In which of the following does a chemical change take place ? a. mixing flour ,salt ,and sugar b. baking a cake c. adding ice to water

Baking a cake would be a chemical change because the baking powder/soda undergoes through a reaction, you can tell because it generates bubbles/bumps when you bake it. 
A chemical change is also irreversible so when you bake the cake, you cannot separate the ingredients.
So your answer would be B. Baking a cake
Hope this helps !