When gallium melts in someone's hand, several changes occur on a microscopic level. Here are the correct responses regarding what happens to the gallium atoms:
1. **The gallium atoms will increase in temperature.** - This is correct, as the heat from the person's hand warms the gallium, raising its temperature.
2. **The gallium atoms will gain kinetic energy.** - This is also correct, as the increase in temperature leads to an increase in the kinetic energy of the atoms, causing them to move more vigorously.
3. **The gallium atoms will gain potential energy, moving freely from each other.** - This is partially correct. As the gallium transitions from solid to liquid, the atoms do gain potential energy that allows them to overcome some of the forces holding them together, allowing them to move more freely.
4. **The gallium atoms will be moving faster on average.** - This is correct. As the gallium melts, the average speed of the atoms increases due to the added energy.
In summary, all the responses mentioned are related to the changes occurring at the microscopic level when gallium melts. However, the most direct implication of melting is that the gallium atoms will gain kinetic energy and move faster on average, which is a key aspect of the phase change from solid to liquid.