After reading the Mayor of Casterbridge for three hours straight this afternoon, I decided to take a break and wake up my brain with a little physics adventure. Since I had been drinking a can of juice while enjoying the amazingly exciting and action-packed life of Mr. Henchard, I went to try out an idea (that I must have read or heard somewhere) that will help me remember forever the significance of the idea gas law (which will probably come in handy for the AP exam). So thus determined, I turned on one of the plates in the kitchen, poured in a little bit of water into the can and set on it on high until i could see steam coming out of its opening. Ready with my bowl of cool water and a oven mitt, I grabbed the juice can and turned it over in the cold water. Immediately, before I could prepare myself, the can was crushed by the atmospheric pressure. It was quite sudden and effective and I actually jumped (and sloshed quite a bit of water over the side…) This is probably the most elementary of physics problems ever, but it still took by surprise! (I can’t believe I hadn’t tried it sooner).
Anyways, the whole point of the exercise was a to find a way for me to set down to memory the relationships between pressure, temperature, and volume and here it is: PV = nRT
As the temperature inside the container heated up and the water begins to boil, gaseous water vapor begins to take up some of the volume of the can and forces out dry air. (The vapor actually occupies approximately 1000 times more space than it did as a liquid). When the the can is turned over into the cool water the water vapor condenses back to liquid water very quickly creating a partial vacuum in the can. Since the hole in the can is submerged in water, air is not able to rush in and fill that volume. With very little air inside the can the air pressure inside the can is much less than the atmospheric pressure outside of it. The can is crushed by the net inward forces exerted by the pressure difference.
Furthermore, since the air pressure pushing down on the water outside of the can was much greater than the air pressure pushing down on the water through the drinking hole of the can, water was drawn up into the can (which explains why it sank…).
Comments on: "CAN CRUSH" (2)
My coke can didn’t crush! Should my cool water come from the refrigerator are sink?
Whether the water is refrigerated or not should no matter so much in this experiment as long as there is a noticeable difference in temperatures of the cool water and the boiling water in the can. Just make sure to be speedy about transferring the can from the hot plate to the water since you don’t want to let all the hot gas inside escape.