Final answer:
When placing an ice cube at −15° C into 0° C water, heat will flow from the water to the ice, causing the ice to warm up but not immediately melt. The ice will increase in temperature until it reaches 0° C, and only then will it start to melt, maintaining the temperature during the phase change.
Step-by-step explanation:
If you were to place an ice cube with a temperature of −15° C into a bowl of water at 0° C, the following would immediately happen:
- Heat would flow from the water into the ice cube, causing it to increase in temperature (c). This is due to the second law of thermodynamics, where heat flows from a warmer object to a colder one until thermal equilibrium is reached.
- The heat from the water to the ice cube would not cause more water to freeze (b), as the ice cube is already below freezing and must reach 0° C before it can begin to melt.
- The water temperature will not decrease as the ice is absorbing the heat (d), keeping the water at 0° C.
- Some of the ice cube may begin to melt as it reaches 0° C, but initially, the temperature of the ice cube will increase without melting (a and c).
As the ice cube absorbs heat, it will undergo a two-step process. First, its temperature will rise to the melting point (0° C) without undergoing a phase change, and only then will it start to melt while remaining at the same temperature during the phase change. The melting occurs because the heat absorbed is used for the phase change from solid to liquid, known as the heat of fusion.
Similar principles apply when considering ice in an insulated container with 0° C water. The ice melts gradually, and the system maintains a temperature of 0° C as long as there is ice present because of the thermal equilibrium between the ice and water.