ZIMSEC O Level Biology Notes:Properties and Biological significance of water

Property: High heat of fusion

  • This is a measure of the heat energy required to melt a solid (ice).
  • Liquid water must lose a large amount of heat energy to freeze.

Biological role

  • Contents of cells and their environment are therefore less likely to freeze.
  • This is an advantage for bodies of living organisms and organisms that live in water.

Property: Density and freezing

  • The density of water decreases below 4°C and ice tends to form on top and floats.
  • Since ice floats, it forms at the top first and at the bottom last.

Biological role

  • Ice insulates the water below it, thus increasing the chances of survival of organisms in water.
  • It also helps maintain circulation in large bodies of water (water expands and rises at 4°C).

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