Have you ever wondered why squeezing the trigger of a water pistol shoots out a stream of water? Why is it that pumping air into tires makes them rounder? Why do popcorn kernels pop when you heat them? The answers to these questions involve the concept of pressure, and the goal of the demonstration outlined on this site is to show students three ways of adjusting the pressure within a system (adding or removing particles, changing the size of the container, and adding or removing energy) and the effects of doing so. An initial activity is explained below that introduces all of these concepts by having the students walk around as air particles interacting with other particles (students and furniture) within the system (the classroom). For more information on this activity, click on the classroom photo below. A series of short youtube videos incite interest in the students by showing them the water pistols and tire pumps in action. These videos can be found in the powerpoint slides, which can be downloaded by clicking the picture of the projector. Then a series of demonstrations is used to show to students the surprising outcomes that can be observed by changing the pressure of a system. First, we show how pressure holds water in a pierced water bottle. Then, we show how atmospheric pressure can be used to help a single sheet of newspaper apply enough resistive force to snap a wooden stick. Next, we show how removing heat from a system can cause still water to boil again by adjusting the pressure of the system. Finally, we end with a worksheet to make sure that the demonstrated concepts have been absorbed by the students. Each of these are explained in full in their corresponding pages below.