The graph shows the changes in the phase of ice when it is heated.

which of the following temperatures describes the value of b?

a) 0 °c, because it is the melting point of ice.

b) 100 °c, because it is the boiling point of water.

c) greater than 0 °c, because a represents the temperature at which ice melts

d) greater than 100 °c, because a represents the temperature at which water evaporates.

Option (A) is the correct answer.

Explanation:

A temperature at which both solid and liquid state of water are present in equilibrium is known as melting point and the temperature remains constant during this transition of phase.

As it is shown in the graph that temperature at point A is zero degree celsius that is, the temperature at which water freezes completely. And, point B shows that solid and liquid phase are in  equilibrium. This means that the temperature at point B is also zero degree celsius.

Hence, we can conclude that temperature at point B is , because it is the melting point of ice.  

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