An ice cube is put into a heated pan. What will most likely happen to the molecules in the ice as the ice is heated?

• A. The molecules will begin to move slower.
• B. The molecules will begin to move faster.
• C. The molecules will being to increase in density.
• D. The molecules will begin to condense in the air.

Answer: (B)

When heat is added, energy goes into the ice and increases the average kinetic energy of its molecules. That means the water molecules start vibrating and moving more rapidly within the solid structure. As more energy is absorbed, these movements become even greater, and the ice will eventually melt as the bonds holding the solid lattice weaken. So, the best description of what happens to the molecules as the ice is heated is that they begin to move faster. The ideas that they would move slower, become more dense, or condense in the air don’t line up with adding heat to a solid.