Everyone probably already knows about the density triangle. If not, here is a quick overview.
Density
The density of a material is a measure that is independent of the size of that object. You can calculate the density with this formula:
Simple, right? The density is just the mass divided by the volume. NOT SO FAST. Suppose you have the following question on a test:
Now you are in trouble. You have a formula for density, but you don't have a formula for mass. What to do? No need to fear, there is the density triangle to save your science grade. Start with this diagram:
Here is how it works. If you want to find the mass (m), just circle the mass. The stuff left over tells you what to do with the remaining two variables. Let me illustrate:
If you need to determine the volume, circle the "V". What you have left is the m over the d. Simple.
Gas Laws
We need innovation in education. We need it now. So, I am proud to say that the faculty at Southeastern Louisiana University are here to save the day. Thomas Sommerfeld and David Norwood have proposed a solution to the infamous gas laws. The gas law (ideal gas law) is a relationship between pressure (P), volume (V), the number of moles (n), and the temperature (T). It can be expressed as the following equation:
(In physics, we usually write this as PV = NkT) But alas, we are in the same problem. How do you determine the pressure if you are given everything else? What if you need to solve for the temperature? Of course, one solution would be to memorize all the gas law equations like this:
The Gas Law Pentagram
Here is the pentagram.
To use the pentagram, just do the following:
- Choose the variable you need to determine the value for.
- Look at the pentagram. Find your variable in either the outer points of the pentagram or the inner pentagon. You want to pick either the inner or outer so that the variable you want is on the bottom.
- Look at the remaining letters. They will be in the correct position for the solution of your desired variable. Thus letter on the top will be in the numerator and letters on the bottom will be in the denominator.
Example: Suppose I need to determine the number of moles (n). I will circle the purple n on the outer part of the pentagram. The letters left over are P and V on the top and R and T on the bottom. This means that:
See. That wasn't so difficult, was it? This new method will make introductory chemistry easy once again. I can't wait to see a diagram like this show up in an introductory chemistry textbook.
