Question

A glass tumbler containing hot water is kept in the freezer compartment of a refrigerator (temperature < 0°C). If you could measure the temperature of the content of the tumbler, which of the following graphs (Fig.) would correctly represent the change in its temperature as a function of time.

• A.

  

• B.

  

• C.

  

• D.

  

Answer 1

The correct option is A

Explanation for the correct answer:-

Option (A)

• The temperature of the water that is kept in the tumbler will first fall down initially when kept in the refrigerator till it reaches $0°\mathrm{C}$.
• After reaching this point, the temperature remains constant for some time until all the water gets turned into ice.
• After turning into ice the temperature will start decreasing again and get below $0°\mathrm{C}$
• Hence it is the correct option.

Explanation for the incorrect answer:-

Option (B)

• The temperature does not decrease at a steady rate as shown in the graph.
• It first decreases to $0°\mathrm{C}$ , stay constant for sometime and then gets converted to ice.
• Then it decreases below $0°\mathrm{C}$.
• Hence it is the incorrect option.

Option (C)

• The temperature does not stay constant at $0°\mathrm{C}$ forever as shown in the graph
• After getting converted into ice it decreases below $0°\mathrm{C}$.
• Hence it is the incorrect option.

Option (D)

• After reaching $0°\mathrm{C}$ and getting converted into ice, the temperature does not rise up as shown in the graph.
• This is not possible because the temperature inside the refrigerator is below $0°\mathrm{C}$.
• Hence the temperature decreases.
• Hence it is the incorrect option

Therefore, option (A) is the correct answer