Question

How to study the anomalous behaviour of water by using Hope's Apparatus?

Answer 1

Hint: Anomalous expansion of water occurs when water is cooled from $4{}^\circ C$ to $0{}^\circ C$.

Step by step answer:
The Hope’s apparatus requires a high metallic lattice cylinder with two side openings, one near the top and the other near the bottom of the cylinder, both filled with thermometers. In the middle portion of the cylinder, it is surrounded with a cylindrical trough which contains a freezing mixture of salt and ice. The cylinder is then filled with pure water at room temperature.
The observations of this experiment signify that in the beginning, both thermometers show the same temperature, then the lower thermometer records low temperature and starts decreasing. It finally becomes steady at $4{}^\circ C$ while the temperature recorded in the upper thermometer remains unchanged during this time. After sometime, the temperature recorded by the lower thermometer remains constant at $4{}^\circ C$ and in the upper thermometer, the temperature recorded continuously falls till it is $0{}^\circ C$ and then it becomes steady.

Additional Information: Thomas Charles Hope was the professor of chemistry at Edinburgh University from 1795 to 1843. In 1805, he had published a paper on “Experiments and observations upon the contraction of water the heat at low temperatures' '. In that experiment, he had shown how water has its maximum density at about $4{}^\circ C$, which was a fact known only to those fishes which used to congregate at the bottom of ponds in freezing weather.

Note: Some simple steps to study the anomalous behaviour of water by using Hope’s apparatus are:
Along with Hope’s device, cool a beaker filled with water an hour before conducting the experiment.
Make a cooling mixture using crushed ice and salt.
Isolate the device and put two thermometers into the two holes of the apparatus respectively.
The inner cylinder is filled with pre-cooled water while the outer cylinder is filled with the cooling mixture.
The temperatures are observed on the thermometers and anomalous behaviour of water is noted.