What are the four laws of thermodynamics? I didn’t know there were four laws until researching this. Thermodynamics is the study of the relationship between heat, temperature, and energy.
The 0th law of thermodynamics states that if two systems are in thermodynamic equilibrium with a third system, the first two systems are in equilibrium with each other. Another way to say this is that all of the systems have lost or gained enough thermal energy for them to be in equilibrium with each other. (It was discovered after the other three laws, but it was thought to be more basic, so it was called the 0th law.)
An example of this is if you put a glass of hot water and a glass of chilled water on a table in a room. After a while the hot water will have lost energy to be in equilibrium with the air in the room and the chilled water will have gained enough energy to be in equilibrium with the air in the room. All three systems are in equilibrium with each other.
The 1st law of thermodynamics states that energy can be converted from one form to another, but it cannot be created or destroyed. The total energy of an isolated system is constant.
An example of this is a bath. When you heat the water for a bath you are applying energy to the water molecules that comes from electricity. The energy in the electricity has probably been made by burning coal. The energy in the coal has come from the plants that were fossilized. The energy in those plants has come from photosynthesizing the energy from the sun. The energy in the sun has come from the nuclear fusion of hydrogen atoms. And so on. Then, at the other end, when you are in the bath, the heat energy from the water is transferred to your cells and the air. The energy is never destroyed, just changed.
The 2nd law of thermodynamics states that the state of entropy of an isolated system will always increase over time. Entropy is the measure of the disorder in a system. An easy way of thinking about it is that there are far more ways something can be disordered than there are that it can be ordered. A jigsaw puzzle, for example. There is only one way it can be done. If you put all the pieces in the box and shake it, the chance that it will come out completed is far lower than the chance it will come out messed up. This is the same with everything in nature. Entropy will always increase.
An example of the second law is an ice cube on a table. When water molecules form ice, they have an ordered, rigid structure. This is hard to keep. As the water absorbs the energy in the room, the molecules start to move and spread out. The ice becomes water. This is entropy. The second law says that entropy in the universe only increases, which means that at the end of the universe, all of the heat energy in the universe will be distributed evenly and nothing will be able to happen. This is also known as heat death.
The 3rd law of thermodynamics states that a system’s entropy approaches zero as its temperature approaches absolute zero. Absolute zero is the point at which there is no heat, and that means there is no way that entropy can happen. It is basically the base of the system. However, it is impossible to reach absolute zero, because the amount of energy needed to get something that cold increases exponentially until it reaches infinity. Also, at absolute zero, there is no energy in the system, so no motion. This is not possible because atoms will always vibrate on the quantum level. So, the 3rd law of thermodynamics is correct, but it is not possible to ever reach it.
The ideas behind these three laws began in 1650. In 1798, Benjamin Thompson began to study heat as a form of energy. The first principle of thermodynamics was thought up in 1824 by Said Carnot. The laws came into their own during the Industrial Revolution because inventors and scientists wanted to make far more efficient steam engines.
The four laws of thermodynamics govern our universe. Nothing can exist that breaks one of these rules. For example, and despite people’s claims, a perpetual motion machine could not exist because it would break the first law of thermodynamics.
So, the four laws of thermodynamics explain the relationship between heat, energy, and temperature in an isolated system. And this is what I learned today.
Sources
https://byjus.com/jee/zeroth-law-of-thermodynamics/
https://www.thoughtco.com/zeroth-law-of-thermodynamics-4177952
https://www.grc.nasa.gov/www/k-12/airplane/thermo2.html
https://www.wired.co.uk/article/how-will-universe-end
http://www.csun.edu/~psk17793/G%20Chemistry/entropy.htm
https://www.thoughtco.com/definition-of-entropy-604458
https://en.wikipedia.org/wiki/Laws_of_thermodynamics
https://www.livescience.com/50942-third-law-thermodynamics.html