Explaining Chemical Reactions Formal models

Activity 1 Burning a candle. Place a candle on a heatproof mat. Light the Candle and watch carefully what happens.

1 When the candle burns, what happens to the wax around the wick?

2 Does the candle get smaller as it burns? 3 What is burning?

4 Where do you think the wax is going? 5 Could you collect it again?

6 Is it the same process as water evaporating? 7 If not, how is it different?

8 Would the candle burn if there was no air around it? 9 Is air used up when a candle burns? Candle under a beaker link.

10 Try to explain what happens when a candle burns, using the idea that there are oxygen particles in the air and wax particles in the candle.

Activity 2: Copper and Sulphur Describe what they look like and note there appearance.

Describe what happens when the mixture is heated. Describe what the product after heating looks like. The product is called copper sulphide.

Activity 2: Copper and Sulphur 1 Do you think it would be easy to get the copper and sulphur back from the copper sulphide? 2 What do you think has happened to the particles (atoms) of copper and the particles (atoms) of sulphur?

Activity 2: Copper and Sulphur 3 Is this the same sort of thing that happened when sulphur alone is melted in a test tube and allowed to cool again? Explain your answer.

Activity 3: Iron and Sulphur (demonstration) 1 When the burner is taken away. What did you see? 2.Does the iron sulphide look like the iron and sulphur? 3. Explain what has happened in terms of atoms of iron and atoms of sulphur.

Activity 4: Thinking Back Do you think today’s observations can be explained using the the models from heating and dissolving? As a group can you come up with a model for how substances melt, dissolve and react with other substances?

Use coloured circles to show what the wax and oxygen particles look like before they react and draw pictures of what they look like after the reaction.