1. Pure Substances vs Mixtures
A pure substance consists of a single type of particles. A mixture contains more than one
kind of pure form of matter. Mixtures can be homogeneous (uniform composition) or
heterogeneous (non-uniform composition).
2. Solutions, Suspensions, and Colloids
- Solution: A homogeneous mixture of two or more substances. Particles
are smaller than 1nm. It does not scatter light.
- Suspension: A heterogeneous mixture in which the solute particles do
not dissolve but remain suspended. Particles are visible to the naked eye.
- Colloid: A heterogeneous mixture where particle size is intermediate
(1nm - 1000nm). It scatters a beam of light (Tyndall Effect).
3. Separation Techniques
- Evaporation: To separate volatile component from non-volatile solute.
- Centrifugation: To separate denser particles from lighter particles
when spun rapidly.
- Chromatography: To separate solutes that dissolve in the same solvent.
- Distillation: To separate miscible liquids that boil without
decomposition and have sufficient difference in boiling points.
4. Physical and Chemical Changes
Physical changes do not produce new substances (e.g., melting ice). Chemical changes result
in the formation of new substances with different properties (e.g., burning paper).