Is Matter Around Us Pure?

Chapter 2 – Is Matter Around Us Pure? (Simple Notes)

1. Pure Substances and Mixtures

Pure Substance:

A substance made of only one kind of particle.

Example: Water (H₂O), Gold (Au), Oxygen (O₂)

Mixture:

A combination of two or more substances mixed together, not chemically combined.

Example: Air, Salt water, Milk

2. Types of Mixtures

A. Homogeneous Mixture:

Looks the same throughout

Particles are not visible

Example: Salt in water, Sugar solution, Air

B. Heterogeneous Mixture:

Does not look the same throughout

Particles can be seen

Example: Sand in water, Oil in water

3. Solution

A solution is a homogeneous mixture.

Made of two parts:

Solute – the substance that dissolves (e.g. salt)

Solvent – the substance that dissolves the solute (e.g. water)

Properties of solutions:

Clear and transparent

Cannot be separated by filtration

Do not scatter light

4. Suspension

A suspension is a heterogeneous mixture where solid particles are spread in a liquid or gas.

Example: Muddy water

Properties:

Particles are visible

Settle down over time

Can be separated by filtration

Scatter the light

5. Colloid

A colloid is a mixture where particles are smaller than in suspensions but bigger than in solutions.

Example: Milk, Smoke, Fog

Properties:

Looks uniform but is actually heterogeneous

Particles do not settle

Cannot be separated by filtration

Show Tyndall effect (scatter light)

6. Methods of Separation

Filtration – separates insoluble solids

Evaporation – removes liquid from solution

Centrifugation – separates heavier particles using spinning

Decantation – pouring off the top layer

Sublimation – separates substances like camphor

Distillation – separates liquids with different boiling points

Chromatography – separates colors or dyes

7. Elements, Compounds and Mixtures

Type What it is Examples

Element Only one type of atom Iron, Oxygen

Compound Two or more elements chemically combined Water, CO₂

Mixture Two or more substances not chemically combined Air, Saltwater

8. Physical and Chemical Changes

Physical Change Chemical Change

No new substance New substance formed

Reversibl

e Irreversible

Example: Melting ice Example: Burning paper