The form of energy used in cooking is thermal energy, or heat. There is a variety of chemical reactions that can take place during cooking and baking. Heat speeds up the decomposition of baking soda which produces the carbon dioxide gas bubbles that cause baked goods to rise. It also denatures proteins, such as when eggs are heated.
The forms of energy are thermal, electrical, mechanical, chemical and light. The thermal energy used in cooking can come from electrical or chemical sources. An electric range uses high resistance to convert electrical energy to heat. A gas range releases the chemical energy stored in natural gas through combustion. Thermal energy can be thought of as a reactant in the case of an endothermic reaction, and can be thought of as a catalyst when it simply provides the activation energy to initiate a exothermic reaction such as lighting a fire.