Condenser (apparatus)
A condenser is a device used in the laboratory to cool hot gases into liquids. It is usually a long, circular glass tube. Inside the tube there is another, smaller tube. The hot gas goes through the smaller, inside tube, while in the outside one cold water goes around. Water can be put in from the tap, and goes from the bottom to exit at the top. This makes sure the tube is always full of water, so that cooling is quick.