Once we understand the five laws we can solve IF problems. These problems are also known as combined gas law problems. I call them IF problems because they involve an INITIAL state and a FINAL state. As an example, look at this problem:
A boy is holding a 5.00 L helium-filled balloon. The temperature of the balloon is 294 K and the pressure inside the balloon is 0.966 atm. If he accidentally lets go of the balloon and it floats up to a place high in the sky where the temperature is only 261 K and the pressure drops to 0.78 atm, what will be the new volume of the balloon?
It is worth noting that temperatures are rarely recoded in Kelvin, but we'll deal with that later.
There are two ways to solve these problems. One is purely algebraic, requiring no knowledge of gas laws at all. I will not be describing that process here, because I believe that an understanding of the gas laws is essential and that solving problems as shown here will strengthen your understanding.
The second way to solve an IF problem is to imagine each variable changing separately. Let's start setting up the problem.