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WEEK 2
Topic: PARTICULATE NATURE OF MATTER
CONTENTS:
- Physical and chemical changes
- Elements and their symbols.
- Atoms, molecules, atomicity
- Dalton’s atomic theory
PERIOD 1: PHYSICAL AND CHEMICAL CHANGES
PHYSICAL CHANGES:
DEFINITION: A Physical change is one which is easily reversed and in which no new substances are formed.
Examples:
- Melting of solids to liquids.
- Freezing of liquids to solids.
- Vaporization of liquids to gases.
- Liquefaction of gases to liquids.
- Sublimation of solids to vapour.
CHEMICAL CHANGE:
DEFINITION: A chemical change is one which is not easily reversed andin which a new substance is formed.
Examples:
- Burning of substances.
- Dissolution of metals and limestone in acids.
- Chemical decomposition – like digestion of food.
- Rusting of iron.
- Charring of sugar.
- Dissolution of metals in acids.
DIFFERENCES BETWEEN PHYSICAL AND CHEMICAL CHANGE
PHYSICAL CHANGE | CHEMICAL CHANGE |
Easily reversible | Not easily reversible |
No new substance is formed | New substance is formed |
No change is mass. | There is a noticeable change in mass. |
Not accompanied by heat | usually accompanied by heat change. |
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