Energy is defined as the capacity to perform work or to produce heat. The Systegrave;me International d'Unités (S.I.) unit for energy is the joule (J). Lifting a medium-sized potato a distance of one meter against gravity would require approximately one joule of energy. Energy is often expressed as the calorie (cal), which is the amount of heat needed to raise the temperature of one gram of water by one degree Celsius. One calorie is equal to 4.184 joules. The Calorie (Cal), which is how the energy in food is expressed, is 1,000 calories. Energy is not only involved in chemical reactions and technology, but also in our basic bodily functions. It is because of the energy of the reactions inside of our body that we maintain a constant body temperature, our heart and lungs can function, and our muscles can move. Energy can take many forms...