Properties of Water

What are the 5 key properties of water?

• High specific heat capacity

• High latent heat of vaporization

• Cohesion

• Metabolite

• Solvent

What is a metabolite?

A substance that is involved in a chemical reaction as a reactant or as a product

What is a solvent?

A substance capable of dissolving another substance (the solute)

What is high specific heat capacity?

When a lot of energy is required to raise the temperature of a substance

What is high latent heat of vaporization?

When a lot of energy is required to evaporate a substance

What is cohesion?

When one water molecule “sticks” to the next via hydrogen bonding

Give and describe two animal processes which water is used as a metabolite

• Digestion → Hydrolyses bonds between amino acids of insoluble proteins → Molecules are now soluble and can be absorbed

• Respiration → ATP is immediate energy source for cells → ATP is hydrolysed to release energy for the cell’s activities: ATP + H2O → ADP + Pi (+ energy)

What are the 3 uses in organisms of water being a solvent?

• Transport (e.g: blood plasma is mainly water with glucose, ions, CO₂ and urea dissolved in it)

• Medium (dissolved substances in water are free to move around and react with other molecules)

• Excretion (Water is used to dissolve substances which are excreted from the body. e.g: urine contains urea and excess ions)

What kind of substances can water dissolve

Polar/charged (hydrophilic)

Give and describe the two benefits for living organisms of water having a high specific heat capacity

• Buffers temperature changes in habitats → temperature where aquatic organisms live does not change rapidly

• Buffers internal body temperature changes → makes thermoregulation easier → temperature control is important for maintaining optimum temperature for enzymes to act at

Give and describe the two benefits for living organisms of water having a high latent heat of vaporization

• Transpiration of water cools plants → evaporation and loss of water through the leaves

• Large amount of heat energy removed from skin and blood within the skin capillaries → energy used to evaporate sweat → large cooling effect → cooling prevents temperature rises which could lead to enzymes denaturing

Give and describe the two benefits for living organisms of water being cohesive

• Allows for bulk transport of substances down pressure gradients (e.g: mass flow in xylem)

• Creates surface tension (as top molecules do not have any molecules above that they are attracted to, so a downward attraction is produced) enabling small animals to walk on the surface of water