Experiment to show that expired air contain water

Answer 1

Place a piece of glass in the fridge until it is cooled. Remove from the fridge, exhale onto the cool glass. Observe the droplets of water that have condensed on the cooled glass suface. You want to do this on a day when the humidity is low. This is not exactly a fool proof experiment but it is quick, easy, simple. To guard against humidity of the air condensing on the cool glass you can place a glass or plastic straw, preferably a colorless one, in the fridge and when removed from the fridge blow slowly into the tube and observe the droplets of water on the inside of the tube. With continued blowing droplets of water will drip from the end of the tube that isn't in the mouth.