Please explain me Hope's Experiment in brief and in clear words

Dear student,

In 180, T.C. Hope devised a simple arrangement as Hope's Apparatus for demonstrating The anomalous expansion of water.
The apparatus consist of a tall metallic cylinder provided with two side openings, one near the top and other near the bottom, fitted with thermometers T1 abd T2.

The central part of cylinder is surrounded with a cylindrical trough containing a freezing mixture of ice and salt.
The cylinder is fitted with pure water at room temperature.

Initially both the thermometers T1 and T2 show same temperature.
First the thermometer recorded by lower thermometer T2 starts decreasing and finally becomes steady at 4⁰c, while the temperature recorded in upper thermometer T1 remains unchanged during this time.
Then the temperature recorded by the lower thermometer T2 remains constant at 4⁰c. and the thermometer T1 near the top records continuous fall in temperature up to 0⁰c.and then it becomes steady.
thus final temperature T1=o⁰c

explanation:initially the water in the cylinder is at room temperature. as the freezing mixture cools the water in the central position of the cylinder, the water the density of water increases and sinks to bottom thus decreasing  the temperature of lower thermometer T2 to fall rapidly. The thermometer T1 does not show change.This continues till the temperature of entire water below the central portion reaches 4⁰c.
On further cooling 4 ⁰c, , due to anomalous expansion the water in central portion expands. as a results, the reading of upper thermometer T1 falls rapidly to 0⁰c. and ice begins to form near the top. The water at the bottom still remain at 4⁰c.
Conclusion: the expansion of water when cooled from 4 ⁰c to 0⁰c is known as anomalous expansion of water.



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