Final answer:
Ice is the term for water that has frozen and become solid. It is less dense than liquid water, allowing it to float and create an insulating layer on bodies of water. While snow, frost, and hail are also solid states of water, they form under different conditions than typical ice.
Step-by-step explanation:
Water that has frozen and become solid is called ice. Ice is formed when liquid water (H₂O) freezes, a process that is a physical change since the composition of the molecules remains the same, with 11.19% hydrogen and 88.81% oxygen by mass. This transformation occurs because water has the unique property of being less dense as a solid than as a liquid due to its shape, polarity, and hydrogen bonding. As a result, ice floats on the surface of bodies of water, providing an insulating layer that helps to protect aquatic life during winter months.
While snow and frost are also solid forms of water, snow is specifically made up of ice crystals and requires a significant amount of heat to be extracted from the air for the phase change from water vapor to solid. Frost forms when water vapor changes from a gas directly to a solid, and hail is precipitation that freezes into chunks of ice before falling to the ground.