3.1.7 - Water

Thursday 23rd November ‘23

Cohesion

• Tendency to stick together due to hydrogen bonds between molecules.

  • Allows long columns of water to travel in xylem tubes.

• Causes surface tension where water meets air.

  • Allows the surface of water to be a habitats (EG for insects such as pondskaters).

Metabolic Reactions

• Water is a reactant in many reactions. EG hydrolysis + photosynthesis.

• Water is a product in many reactions. EG condensation + aerobic respiration.

High Latent Heat of Vaporisation

• It takes lots of energy to evaporate water.

• Organisms can cool themselves without losing lots of water. EG sweating where the transfer of heat energy allows organisms to cool down.

High Specific Heat Capacity

• Lots of energy required to change temperature of water. When we heat it, ______________ goes towards weaking or breaking _____________, instead of ___________________. This allows water to act as a _________ against rapid temperature change.

• This allows water to act as a ____________ for ______________.

Density

• Ice is less dense than water so the ice floats and ____________ the water below.

• Organisms can continue to live in the water under the ice.

Solvent

• Lots of substances can dissolve in water.

• Both eukaryotic and prokaryotic cells contain a large amount of dissolved substances. EG chemicals involved in ____________ reactions and enzymes.

  • Bodies of water contain dissolved oxygen which is used by the organisms for _____________, making an excellent habitat.

• Can be used to ______________ substances.

  • Blood plasma which contains carbon dioxide, minerals (eg sodium) ions and chemicals (eg glucose + amino acids).

  • Water in ________ vessels contains dissolved mineral ions (EG _______________ ions which pass into roots from soil → leaves where they make chlorophyl for photosynthesis).