🔹 I. What is a Pure Substance?

• A pure substance contains only one type of particle.
• It has uniform composition and fixed properties (melting point, boiling point, etc.).

🔸 Examples:

• Pure Substance: Distilled water, pure gold, oxygen
• Impure Substance / Mixture: Air, tap water, milk

🔹 II. Types of Matter Based on Purity

🔹 III. Pure Substances

1. Elements:

• Cannot be broken down into simpler substances.
• Made of only one kind of atom.

Types:

• Metals: e.g., Iron, Copper (lustrous, conduct electricity)
• Non-metals: e.g., Oxygen, Sulphur (non-lustrous, poor conductors)
• Metalloids: e.g., Silicon (properties of both)

2. Compounds:

• Formed when two or more elements chemically combine in a fixed ratio.
• Properties of compound are different from its constituent elements.
• Example: Water (H₂O), CO₂, NaCl

🔹 IV. Mixtures

• Made of two or more substances (elements or compounds) physically combined.
• Can be separated by physical methods.
• Do not have fixed composition.

🔸 Types of Mixtures:

🔹 V. Solutions

1. Definition:

• A homogeneous mixture of two or more substances.

2. Components:

• Solute: The substance that dissolves (lesser quantity)
• Solvent: The substance that dissolves the solute (larger quantity)

Example: In sugar solution, sugar is solute, water is solvent.

3. Properties of a Solution:

• Clear and transparent
• Does not scatter light
• Solute particles cannot be separated by filtration
• Stable (no settling)

4. Concentration of Solution:

• Dilute Solution: Small amount of solute
• Concentrated Solution: Large amount of solute

Formula:

Concentration=Mass of soluteMass of solution×100Concentration=Mass of solutionMass of solute​×100

🔹 VI. Suspensions

• A heterogeneous mixture with visible particles.
• Particles settle when left undisturbed.

Properties:

• Particles are visible
• Can be separated by filtration
• Scatters light (Tyndall effect)
• Unstable mixture

Examples: Chalk in water, muddy water

🔹 VII. Colloids (Colloidal Solutions)

• A mixture where particles are intermediate in size (between solutions and suspensions).
• Heterogeneous, but appears homogeneous to the eye.

Examples: Milk, starch solution, fog, smoke

Types of Colloids (based on dispersion medium & phase):

🔹 VIII. Separating Components of Mixtures

🔹 IX. Tyndall Effect

• The scattering of light by colloidal particles.
• Seen in: Colloids and suspensions (not true solutions)
• Example: Beam of sunlight entering a dark room through curtains.

🔹 X. Differences Summary Table

🔹 XI. NCERT Questions Highlights

Q1: Classify the following as homogeneous or heterogeneous:

• Soda water – Homogeneous
• Wood – Heterogeneous
• Air – Homogeneous
• Soil – Heterogeneous

Q2: Why is air considered a mixture?

• Because it contains various gases physically mixed (N₂, O₂, CO₂), not chemically combined.

🔹 XII. Real-Life Examples

• Homogeneous mixtures: Saltwater, vinegar, air
• Heterogeneous mixtures: Salad, concrete, granite
• Colloids: Toothpaste, fog, milk
• Suspensions: Paint, muddy water

🔹 XIII. Mind Map

IS MATTER AROUND US PURE?

|

————–               —————

|                                     |

Pure Substances                   Mixtures

(Elements, Compounds)             (Homogeneous, Heterogeneous)

|

————————————-

|                                   |

Solution                            Non-Solution

(saltwater, air)              (Suspensions, Colloids)