Q1. i. In what two ways combustion can be useful to us? Explain by giving examples. ii. Explain why decomposition of sugar on heating is an irreversible change.

6. using 3 – 4 sentences explain (in your own words) why water expands when it freezes? 7. using your knowledge of colligative properties explain whether sodium chloride or calcium chloride would be a more effective substance to melt the ice on a slick sidewalk. use 3 – 4 sentences in your explanation.