Question

Ice at temperature –10°C is converted to steam at 100°C, the curve plotted between temperature (T) and time (t) when it is being heated by constant power source is

• A.

  

• B.

  

• C.

  

• D.

  

Answer 1

The Correct Option is B

The heating process involves several stages:

Heating Ice from -10°C to 0°C: The temperature increases until it reaches 0°C.

Melting Ice at 0°C: The temperature remains constant while the ice melts into water, represented as a plateau on the graph.

Heating Water from 0°C to 100°C: The temperature of the water increases until it reaches 100°C.

Boiling Water at 100°C: The temperature remains constant as the water turns into steam, represented as another plateau on the graph.

Heating Steam from 100°C Onward: The temperature of the steam increases.

The correct graph will show:

• An initial increase in temperature from -10°C to 0°C.
• A plateau at 0°C during the melting phase.
• An increase in temperature from 0°C to 100°C.
• A plateau at 100°C during the boiling phase.
• A continued increase in temperature as steam is heated.

Answer 2

To understand the curve plotted between temperature (T) and time (t) for the process where ice at temperature –10°C is converted to steam at 100°C using a constant power source, we need to consider the phases and latent heats involved in the transformation of ice to steam. The complete process involves several stages:

1. Heating ice from -10°C to 0°C: Here, the temperature of the ice rises linearly as it absorbs heat.
2. Melting of ice at 0°C: The temperature remains constant at 0°C as the ice absorbs latent heat of fusion to become water. This stage will appear as a horizontal flat segment on the temperature-time graph.
3. Heating water from 0°C to 100°C: The temperature of the water increases linearly with time as it absorbs heat.
4. Boiling of water at 100°C: The temperature again remains constant at 100°C during this phase as water absorbs latent heat of vaporization to become steam. This also appears as a horizontal flat segment on the graph.
5. Heating of steam above 100°C: If this step occurs, steam's temperature would rise linearly as heat is absorbed further. In the context of this question, since the end temperature is stated as 100°C, it is assumed there's no further heating beyond boiling.

The correct graph representation shows these distinct phases: an initial linear increase, a flat segment at 0°C, another linear increase, and another flat segment at 100°C. Thus, the correct answer is the second figure (Fig 2), which demonstrates these characteristics.

This figure accurately represents the described sequence of heating and phase change processes visible on a temperature versus time graph for a substance undergoing heating and phase transformations.