Heat measures the movement of molecules in an object, while temperature measures the average energy or heat generated by the molecules in an object. The faster the molecules move, the more heat they produce and the higher their temperatures become.
Molecules are clusters of atoms, which are always in motion. As they bump and slide into each other, they vibrate back and forth and this motion produces heat. Many types of energy are converted into heat, including electrical, mechanical and chemical energy. Electrical energy occurs when you use a heating pad, a toaster or a light bulb. Mechanical heat, for example, is produced when a ball is bounced on the floor. The ball slows with each bounce because some of the motion of the ball's bouncing heats up its surface. Chemical heating occurs when your body uses food as fuel to warm you up.
Temperature determination depends on the size and density of the object being heated. A large object has a lower temperature than a small one, because the kinetic energy or movement within the smaller object is more concentrated and there is less room for it to disperse. Therefore, these molecules just vibrate, which causes more friction and raises the temperature of the object.