Chapter 2: Is Matter Around Us Pure?
2.1 What is a Mixture?
Mixtures are constituted by more than one kind of pure form of matter. A pure substance consists of a single type of particle.
Homogeneous Mixtures
Uniform composition throughout. Example: Salt in water, Sugar in water.
Heterogeneous Mixtures
Physically distinct parts and non-uniform compositions. Example: Oil in water, Sand and salt.
2.2 What is a Solution?
A solution is a homogeneous mixture of two or more substances. It consists of a solvent (major part) and a solute (component being dissolved).
Tincture of Iodine
A solution of iodine in alcohol where iodine is the solute and alcohol is the solvent.
2.3 Concentration of a Solution
Key formulas for measuring concentration:
- Mass by mass percentage: (Mass of solute / Mass of solution) × 100
- Mass by volume percentage: (Mass of solute / Volume of solution) × 100
2.4 Suspensions and Colloids
| Property | Solution | Suspension | Colloid |
|---|---|---|---|
| Type | Homogeneous | Heterogeneous | Heterogeneous |
| Particle Size | < 1 nm | > 1000 nm | 1 nm - 1000 nm |
| Tyndall Effect | No | Yes | Yes |
| Stability | Stable | Unstable | Stable |
Physical vs Chemical Changes
Physical Change: No new substance is formed (e.g., melting of ice).
Chemical Change: New substances with different properties are formed (e.g., burning of wood).