Activity 3: Background Information

What is Energy?
The concept and importance of energy cannot be easily summed up in one statement. Loosely speaking, energy has to do with the motions of matter, or the potential motions of matter. Energy is often defined as the ability to do work. When work is done, energy is transferred from one object to another. Energy can take on many different forms. Kinetic and gravitational potential energy are just two forms. Other forms include: heat or thermal energy, chemical potential energy, electrical energy, electromagnetic energy, sound energy, geothermal energy, wind energy, solar energy, and nuclear energy. The standard unit of energy in science is the joule. The unit was named in honor of James Prescott Joule, an English scientist who lived from 1818 to 1889. Joule was motivated by theological beliefs and wanted to show the unity of all the forces in nature. In the 1840s he determined the mechanical equivalent of heat by measuring the change in temperature produced by the friction of a paddle wheel attached to a falling weight.

Thermodynamics

Thermodynamics is the branch of physics that deals with the nature of heat and its conversions to other forms of energy. The principle of the conservation of energy states that energy can neither be created nor destroyed. A body contains a total amount of energy as a result of the positions, motions, and chemical nature of its atoms and molecules. This is called internal or intrinsic energy. Bodies can change their internal energy by absorbing or giving off heat, by having work done on them, or by doing work. The first law of thermodynamics relates changes in internal energy to heat added to a system and the work done by a system. If a body undergoes a process of heat and work transfer, then the net heat supplied, plus the net work input, is equal to the change in internal energy.

The second law of thermodynamics is related to entropy. Entropy is a measure of disorder. The entropy of the universe increases.
What this means is that an energy transfer is not a two-way street. It is impossible to convert all the heat from a given body into mechanical work.