What is First law of thermodynamics?
The '''first law of [[thermodynamics]]''' is that '''[[energy]] can neither be created nor destroyed; it can change only from one form to another'''. The law forms the basis of the principle of [[conservation of energy]]. This means that anything that uses energy is changing the energy from one kind of energy to another. For example, [[Exercise|exercising]] changes energy from [[food]] into [[Kinetic energy|kinetic]] (motion) energy. Another example: In the [[Sun]] (or any star), [[nuclear fusion]] changes '''mass '''into heat and light ([[electromagnetic radiation]]), which travels to [[Earth]] and is used by [[Plant|plants]] to create food ([[chemical energy]]) by [[photosynthesis]], which can be eaten by [[Animal|animals]] allowing them to move (kinetic energy). Energy only ever changes its form; it is neither created nor destroyed. This is why [[perpetual motion]] machines do not exist and could '''never''' exist; it would break a fundamental [[Laws of physics|law of physics]]. People can use the changes to do work that is useful.<ref>[https://web.chemistry.ohio-state.edu/~woodward/ch121/ch5_law.htm 1st Law of Thermodynamics]{{Dead link|date=January 2021 |bot=InternetArchiveBot |fix-attempted=yes }} Ohio State University. Accessed July 2011</ref> Examples of forms of energy in [[classical mechanics]] include [[heat]], [[light]], [[Kinetic energy|kinetic]] (movement) or [[Potential energy|potential]] energy. However, in modern physics it is considered that there are only two types of energy - [[mass]] and kinetic energy, although this may not be helpful to those not familiar with more complex physics. The law means that the total energy of the universe (or any [[Closed system]]) is a constant. However, energy can be transferred from one part of the universe to another. The most common wording of the first law of thermodynamics used by scientists is: {{cquote|The increase in the internal energy of a thermodynamic system is equal to the amount of [[heat|heat energy]] added to the system minus the [[Work (