What is the difference between a colloid and a suspension?

Colloid: particle size 1–1000 nm, stable (does not settle), shows Tyndall effect (e.g., milk, fog). Suspension: particle size > 1000 nm, unstable (settles on standing), heterogeneous (e.g., muddy water). Both are heterogeneous mixtures but differ in particle size and stability.

What is the Tyndall effect?

The Tyndall effect is the scattering of a beam of light by colloidal particles, making the path of light visible. It is NOT shown by true solutions (particles too small). Examples: fog scattering car headlights, sunlight through holes in curtains making dust visible. It is used to distinguish colloids from true solutions.

How do you separate a mixture of salt and water?

Evaporation: heat the salt water until water evaporates, leaving salt crystals behind. For purer salt, use crystallisation (slow evaporation). Distillation can be used if you want to collect both water and salt separately — the water condenses and is collected, leaving salt behind.

Mixtures and Solutions

Is Matter Around Us Pure • Class 9 Science • NCERT • CBSE

A mixture is a combination of two or more substances mixed together but not chemically combined. Mixtures can be homogeneous (like salt water) or heterogeneous (like sand and water). Solutions are homogeneous mixtures with a solute dissolved in a solvent.

Key Formulas

Concentration = (Mass of solute / Volume of solution) × 100
True solution: particle size < 1 nm
Colloid: particle size 1–1000 nm
Suspension: particle size > 1000 nm

Frequently Asked Questions

What is the difference between a colloid and a suspension?: Colloid: particle size 1–1000 nm, stable (does not settle), shows Tyndall effect (e.g., milk, fog). Suspension: particle size > 1000 nm, unstable (settles on standing), heterogeneous (e.g., muddy water). Both are heterogeneous mixtures but differ in particle size and stability.
What is the Tyndall effect?: The Tyndall effect is the scattering of a beam of light by colloidal particles, making the path of light visible. It is NOT shown by true solutions (particles too small). Examples: fog scattering car headlights, sunlight through holes in curtains making dust visible. It is used to distinguish colloids from true solutions.
How do you separate a mixture of salt and water?: Evaporation: heat the salt water until water evaporates, leaving salt crystals behind. For purer salt, use crystallisation (slow evaporation). Distillation can be used if you want to collect both water and salt separately — the water condenses and is collected, leaving salt behind.

Study With GyanAI

GyanAI's AI tutor can answer any question about this topic instantly. Try GyanAI free for step-by-step NCERT solutions aligned with the CBSE curriculum.