Changes and Particle Theory

• What is the colour of these solids ? colourless

Physical Properties

• Colour is one of the physical properties of a substance.

• Can you tell me some other physical properties of a substance ?

• State• Melting point• Boiling point• Taste

Table salt Water Chlorine

colourcolour colourless colourless Pale green

StateState Solid Liquid Gas

Melting Melting pointpoint

808C0C -101C

• Physical change is a change in which no new substances are formed.

Water water vapour

Examples of physical change

• Dissolving salt in water• Water turns into ice• Ice-cream changes into liquid• Evaporation• Boiling • Condensation• Freezing• Melting• Sublimation

A change is a change in which one or more new substances are formed.

Burning always is a chemical change.

Wood carbon dioxide

Decide whether each of the following is physical or

chemical change:

• Breaking a glass cup

• Burning coal in air

• Frying an egg

• Evaporating salt solution to dryness

Particle theory of Matter

• Iodine(碘 ) particles leave the solid and mix with the alcohol particles.

Three States of Matter

• Solids,

• Liquids,

• Gases

Which of following is a chemical property ?

A. Tastes like alcohol.

B. Burns in air.

C. Mixes in all proportions with water.

D. Colourless.