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?
in addition to being solid, ice floats
the added buoyancy helps to support a person's weight
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.
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.
If this question is asking about the intermolecular force, the ice have stronger intermolecular force that make the water particles to stay together.
You're on the right track! The reason why a thick layer of ice can support the weight of a person while liquid water cannot is indeed due to the difference in the molecular structure of ice and liquid water.
To provide a more scientific explanation, we need to understand the structure of water molecules. Water is made up of two hydrogen atoms and one oxygen atom, forming a molecule with a bent shape. These molecules are held together by hydrogen bonds, which are relatively weak interactions between the positively charged hydrogen atoms and the negatively charged oxygen atoms in neighboring water molecules.
In liquid water, the molecules are in constant motion, which means that they are constantly breaking and forming hydrogen bonds with neighboring molecules. This mobility of the water molecules allows them to flow, giving water its liquid state. However, this constant movement also means that the water molecules can't maintain a well-defined structure, which is why liquid water cannot support the weight of a person.
On the other hand, when water freezes and forms ice, the temperature drops below the freezing point, causing the molecules to slow down. As a result, the hydrogen bonds between water molecules become more stable. In fact, the water molecules arrange themselves in a hexagonal lattice structure in ice, with each molecule being surrounded and locked into place by neighboring molecules. This lattice structure gives ice its solid and rigid nature.
The stability and organization of the ice lattice make it much more resistant to external pressure or forces. That's why a thick layer of ice can support the weight of a person, as the interlocking network of water molecules in the ice lattice distributes the load across a larger area, minimizing the pressure exerted on individual molecules.
In summary, the difference in the molecular structure of ice and liquid water is what allows ice to support the weight of a person while liquid water cannot. The ice's lattice structure locks the water molecules in place, making it solid and rigid, while the constant movement of water molecules in the liquid state prevents it from maintaining a stable structure to bear weight.