Introduction
Matter around us is usually not pure. Most substances we see are mixtures of two or more components. A pure substance contains only one type of particle and has fixed properties.
Pure Substances
- Contain only one kind of particle.
- Have fixed composition and properties.
- Types of pure substances:
- Elements – Made of only one type of atom.
- Example: Hydrogen, Oxygen, Iron.
- Compounds – Made of two or more elements chemically combined.
- Example: Water (H₂O), Salt (NaCl).
- Elements – Made of only one type of atom.
Mixtures
- Combination of two or more substances mixed physically.
- Components can be separated by physical methods.
- Properties of components are retained.
Types of Mixtures
1. Homogeneous Mixture
- Uniform composition throughout.
- Components are not visible separately.
- Example: Salt solution, air.
2. Heterogeneous Mixture
- Non-uniform composition.
- Components are visible.
- Example: Sand and water, oil and water.
Solutions
A solution is a homogeneous mixture.
Components of a Solution
- Solvent: Substance that dissolves other substances (e.g., water).
- Solute: Substance that gets dissolved (e.g., salt, sugar).
Types of Solutions
- Solid in liquid: Salt in water.
- Liquid in liquid: Alcohol in water.
- Gas in liquid: Carbon dioxide in soda.
- Gas in gas: Air.
Concentration of a Solution
Shows how much solute is dissolved in a solvent.
- Concentrated solution: More solute.
- Dilute solution: Less solute.
Separating the Components of a Mixture
Different methods are used based on the nature of the mixture:
- Evaporation: Separating salt from water.
- Filtration: Separating sand from water.
- Distillation: Separating liquids with different boiling points.
- Chromatography: Separating colors in ink.
- Centrifugation: Separating cream from milk.
Physical and Chemical Changes
- Physical Change: No new substance formed (e.g., melting ice).
- Chemical Change: New substance formed (e.g., rusting of iron).
Quick Short Q&A (Most Possible)
| Question | Short Answer |
|---|---|
| Is all matter pure? | No, most matter is impure. |
| What is a pure substance? | Substance with only one type of particle. |
| Examples of elements? | Hydrogen, Oxygen, Iron. |
| Examples of compounds? | Water, Salt. |
| What is a mixture? | Physical combination of substances. |
| Homogeneous mixture? | Uniform composition. |
| Heterogeneous mixture? | Non-uniform composition. |
| What is a solution? | Homogeneous mixture. |
| Solute definition? | Substance that dissolves. |
| Solvent definition? | Substance that dissolves solute. |
| Method to separate salt from water? | Evaporation. |
| Filtration is used for? | Solid-liquid separation. |
| Physical vs chemical change? | Physical: no new substance, Chemical: new substance formed. |