the given conditions.
Unsaturated Solution
Can dissolve more solute at the same temperature.
Saturated Solution
Has reached its dissolving capacity at the given temperature.
For many solids, solubility increases with temperature. For gases dissolved in liquids, solubility generally decreases as temperature rises.
🌡 Virtual Solubility Experiment
Explore compound B from the NCERT solubility graph.
At 40°C, its solubility is 241 g per 100 g water. At 60°C, it is 287 g per 100 g water.
Think Like a Scientist
What generally happens to the solubility of many solids in water when temperature increases?
Crystallization
Have you seen mishri or beautiful crystals of rock salt? These are examples of crystals with ordered internal arrangements.
Crystallization is the process of forming crystals from a solution. It is useful for obtaining and purifying solids.
How Does It Work?
💎 Virtual Crystal Growth
Observe the difference between rapid and slow cooling.
Concept Check
Which cooling method generally produces larger, better-formed crystals?
Distillation
Imagine mixing acetone and water. Both liquids mix completely. How can we separate them?
Distillation involves heating a liquid mixture to produce vapour and cooling that vapour to collect liquid again.
Boiling point: approximately 56°C
Boiling point: approximately 100°C
The NCERT chapter describes simple distillation for liquids differing in boiling point by about 25°C or more. Liquids with closer boiling points generally require fractional distillation.
🔥 Interactive Distillation Demonstration
Move through the stages of the process.
Knowledge Check
What is the function of the condenser?
Paper Chromatography
Did you know that black ink may contain several coloured dyes?
Paper chromatography separates substances according to how differently they move with a solvent through paper.
🎨 Virtual Ink Separation
Start the experiment and observe the movement of coloured pigments.
Quick Check
Where should the ink spot be at the beginning?
Separating Immiscible Liquids
Oil and water do not mix. Such liquids are called immiscible liquids.
They form separate layers. Mustard oil floats on water because it is less dense.
A separating funnel separates these liquids using their difference in density.
💧 Virtual Separating Funnel
Think and Answer
Which liquid drains first from an oil-water separating funnel?
Sublimation and Alloys
Sublimation is the direct change of a solid into vapour without passing through the liquid state.
Camphor and naphthalene are examples of substances that sublime. Sand does not sublime under the conditions used in the textbook experiment.
🌫 Virtual Sublimation
Separate camphor from sand by observing the change of state.
What Are Alloys?
An alloy is a homogeneous mixture of two or more metals, or of a metal and a non-metal.
| Alloy | Main Components | Common Uses |
|---|---|---|
| Brass | Copper and zinc | Utensils, fittings and musical instruments |
| Bronze | Copper and tin | Statues and medals |
| Stainless steel | Iron with chromium and other elements | Kitchenware and equipment |
Quick Check
Which property helps separate camphor from sand?
Suspensions, Centrifugation and Coagulation
A suspension is a heterogeneous mixture in which insoluble particles remain dispersed temporarily in a medium.
Examples include muddy water and sand in water. The particles are relatively large and can settle on standing.
How Can We Separate Suspended Particles?
Allow heavier particles to settle at the bottom.
Carefully pour away the clearer liquid above the settled material.
Pass the mixture through a filter to retain insoluble particles.
Spin rapidly to separate components according to density.
Coagulation
Very fine particles may not settle easily. Adding a coagulant such as alum helps them form larger clumps that settle more readily.
Science and Society: The Paperfuge
A paperfuge is a hand-powered spinning device that can separate components of small blood samples without electricity. It demonstrates how simple scientific ideas can support healthcare in remote areas.
Concept Check
Which method uses rapid spinning?
Colloids: Between Solutions and Suspensions
Milk appears uniform, but it contains tiny droplets of fat dispersed in water. It is an example of a colloid.
Colloids have particles larger than those of true solutions but smaller than those of ordinary suspensions.
| Property | Solution | Colloid | Suspension |
|---|---|---|---|
| Nature | Homogeneous | Heterogeneous | Heterogeneous |
| Particle size | Less than 1 nm | 1–1000 nm | More than 1000 nm |
| Visible particles | No | Not individually visible to naked eye | Generally visible |
| Settling | No | Generally no | Yes, on standing |
| Ordinary filtration | Does not separate solute | Does not separate colloidal particles | Generally separates particles |
| Light scattering | No appreciable Tyndall effect | Yes | Yes |
| Example | Salt solution | Milk | Sand in water |
Dispersed Phase and Dispersion Medium
The dispersed phase consists of the tiny particles or droplets distributed through the mixture.
The dispersion medium is the substance through which those particles are distributed.
Dispersed phase: Tiny fat droplets.
Dispersion medium: Mainly water.
Emulsions
An emulsion is a colloid in which liquid droplets are dispersed in another liquid. Milk is an oil-in-water emulsion, while butter is commonly described as a water-in-oil emulsion.
Knowledge Check
Milk is best classified as which type of mixture?
The Tyndall Effect
Have you seen rays of sunlight passing through a dusty room? The path of the light becomes visible because tiny particles scatter it.
This phenomenon is called the Tyndall effect.
🔦 Virtual Light Scattering Lab
Pass a beam of light through three mixtures.
True solutions do not scatter visible light appreciably, while colloids and suspensions do.
Quick Check
What causes the Tyndall effect?
Connect Everything: Revision Lab
Science becomes easier when you connect each separation method with the physical property it uses.
| Method | Property Used | Example |
|---|---|---|
| Filtration | Particle size | Sand from water |
| Evaporation | Volatility | Salt from seawater |
| Crystallization | Solubility differences | Copper sulfate crystals |
| Distillation | Boiling point difference | Acetone and water |
| Fractional distillation | Relatively close boiling points | Petroleum fractions |
| Chromatography | Different movement rates | Ink pigments |
| Separating funnel | Density and immiscibility | Oil and water |
| Sublimation | Direct solid-to-vapour transition | Camphor and sand |
| Centrifugation | Density differences during spinning | Blood components |
| Coagulation | Clumping of fine particles | Clarifying muddy water |
🃏 Interactive Revision Flashcards
Click the card to reveal the meaning. Use Next Card to revise another concept.
