
Mass
WHAT: This is the amount of a substance. This is how much stuff is in something. Sometimes mass is confused with weight. Weight is a measure of mass based on how much gravity there is in the system. Mass is usually measured in grams.


Energy
WHAT: We know it's kind of in the area of physics, but "E" stands for energy. Remember the famous formula E=mc^{2}? That "E" is energy and it is equal to a mass multiplied by the speed of light and then multiplied by the speed of light again.


Speed of Light
WHAT: Yes, "c" is a constantis a constant and it represents the speed of light in a vacuum. It is used in the equation E=mc^{2}.


Total Pressure
WHAT: We say that this is the symbol of total pressure. That is all of the pressures added together. It is the pressure value from the equation PV=nRT. There are separate values and symbols for the partial pressures in a system.


Volume
WHAT: The symbol for volume, usually measured in liters. It's how much space your mass fills up. You'll see V in the famous equation PV=nRT.


Number of Moles
WHAT: A mole measures the number of molecules, or atoms. So, when you see the value "n", you know how many moles are in a system. A mole is 6.02x10^{23} molecules or atoms. You could also say that you have 2 mol of a substance (yes, the "e" disappears when you write it as a unit). We'll mention PV=nRT again.


Gas Constant
WHAT: For PV=nRT. You can't escape the ideal gas law in chemistry That "R" is a constant. It's an important one to remember because you will find it in other scientific equations. "R" is the molar gas constant or the ideal gas constant.


Temperature
WHAT: Last time. PV=nRT. That's the last one (at least on this page). That "T" stands for the temperature of the system. You will use temperature values in Kelvin.


Relative Density
WHAT: Density is how much things are packed together. It tells you how much stuff (mass) is found in a certain amount of space or volume (D=m/V). Imagine a solid cube that is one centimeter tall, one centimeter wide, and one centimeter long. If that cube is filled with Styrofoam, it is light. If it is filled with lead (Pb), it is heavy. The lead is heavier because it has a higher density than Styrofoam.


Molarity
WHAT: This is the symbol for molarity. When chemists talk about the concentration of substances dissolved in solution, they say it has a specific molarity. It is the number of moles (mol) that are dissolved in a specific volume (liters).
