Nature of Matter
Quick Notes:
- Matter is anything that has mass and occupies space.
- Exists in three states: solid, liquid, gas.
- Solids: Fixed shape and volume, tightly packed particles, incompressible.
- Liquids: Fixed volume, no fixed shape, flow easily, low compressibility.
- Gases: No fixed shape or volume, compressible, particles far apart.
- Changes of state:
- Melting: Solid → Liquid (heating)
- Freezing: Liquid → Solid (cooling)
- Boiling: Liquid → Gas (heating)
- Condensation: Gas → Liquid (cooling)
- Sublimation: Solid ↔ Gas (e.g. iodine, camphor)
- Classification by composition:
- Pure Substances: Constant composition (Elements or Compounds)
- Mixtures: Variable composition (Homogeneous or Heterogeneous)
- Mixtures can be separated by physical methods; compounds cannot.
Full Notes:
1.2.1 States of Matter
The Three States
Matter commonly exists in three physical states under ordinary conditions:
Solids: Have definite volume and definite shape. Tightly packed particles, cannot be compressed, do not flow.
Liquids: Have definite volume and do not have definite shape. Flow easily, take shape of container, low compressibility.
Gases: No definite volume nor definite shape. Expand freely, fill container, highly compressible.
| State | Shape | Volume | Compressibility | Particle Arrangement |
|---|---|---|---|---|
| Solid | Fixed | Fixed | Negligible | Closely packed, ordered |
| Liquid | Variable | Fixed | Low | Loosely packed, fluid |
| Gas | Variable | Variable | High | Widely spaced, free |
Interconversion of States
These changes are physical – no new substance is formed – and usually reversible.
| Change | Transition | Cause |
|---|---|---|
| Melting | Solid → Liquid | Heating |
| Freezing | Liquid → Solid | Cooling |
| Vaporisation (Boiling and Evaporating) | Liquid → Gas | Heating |
| Condensation | Gas → Liquid | Cooling |
| Sublimation | Solid ↔ Gas | Heating / Cooling |
Question: Which process converts water vapour to water?
- A. Freezing
- B. Boiling
- C. Condensation
- D. Sublimation
Answer: C – Condensation
Use visual memory here: associate state changes with common daily examples — steam condensing on mirror, ice melting in hand, naphthalene balls shrinking over time.
1.2.2 Classification of Matter
Matter is also categorised based on composition, leading to a chemical understanding of substances.
Pure Substances
Pure substances have a definite composition and distinct chemical properties. Cannot be separated by physical means.
Elements
Made of only one kind of atom. Cannot be broken down chemically. May exist as atoms (He) or molecules (O2).
Example: Copper solid is made up of only one type of atom, meaning it is an element.
Compounds
Chemically combined in fixed ratio. Have properties different from constituent elements. Can be broken down only chemically.
Example: Water is made up of molecules of hydrogen and oxygen bonded together, meaning it is a compound.
| Type | Example | Notes |
|---|---|---|
| Element | Copper (Cu), Nitrogen (N2) | Simplest form, one type of atom |
| Compound | Water (H2O), CO2 | Fixed ratio, chemically bonded |
Mixtures
Mixtures contain two or more substances mixed physically. There are two types of mixture, homogeneous and heterogeneous.
Homogeneous Mixtures
- Uniform throughout
- Also called solutions
- Cannot see components separately
Example: Water and ethanol mix uniformly to create a homogeneous mixture.
Common Examples: Air, vinegar, salt water
Heterogeneous Mixtures
- Non-uniform
- components visible
- Particles may settle or be distinct
Example: Water and oil don’t mix uniformly and create a heterogeneous mixture with two layers of liquid.
Question: Which of the following is a compound?
- A. Air
- B. Brass
- C. Glucose
- D. Soil
Answer: C – Glucose
Explanation: Fixed ratio of C, H, O; chemically bonded.
If it can be separated easily (by filtration, evaporation, etc.), it’s likely a mixture. If not, it’s probably a compound.
Summary
- Matter exists mainly as solids, liquids, and gases with distinct particle arrangements and properties.
- Changes of state like melting, freezing, and condensation are physical and reversible.
- Pure substances have fixed composition; mixtures have variable composition.
- Homogeneous mixtures are uniform; heterogeneous mixtures are not.
- Elements contain one type of atom; compounds have atoms chemically bonded in fixed ratios.