2.4 Water and its functions Flashcards
What are made up of a water molecule?
- two atoms of hydrogen
- one atom of oxygen
What is the overall charge of a water molecule?
0
How is water’s polarity? Why?
Dipolar. Because oxygen is slightly negative and hydrogen is slightly positive.
What is the bonding within a water molecule?
Covalent bonding
What is the bonding between water molecule?
Hydrogen bonding
What are the features of water?
- it is a metabolite in many metabolic reactions
- it is an important solvent
- it has a relatively high specific heat capacity
- it has a relatively large latent heat of vaporisation
- it has strong cohesion and adhesion between water molecules
Explain water’s specific heat capacity.
- water has a high specific heat capacity
- water has a high boiling point and a low freezing point
- it takes a lot of energy to change water’s temperature
- because water molecules stick together, it takes more energy to separate them, break the hydrogen bonds and heat water
- water acts as a buffer against sudden temperature change, this means that the temperature of water tend not to change rapidly
Explain water’s latent heat of vaporisation.
- water has a large latent heat of vaporisation
- a lot of energy is required to break the hydrogen bonds to change water from a liquid to a gas
- organisms can use evaporation of water as a method of cooling and carrying away heat from body without losing too much water at the same time
Explain water’s cohesion and adhesion.
- water has strong cohesion and adhesion because of its hydrogen bonds
- water is able to stick to itself and other molecules
- strong cohesion and adhesion helps water to flow through organisms, carrying substances along with it
- when water molecules meet air, they create a high surface tension (they tend to be pulled back into the body rather than escaping from it)
- by creating a high surface tension, water is strong enough to support small organisms, eg. pond skaters
What are the functions of water?
- solvent
- temperature control
- cooling mechanism
- habitat
- metabolite
- transport
Explain how water can act as a solvent.
- because water is dipolar, this makes lots of substances can be dissolved in water
- the slightly negative oxygens are attracted to the positive ions, whilst the slightly positive hydrogens are attracted to the negative ions
- water dissolves gases, wastes, inorganic ions and enzymes
Explain how water can control temperature.
Because water has a high specific heat capacity, it can act as a buffer against sudden temperature change. This means that the temperature of water tend not to change rapidly.
Explain how water can act as a cooling mechanism.
Because water has a large latent heat of vaporisation, organisms can use evaporation of water as a method of cooling and carrying away heat from body without losing too much water at the same time.
Explain how water can act as a habitat.
Because water has a high specific heat capacity and a high latent heat of vaporisation, it doesn’t change temperature or evaporate easily. This provides a stable environment for many organisms to live in.
However, at low temperature, water freezes and form ice. Ice is less dense than water because water molecules are held further apart in ice. This causes ice to float, forming an insulating layer at the surface of liquid water. This allows organisms to live both on ice and under water.
Explain how water can act as a metabolite.
Water is used during reactions such as hydrolysis, condensation and photosynthesis.
