This is a blog of the 4th grade class in la Farigola de Vallcarca School in Barcelona. This year we are doing “Aula de Ciències” in English.
In this blog we want to show you the experiments we do in our Science Lab. Science is fun!

dimarts, 24 de maig de 2011

Atmospheric pressure

atmospheric pressure on PhotoPeach

MATERIALS: A can Cooking tongs A camping stove A bowl with cold water INSTRUCTIONS: - Put some water in the can (a tablespoon). - Place the can on the stove. - Heat the can to boil water. You can see the water vapor rising from the can. Wait one minute. - Hold the can with the tongs. - Take the can, turn it upside down very quicky and dip it into the water in the bowl, so the hole is covered by water. - The can crushes. - We did the same, but we placed it on the water with the open on the top: it happened nothing. WHY?: By boiling the water, the water changes states from a liquid to a gas (vapor). The water vapor expands and pushes the air out of the can into the atmosphere. When we turn the can upside down and place in the water, the water vapor cools, condenses, contracts and the pressure in the can decreases. Then the pressure from the outside of the can (atmospheric pressure) is higher, pushes the can and crushes it . When we do the experiment with the opening on the top, the air from the outside goes in the can and the pressure in and out the can is balanced.