(2.3) Chemical Reaction Evidence

(p142-143)

Chemical Reaction

In a chemical reaction new substances are always formed.

Can you identify a chemical reaction that you have seen or used today?

Evidence of Chemical Reactions

When a chemical reaction occurs four types of observations can be made.

Can you name some?1.2.3. 4.

Evidence of Chemical Reactions – 4 Types

1. ENERGY CHANGE A temperature

change (increase or decrease)

Light is produced Electricity is

produced

Evidence of Chemical Reactions – 4 Types

2. GAS IS FORMED Bubbles form in a

liquid Presence of an odour

Evidence of Chemical Reactions – 4 Types

3. SOLID IS PRODUCED Clear solutions when

mixed form a cloudy mixture that contains a solid called a precipitate

Evidence of Chemical Reactions – 4 Types

4. CHANGE IN COLOUR In some chemical

reactions the colour of the products is different from the colour of the reactants.

CLASSWORK

Activity 2.10 (p143) Complete and hand in BLM 2-33