PURPOSE: To demonstrate that the maximum density of water occurs around 4 degrees centigrade.

DESCRIPTION: A quartz flask (very small thermal expansion) holds water at 0 degrees centigrade (in an ice bath). The water fills the entire volume under the stopper and extends up into a capillary tube. When the flask is removed from the ice bath its temperature rises, as can be read on the thermometer. The water level in the capillary tube initially goes down, but reaches a minimum level at about 4 degrees and then rises as the temperature continues to increase. The photograph at the right is a close-up that permits both reading of the temperature and observation of the water volume.

This property of water is anomolous in that it is one of only a very few substances that behave in this manner. See the web site Forty-one anomalies of water for a detailed discussion of a large number of anomalous behaviors of water.

Click your mouse on the photograph at the right above to see the data taken at about three minute intervals over a 50 minute period.

SUGGESTIONS:

See Question of the Week #139 for information on using this demonstration to enhance class involvement.

REFERENCES: (PIRA 4A20.35)

EQUIPMENT: Quartz flask with water, rubber stopper, thermometer, capillary tube, container of ice.

SETUP TIME: 20 min.