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Question
A piece of ice is heated at a constant rate. The variation of temperature with heat input is shown in the graph below:

(i) What are represented by AB and CD?
(ii) What conclusion can you draw regarding the 110°c nature of ice from the above graph?
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Solution
(i) AB part of the graph represents time in t seconds taken by ice at 0°C to convert into water at 0°C.
CD part of the graph represents time in seconds taken by water at 100°C to convert into steam at 100°C.
(ii) From the graph, we conclude that ice takes less time in heating from -10°C to 0°C. But in the process of melting, it takes comparatively longer time. It shows that ice has a high specific latent heat of fusion.
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Numerical Problem.
How much heat energy is required to change 2 kg of ice at 0°C into water at 20°C? (Specific latent heat of fusion of water = 3,34,000 J/kg, Specific heat capacity of water = 4200 JKg–1K–1).
The diagram below shows a cooling curve for 200 g of water. The heat is extracted at the rate of 100 Js-1. Answer the questions that follow:

- Calculate specific heat capacity of water.
- Heat released in the region BC.
A metal ball of heat capacity 50J/°C loses 2000 J of heat. By how much will its temperature fall?
