Final answer:
The buoyant force on a submerged block of ice equals the weight of the displaced water, due to ice having a lower density than liquid water. This property also explains why ice can exert significant expansion forces, capable of fracturing strong materials.
Step-by-step explanation:
When a block of ice is completely submerged in liquid water, it experiences a buoyant force equal to the weight of the water displaced by the ice. As ice is less dense than water due to hydrogen bonds causing water molecules to expand and occupy more space when frozen, a block of solid ice will displace an amount of water that weighs more than the ice itself. This is why ice floats on water.
The buoyant force acting on a submerged block of ice is equal to the mass of the displaced liquid water multiplied by gravity. The phenomena of ice being less dense as a solid than as a liquid is a unique characteristic of water and is essential for supporting aquatic life during winter. It ensures that bodies of water do not freeze solid from bottom to top, allowing organisms to survive beneath the surface, in the liquid water.
Considering ice's expansion upon freezing, it is not surprising that the forces resulting from this expansion can fracture containers such as bottles, boulders, and even engine blocks if they are not able to accommodate the increased volume of ice compared to water.