Demonstrations
The Volume-Temperature Relationship In Gases
In the first several frames of this demonstration liquid nitrogen is being transferred from one Dewar flask to another. The liquid nitrogen has a boiling point of -173 °C and in order to maintain it in the liquid state for short periods of time these highly insulated containers must be used for storage. The red balloon is filled with oxygen gas and is then slowly immersed in the liquid nitrogen. As the temperature of the balloon and its contents are lowered, the volume of the gas decrease. Because the boiling point of oxygen is slightly higher than that of nitrogen, the oxygen in the balloon eventually condenses to the liquid state and the balloon then collapses to the volume occupied by the liquid oxygen (about 1 milliliter). The last frames show the balloon beginning to assume its original shape as the temperature and volume of the oxygen increase.
Collection Of A Gas Over Water
A small sample of zinc has been placed in the outer test tube. A smaller inner test tube contains hydrochloric acid. When the tube is inverted, the hydrochloric acid is mixed with the zinc and reacts with it to produce hydrogen gas. The gas occupies a volume greater than that of the test tube and consequently moves through the rubber tube into the graduated cylinder filled with water. Because the hydrogen is not appreciably soluble in water and is less dense than the water, it displaces the water and moves to the top of the graduated cylinder.