Final answer:
When ice melts, the volume of water decreases, but the mass of water remains the same. The decrease in volume is due to the way water molecules arrange themselves during the phase change.
Step-by-step explanation:
When ice melts, the volume of water is smaller than that of the ice, but the mass of the water is the same as the mass of the ice. This is because mass is a conserved property, meaning it is not created or destroyed in a chemical or physical change. The decrease in volume when ice melts is due to the way the water molecules align themselves when transitioning from a solid to a liquid state.
During melting, the water molecules break free from their fixed positions in the ice lattice and gain more freedom to move around. This causes the water molecules to arrange themselves in a way that takes up less space, resulting in a decrease in volume.
However, the number of water molecules remains the same, so the mass does not change. The mass of the water is equal to the mass of the ice because the composition of the constituent molecules (11.19% hydrogen and 88.81% oxygen by mass) is the same in both states.