## Keeping equations straight

Volume: $\Delta S = nR\ln \frac{V_{2}}{V_{1}}$
Temperature: $\Delta S = nC\ln \frac{T_{2}}{T_{1}}$

Fdonovan 3D
Posts: 101
Joined: Sat Aug 17, 2019 12:16 am

### Keeping equations straight

Does anyone have any tips on how to remember when to use each equation? I’m having a tough time trying to keep them all straight and know when to use each of them.

ELu 1J
Posts: 51
Joined: Thu Jul 25, 2019 12:16 am

### Re: Keeping equations straight

I like to take a blank piece of printer paper and write down equations based on category. Also, for internal energy = heat + work, it's helpful for me to work out when there is constant volume, delta V = 0 and thus there is no work done so internal energy = work instead of simply memorizing internal energy = work when constant v. Instead of memorizing many different equations, try to see how each equation is connected to another or how you can derive certain ones from others.

Ryan 1K
Posts: 101
Joined: Fri Aug 09, 2019 12:15 am

### Re: Keeping equations straight

A lot of the equations tie in with each other and are used in junction to solve for certain values. I have found it helps to think of the P and V when reading a problem. Visualizing the system and asking yourself if the pressure or volume is changing is a key step to deciding which equation to use since different equations apply to different P and V conditions. As for memorizing the equations, I'd suggest keeping track of what each variable stands for and how they all relate to the system, whether it's the change in internal energy or the entropy of a system.