The Laws of Thermodynamics: What They Are and How They Work
The laws of thermodynamics are the rules that define how energy and matter move around and change form within our universe. When it comes to the laws of thermodynamics, there are four major ones to consider—namely, the first, second, third, and zeroth laws of thermodynamics. In this article, we’ll look at what each of these laws say and why they’re relevant to human beings on a day-to-day basis, as well as any other organisms out there in the natural world. Let’s begin with the first law of thermodynamics...
Law #1 - Energy can be neither created nor destroyed, only converted
If you understand nothing else about thermodynamics, it’s important to understand that first law. The conservation of energy is one of those rules that seem so basic we forget just how astonishing it is. Energy can neither be created nor destroyed! When you burn fuel in your car, or any other machine, what’s really happening is that energy is being converted from one form to another. The heat produced by burning fuel can be used to generate electricity, run a heater or make ice cubes in your refrigerator. It sounds like magic—but it isn’t (though sometimes it seems like it).
Law #2 - Matter can neither be created nor destroyed, only changed
This law means that matter is neither created nor destroyed in chemical reactions. Matter can change form, but not be produced or destroyed. One example of a violation of Law #2 is nuclear reactions; see Law #3 below for more information. Chemical reactions can be reversible or irreversible, however both types are still governed by Law #2. For example, rusting iron follows an irreversible process because it cannot be undone once started. However, dissolving salt in water can be reversed with changes in temperature or by adding more salt; if you did add more salt to your sugar-water (like you might make up for a missed teaspoon), then your sugar would dissolve back into plain water because it will equalize with whatever concentration is available.
Law #3 - When energy is transferred, it will always pass from a system at a higher temperature to another system at a lower temperature
Temperature is a measure of how hot or cold something is. This means that when energy changes form, it will always pass from a system at a higher temperature to another system at a lower temperature. While these two systems may not necessarily be in direct contact with each other, as long as there is an intermediate medium for exchange (e.g., air or water), heat will always flow from hotter to colder environments until equilibrium between temperatures is achieved. The result? Hotter regions eventually cool down and colder ones warm up. So what does that mean for us in terms of daily life?
Law #4 - Entropy must increase in every process
The natural flow of energy is from a state of higher concentration to a state of lower concentration. When we burn gasoline in our cars, for example, it converts chemical energy into thermal energy (exothermic). When that thermal energy is converted into mechanical force to turn our wheels, it becomes kinetic energy. However, these two forms are not equal. Kinetic energy is half as concentrated as what was in gasoline. The second law says that every process will result in more entropy, i.e., disorder or randomness, than what existed before it occurred.