Final answer:
The density of ice at 0°C is 917 kg/m³ according to the PhET Density lab. Ice has a lower density than water due to hydrogen bonding, causing it to expand when freezing.
Step-by-step explanation:
The density of ice at 0°C is 917 kg/m³ according to the PhET Density lab. This means that one cubic meter of ice has a mass of 917 kilograms. Ice has a lower density than water because it expands when it freezes due to hydrogen bonding, causing water molecules to be spaced farther apart in ice compared to liquid water.