Physical and chemical changes are associated with energy changes. This leads to a change in the energy of the system. It is seen in the form of heat transfer. As example, plants process light energy in the form of chemical bonds inside large macromolecules like carbohydrates, proteins, and fat. And this chemical energy reaches other organisms via the food chain. We can utilize the energy through metabolic activity which releases the energy slowly through chemical reactions. How can we measure this energy change? Calorimetry provides one answer to this problem. An ordinary calorimeter is an insulated flask which can prevent heat from flowing into or out of the system. Any heat generated or absorbed is then going to change the temperature of the contents. This is how we measure the heat change.