The question on one of my assignments says, "Explain why a thick layer of ice on the lake can support the weight of a person, but the liquid water cannot." I would assume it's because solids are solid and liquids are liquid, but I feel like they want a more scientific answer. Is it because ice has a lattice structure that locks the molecules in place, whereas the water molecules in liquid water are more easily displaced?

Answer 1

in addition to being solid, ice floats

the added buoyancy helps to support a person's weight

Answer 2

Yes, of course it has to be solid.
Also: The weight of water displaced by the ice when you stand on it must be at least as much as the weight of the ice floe plus your weight. That defines how big the rigid chunk of ice has to be (assuming you are far from shore in deep water). If you break it into little chunks, down you go.

Answer 3

Personally I think the question is a poor one. I think your answer is good for that type question AND I think your first answer is good also and your reasoning that something else is needed is right on. Another way is to say that molecules in solids are not easily displced but the molecules in liquids are. You can drive a nail, for example, into a solid piece of wood but it requires much more force to do that than to force a nail into a liquid surface.

Answer 4

If this question is asking about the intermolecular force, the ice have stronger intermolecular force that make the water particles to stay together.