0Class 8 Science – Particulate Nature of Matter & Elements and Compounds
1. Particulate Nature of Matter
Introduction
-
All matter is made up of tiny particles (atoms and molecules).
-
Particles are too small to be seen with eyes.
-
Matter exists in three main states: solid, liquid, and gas.
Key Concepts
-
Particles are always in motion
-
Solids: Vibrate in fixed positions.
-
Liquids: Move freely but remain close.
-
Gases: Move very fast and are far apart.
-
-
Particles have spaces between them
-
Solids: Very little space → fixed shape.
-
Liquids: Some space → take shape of container.
-
Gases: Large space → fill entire container.
-
-
Particles attract each other
-
Strong in solids, moderate in liquids, weak in gases.
-
Implications of Particulate Nature
-
Explains diffusion, expansion on heating, compression of gases, and changes of state.
-
Helps understand melting, boiling, evaporation, and condensation.
2. Elements
Introduction
-
Elements are pure substances made of only one type of atom.
-
Cannot be broken into simpler substances by chemical means.
Characteristics
-
Each element has unique properties.
-
Examples: Hydrogen, Oxygen, Iron, Carbon.
-
Represented by symbols (H, O, Fe, C).
Uses
-
Iron: Construction and machinery.
-
Oxygen: Breathing and medical use.
-
Carbon: Fuel, pencils, and steel manufacturing.
3. Compounds
Introduction
-
Compounds are substances made of two or more elements chemically combined in a fixed ratio.
-
Properties of a compound are different from its constituent elements.
Characteristics
-
Can be broken down into elements by chemical reactions.
-
Have definite composition.
-
Examples: Water (H₂O), Carbon dioxide (CO₂), Sodium chloride (NaCl).
Uses
-
Water: Drinking and agriculture.
-
Carbon dioxide: Carbonated drinks, fire extinguishers.
-
Salt: Food and preservation.
4. Key Differences Between Elements and Compounds
| Feature | Element | Compound |
|---|---|---|
| Composition | One type of atom | Two or more elements |
| Can be broken down | No | Yes, by chemical means |
| Properties | Unique to element | Different from constituent elements |
| Examples | Oxygen, Iron, Carbon | Water, Salt, Carbon dioxide |
5. Key Points to Remember
-
Matter is made of tiny particles with spaces and motion.
-
Solids, liquids, and gases differ in particle arrangement, motion, and attraction.
-
Elements: Pure substances, single type of atom, cannot be broken down.
-
Compounds: Chemically combined elements, can be separated chemically.
-
Understanding particulate nature explains physical and chemical behavior of matter.
