Question

A variety of observations can indicate whether or not a chemical reaction is happening when chemicals are mixed. Which of the following is most likely to indicate a chemical change when a fuel burns?

A. no gas bubbles form

B. a clear solution is formed

C. the mixture changes temperature

D. there is a coloured flame

Answer 1

Burning gas in a Bunsen burner is also a chemical change. The methane gas burns with oxygen in the air to form two new substances: carbon dioxide and water vapour. During this chemical reaction heat is also produced. When you try to light a piece of solid wax it melts, but does not burn.

The answer is A. No gas bubbles form.