Abaker prepares two pans of cake batter. when one pan is put in an oven, the butter bakes into a cake. the other pan is left on a countertop and the batter remains unchanged. both pans contained the same chemicals. why do the chemical reactions involved in baking only occur in one of these pan of cake batter?

Because, the cake that was put into the oven was baked therefore changing its form and cooking the ingredients inside. The cake that was left out on the counter top had no changing factors because there was nothing being done to the cake, therefore remaining in its un-baked state.

nuclear fission produces elements that are heavier than helium.

the elements that are used in nuclear fission and their products are much heavier than helium.