Density and Freezing Properties

• High density due to H-bonds; most organisms have a high percentage of water and so a similar density to an aquatic habitat, so float and density changes cause currents that circulate nutrients
• Water density lowers as temperatures fall below 4°C (max density); temperature at the pond’s bottom providing a safe non-frozen habitat, ice forming at 0°C has the lowest density and so floats
• Ice has a lower density; as water expands when it freezes as slow-moving molecules allow the max H-bonds to form, this pushes molecules apart and creates a crystal lattice
• Floating ice is good for aquatic organisms as it thermally insulates the water below, so they don’t freeze it (its also a habitat itself) large energy loss required to change liquid water to ice making it less likely