Video Transcript
Which of the following sequences of statements correctly describes why ice floats on water? (A) 1, (B) 2, (C) 3, (D) 4, or (E) 5.
The question asks why ice floats on water. Ice is formed when water is cooled. When water cools down to below four degrees Celsius, the water molecules form large hexagonal crystals due to the formation of more hydrogen bonds. When the liquid freezes at zero degrees Celsius, forming ice, these large hexagonal crystals are fully formed. The hydrogen bonds are long and push the molecules apart, causing an expansion. Therefore, the ice has a greater volume than liquid water. Although the volume increases, there is no change in mass as nothing is actually added to the water.
The water molecules are just arranged differently and are further apart. As the mass remains the same and the volume increases and density is calculated by dividing mass by volume, the density decreases. It is the fact that ice is less dense than water that allows it to float on water.
So, to recap, when water freezes, it becomes ice. As it freezes, it expands. The ice has a greater volume but the same mass. This makes the ice less dense than water. Therefore, the sequence of statements that correctly describes why ice floats on water is (A), 1.
