People detect the transfer of heat, naturally, by noting changes in temperature. Yet heat and temperature measure different things. Heat measures energy. Temperature instead describes the average energy throughout the particles of a substance, which all vibrate with kinetic energy. A hot skillet therefore feels hotter than a heated bath because of its higher temperature, but it takes a higher energy transfer to heat the tub of water. Calculate energy transfer using temperature change and the substance's capacity for heat.
Determine the substance's temperature rise. If a quantity of water, for instance, rises from 20 degrees Celsius to 41 degrees: 41 - 20 = 21 degrees.
Multiply the result by the substance's mass. If 200kg of water, for instance, raises 21 degrees in temperature: 21 x 200 = 4,200.
Multiply this product by the substance's specific heat capacity. With this example, which uses water, whose specific heat capacity equals 4.186 joules per gram: 4,200 x 4.186 = 17,581.2, or approximately 17,500 joules. This is the amount of energy that is transfered during the heating process.