Question 4
Explain the following, giving examples.
(a) Saturated solution
(b) Pure substance
(c) Colloid
(d) Suspension
(a) Saturated solution — A saturated solution is one which cannot dissolve more of the solute at a given temperature.
Example: Excess carbon leaves off as bubbles from a carbonated water solution saturated with carbon.
(b) Pure substance — A substance is said to be pure when it comprises of only one kind of molecules or atoms.
Example: Sulphur, diamonds etc.
(c) Colloid — A colloid is a heterogeneous mixture in which the size of solute particles is intermediate between true solution and suspension and it shows tyndall effect.
Examples: Soap solution, starch solution, milk.
(d) Suspension — It is a heterogeneous mixture in which the small particles of a solid are spread throughout a liquid without dissolving in it. Particles of a suspension are visible to the naked eye.
Examples: Chalk water mixture, muddy water etc.
Chapter 2: Is Matter Around Us Pure — Quick Reference
Quick Revision Points
- Pure substances: fixed composition (elements + compounds). Mixtures: variable composition
- Solution (< 1 nm, transparent), Colloid (1-100 nm, Tyndall effect), Suspension (> 100 nm, settles)
- Concentration = (mass of solute / mass of solution) × 100
- Separation: evaporation, centrifugation, chromatography, distillation, sublimation, crystallisation, separating funnel
- Elements: metals, non-metals, metalloids. Compounds: fixed ratio, chemical separation
- Tyndall effect: scattering of light by colloidal particles (milk, fog, smoke)
- Read the detailed chapter notes for complete coverage of all NCERT topics.
- Practice all NCERT in-text and back exercise questions — they are frequently asked in exams.
- Focus on comparison tables, diagrams, and definitions — these are high-scoring areas.
- For numericals (if applicable), practice at least 20 problems of varying difficulty.
- Refer to the practice question bank (200+ questions) for thorough preparation.
- Detailed Notes: ch02-is-matter-around-us-pure.html
- Practice Questions: 100+ questions with answers in 05-practice-questions/
- Chapter Test: 30-mark test paper in 06-tests/chapter-tests-30marks/
- Formula Sheet: Complete formula reference in 03-teacher-aid/formula-sheet.html