Question

Anomalous behavior of water can be demonstrated with the help of Hope's apparatus. Arrange the following steps of changes taking place in Hopes apparatus in the proper sequence.
(A) The temperature detected by the lower thermometer reaches to $0^\circ C$ and remains constant at $4^\circ C$
(B) Water freezes into ice at $0^\circ C$, and as the density of ice is less than that of water, the layer of ice is formed at the top surface
(C) The initial temperature of water is kept constant at $10^\circ C$. The temperature of water begins to fall because of the freezing mixture at the centre and it contracts.
(D) When temperature of water decreases from $4^\circ C$ to lower temperature, water expands instead of contracting and its density decreases. So, water goes up from the centre portion.
(E) The cold water goes to the bottom, as the density increases and the temperature shown by the lower thermometer falls.
(F) The temperature of water at the top of the cylindrical jar begins to fall till $0^\circ C$ which is shown by the upper thermometer.
(G) Ice prevents the loss of heat from water below it into the surroundings because it is a bad conductor of heat.
A. CDBFAGD
B. CEADFBG
C. CEAFDGB
D. CBEGDAF

Answer 1

Hint: There is an abnormal property of water known as anomalous expansion of water in which it expands instead of contracting when the temperature goes from $4^\circ C$ to $0^\circ C$ , and it becomes less dense. This anomalous expansion of water can be studied through Hope’s experiment which consists of a unique apparatus known as the Hope’s apparatus.

Complete step by step answer:
Let us first discuss the anomalous expansion of water.
There is an abnormal property of water known as anomalous expansion of water in which it expands instead of contracting when the temperature goes from $4^\circ C$ to $0^\circ C$ , and it becomes less dense. The maximum density is observed at $4^\circ C$ and decreases below that temperature. The density decreases as it freezes because molecules of water form open crystal structures normally when in solid form.

This anomalous expansion of water can be studied through Hope’s experiment which consists of a unique apparatus known as the Hope’s apparatus.
In Hopes apparatus there is a long cylindrical jar with two openings on the side, one near the bottom and the other near the top and they are used to fit thermometers in each of these openings. On its central portion, a metallic cylindrical air-tight trough with an outlet is also fitted onto the jar. The cylindrical jar is now filled with water. The central portion of the jar consists of the cylindrical trough which is filled with a freezing mixture of ice and common salt. After a period of time the denser water collects at the bottom at a temperature of $4^\circ C$ which shows the anomalous behavior of water.
So, the steps involved in this process in order will be:
(C) The initial temperature of water is kept constant at $10^\circ C$ . The temperature of water begins to fall because of the freezing mixture at the centre and it contracts.
(E) The cold water goes to the bottom, as the density increases and the temperature shown by the lower thermometer falls.
(A) The temperature detected by the lower thermometer reaches $0^\circ C$ and remains constant at $4^\circ C$.
(D) When temperature of water decreases from $4^\circ C$ to lower temperature, water expands instead of contracting and its density decreases. So, water goes up from the centre portion.
(F) The temperature of water at the top of the cylindrical jar begins to fall till $0^\circ C$ which is shown by the upper thermometer.
(B) Water freezes into ice at $0^\circ C$ , and as the density of ice is less than that of water, the layer of ice is formed at the top surface.
(G) Ice prevents the loss of heat from water below it into the surroundings because it is a bad conductor of heat.

Hence, option (B) is correct.

Note: The main reason behind the anomalous behavior of water is that the water molecules are associated by hydrogen bonding as water has greater polarity. In a water molecule there is one oxygen atom combined with two hydrogen atoms. The water molecules are held together in a liquid state at normal room temperature because of the intermolecular attraction of the water molecules.