AP BIOLOGY

Detailed explanation-1: -Water molecules spread out when they are bonding into a solid crystalline structure. This spreading-out action leads ice to be less dense than liquid water, causing ice to float. This spreading-out action of the water molecules during freezing also means that applying pressure to water lowers the freezing point.

Detailed explanation-2: -The expansion upon freezing comes from the fact that water crystallizes into an open hexagonal form. This hexagonal lattice contains more space than the liquid state.

Detailed explanation-3: -As water freezes it expands. So, ice has more volume (it takes up more space, but has less density) than water. Share with the children that this is a very special property of water.

Detailed explanation-4: -Point out that when water freezes, the water molecules have slowed down enough that their attractions arrange them into fixed positions. Water molecules freeze in a hexagonal pattern and the molecules are further apart than they were in liquid water. Note: The molecules in ice would be vibrating.