Q1/3 W2 Density of Water

Click the plus sign to learn about why ice floats

Click the plus sign to learn what density is

Click the plus sign to learn about how the temperature of water affects its density

Why Ice Floats

Ice floats because it is less dense than liquid water. When water freezes, hydrogen bonds hold the molecules in a rigid lattice that spreads them farther apart, making ice take up more space than the same mass of liquid water. This lower density allows ice to float on the surface.

The temperature of water affects how closely the molecules are packed.

• Gaseous water (steam/vapor): the warmest form of water; molecules move very fast and are far apart → least dense
• Warm water: molecules move quickly and are more spread out → less dense
• Room temperature water: molecules are closer together than warm water → moderate density
• Cold water: molecules move slower and are packed more tightly → more dense
• Freezing water (ice): hydrogen bonds form a rigid lattice, spacing molecules farther apart → less dense than liquid water, which is unusual because most solids are denser than their liquid forms

Density

Density is a measure of how much mass is packed into a given volume (how tightly atoms/molecules are packed together).