These are selected revision notes and practice questions. No original exam-year or paper references have been verified; these questions are not presented as authenticated past papers. Use your current textbook and teacher guidance for complete coverage.
| Property | True Solution | Colloid | Suspension |
|---|---|---|---|
| Particle Size | $< 1\text{ nm}$ ($10^{-9}\text{ m}$) | $1\text{ nm} - 1000\text{ nm}$ | $> 1000\text{ nm}$ |
| Appearance | Homogeneous & Transparent | Heterogeneous look, homogeneous appearance | Heterogeneous & Opaque |
| Tyndall Effect | Does NOT scatter light | SCATTERS light prominently | Scatters light until settled |
| Stability | Stable (particles don't settle) | Quite stable | Unstable (settles down) |
| Separation | Cannot be filtered | Centrifugation required | Can be filtered easily |
The tiny water droplets and dust particles in mist act as colloidal particles that scatter the path of light, making the beam visible. This optical scattering phenomenon is called the Tyndall Effect.
Answer: Physical changes involve no new substance formation and are reversible (e.g. melting of ice, cutting of wood). Chemical changes produce new substances with entirely different properties and are irreversible (e.g. rusting of iron, burning of paper).