Explain whether the following changes are physical or chemical or both-
1. Glowing of an electric bulb.
2. Combustion of coal, wood, oil.
3. Digestion of food
4. Curdling of milk
5. Conversion of crude oil into gasoline.
6. Ripening of food
7. Growth of plants and decay of vegetation
8. Hardening of mortar
9. Evolution of gas that occurs when baking powder is moistened.
Give reasons for your answers.