Ice and water: what changes?

Correct answer: Its density is lower than that of liquid water.

Ice floats because its density is lower than that of liquid water, not simply because it is a solid. The claim does not extend to every other liquid.

Evidence: Ordinary ice floats because it is less dense than liquid water. The key fact at the top of the reading compares the density of ice with that of liquid water.

Correct answer: Hydrogen bonding holds the molecules in a more open crystal structure.

Freezing produces a more open crystal structure. That is different from the molecules growing or some mass disappearing.

Evidence: On freezing, these interactions hold the molecules in a more open crystal structure. The previous sentence identifies hydrogen bonds, and the next paragraph compares equal masses under ordinary atmospheric pressure.

Correct answer: The ice has less mass.

At equal volume, lower density means less mass. Ordinary ice is less dense than liquid water, so the ice has less mass.

Evidence: For equal volumes of ordinary ice and liquid water, the ice has less mass. The comparison uses material volumes, not the gaps between separate ice cubes.