Explain how the hydrogen bonding between water molecules gives water a high specific heat capacity, and outline why this property is significant for aquatic organisms.

Water molecules are polar, with a partial negative charge on oxygen and partial positive charges on hydrogen. This polarity allows each water molecule to form hydrogen bonds with neighbouring molecules. A large amount of energy is required to break these hydrogen bonds, so a significant amount of heat energy must be absorbed before the temperature of water rises. This gives water a high specific heat capacity.

Because water heats and cools slowly, the temperature of bodies of water changes only gradually. This thermal stability is important for aquatic organisms: enzyme‑controlled reactions and metabolic processes operate most efficiently at a relatively constant temperature, and rapid temperature changes could denature proteins and disrupt cellular function.