Question

A 50g cube of ice and 500g of boiling water are mixed in an open container. Which of the following is most likely to occur?
A. The ice cube vaporizes before it strikes the bottom of the container
B. The water boils more vigorously because the hot water draws cold from the ice cube
C. The water in the container stops boiling during the phase change of the ice to water
D. The more dense ice cube sinks in the less dense hot water
E. Steam bubbles form on the ice cube

Answer 1

Hint: The phase change of ice to water requires less heat energy than the phase change from water to steam. A process which requires less energy to occur will happen faster in nature. This is almost obvious since the most important prerequisite of undergoing a process or a reaction is to get the energy to start it. If the energy requirement is low, it will happen faster.

Complete Step-by-Step solution:
When the ice cube is mixed in the boiling water, it immediately starts to absorb heat from its surroundings (the boiling water). Since, the heat provided by boiling water is so high, it is very easy for the ice cube to melt. The phase change of ice to water requires a lot less energy to start and continue than the energy for the phase change of water to steam.
A process which requires less energy to occur will happen faster in nature. This is almost obvious since the most important prerequisite of undergoing a process or a reaction is to get the energy to start it. If the energy requirement is low, it will happen faster.
Hence, all the heat energy is absorbed very fast and easily by the ice cube during the phase change from ice to water and during that time the water in the container stops boiling to provide heat to the more spontaneous process that is melting of the ice cube.
Hence, option C) is correct.

Note: Ice is less dense than water, so there is no chance that the ice cube will sink to the bottom of the container. Hence options A) and D) are inherently incorrect.
As explained above, the process of melting is more favored and during this process, boiling stops. So option B) becomes incorrect.
Also, since the mass of the ice cube is much lower than that of the boiling water (one-tenth), the ice cube will start to melt almost instantaneously and no boiling (and hence no bubbles will be formed) will take place. So, option E) also becomes incorrect.