Introduction: Air pressure is used to crush a soda can which shows the effect of the Gas Laws.
- Fill a shallow dish like a pie pan, with water.
- Take an empty soda can and fill it with water. Then pour the water from the can into a measuring cup to determine the volume it can hold.
- Now add a small amount of water into the can and then heat the can on a stove until steam is produced. Wear safety goggles and an apron.
- Using tongs quickly invert the soda can and place it into the shallow dish of water so the opening is under water.
- The can will collapse under air pressure.
- Remove the can and let it cool.
- Fill the can with water, but don't allow the sides to pop out.
- Dump the water from the can into a measuring cup and determine the volume.
- Compare this volume with that held by the original can.
Discussion
Discussion
Air has mass and takes up space (volume). Because it is a fluid it will have pressure that is dependent upon the weather and your height above or below sea level. Normal pressure is considered to be 760 millimeters of mercury (Hg). Heating air causes the particles to move further apart thus reducing the pressure in an open container. The result is a partial vacuum. We used a little water in this demonstration because the volume change from the gaseous state to the liquid state is reduced by a factor between 600 and 1,000 (according to Flinn Scientific 1996 catalog page3). The can is crushed by the higher pressure outside until an equilibrium is reached. The can itself is a factor in how far the crushing can take place.
You can demonstrate space between particles by getting a bunch of people to stand in a line all looking at the back of the person in front of them. Then start walking slowly starting on the left foot with someone calling out the pace. The person calling should speed up the pace and see what happens. People will spread out as they begin to run resulting in empty space between them just like a vacuum.
