Celsius, Fahrenheit, and Kelvin are all ways to measure temperature. All three temperature scales are used in different parts of the world and in different fields of science. It’s important to remember which scale you’re using, especially if you’re doing experiments or working with temperature-sensitive materials.
Celsius is a temperature scale where water freezes at 0 degrees Celsius (written as 0°C) and boils at 100 degrees Celsius (written as 100°C). It is named after the Swedish astronomer Anders Celsius. So when you see a temperature written as “25°C,” that means it’s 25 degrees above the freezing point of water.
Fahrenheit is another temperature scale where water freezes at 32 degrees Fahrenheit (written as 32°F) and boils at 212 degrees Fahrenheit (written as 212°F). It is named after the German physicist Daniel Gabriel Fahrenheit. So when you see a temperature written as “75°F,” that means it’s 75 degrees above the freezing point of water.
Kelvin is a temperature scale that starts at absolute zero, which is the coldest possible temperature. Absolute zero is at 0 Kelvin (written as 0 K), which is equivalent to -273.15°C or -459.67°F. At this temperature, all thermal motion stops and the system is in its lowest possible energy state. The So when you see a temperature written as “300 K,” that means it’s 300 units of heat energy above absolute zero.
The Kelvin scale measures the amount of heat energy in an object. For this reason, negative Kelvin temperatures are not physically possible in most systems. According to the laws of thermodynamics, it is not possible to cool a system below absolute zero in the normal sense, because this would imply that the system has a negative amount of energy. However, in some special cases, it is possible to create systems have negative Kelvin temperatures. This occurs in certain quantum systems with a limited number of energy levels, where adding energy can cause the system to become more ordered, rather than more disordered, as would be expected at normal temperatures. While these negative Kelvin temperatures may seem counterintuitive, they are an interesting area of research in physics and can help us better understand the behavior of quantum systems.