1. What element is always needed in combustion?

2. What is left when all the wood gas of a wood has been burned?

3. What is left when wood is burned completely?

4. What are the most common materials used in candles?

5. What two substances are produced when a candle burns?

6. What element produces water when it reacts with oxygen?

7. What does ash consist of?

8. Why can carbon dioxide be used to extinguish flames?

9. What happens to the substances that seem to disappear during combustion reactions?

10. What are the three types of combustion?