Various forms of energy can be grouped as potential energy. Each of these forms is associated with a particular kind of force acting in conjunction with some physical property of matter (such as mass, charge, elasticity, temperature etc). For example, gravitational potential energy is associated with the gravitational force acting on object's mass; elastic potential energy with the elastic force (ultimately electromagnetic force) acting on the elasticity of a deformed object; electrical potential energy with the coulombic force; strong nuclear force or weak nuclear force acting on the electric charge on the object; chemical potential energy, with the chemical potential of a particular atomic or molecular configuration acting on the atomic/molecular structure of the chemical substance that constitutes the object; thermal potential energy with the electromagnetic force in conjunction with the temperature of the object. For an example of gravitational potential energy, consider a book placed on top of a table. To raise the book from the floor to the table, work must be done, and energy supplied. (If the book is lifted by a person then this is provided by the chemical energy obtained from that person's food and then stored in the chemicals of the body.) Assuming perfect efficiency (no energy losses), the energy supplied to lift the book is exactly the same as the increase in the book's gravitational potential energy. The book's potential energy can be released by knocking it off the table. As the book falls, its potential energy is converted to kinetic energy. When the book hits the floor this kinetic energy is converted into heat and sound by the impact.