2.4 Water and its functions Flashcards
What is the dipolar water molecule
.Water is made of two atoms of hydrogen and one atom of oxygen
. Molecule has no overall charge, but oxygen has a slight 2- charge and the hydrogen atoms have 1+ charges
So water has both positive and negative charges so is dipolar
How does hydrogen bonding occur in water
. The positive 1+ charges of hydrogens in water and the negative 2- oxygen in water make different poles in the molecule.
Because the poles are different charges they attract, so the positive pole of one water molecule is attracted to the negative pole of another water molecule
. This attraction is called a hydrogen bond
Strength of hydrogen bonds
Each bond is weak, but together they form important forces that cause the water molecules to stick together, giving water unusual properties
Why is the boiling point of water higher than expected
. Water molecules stick together so more energy is needed to separate them the would be needed if they didn’t bond to each other
. Without hydrogen bonding water would be a gas
So this is why the boiling point of water its higher than expected, and if it was a gas, life on earth wouldn’t be as we know it
Why does water have a high specific heat capacity
There Is lots of hydrogen bonding between water molecules so more energy is needed to separate them than if they weren’t bonded together.
This means it takes more energy to heat a given mass of water so it has a higher SHC
Why is it good for water to have a high specific heat capacity
Organisms are mainly made out of water, so this high specific heat capacity protects/buffers them against sudden temperature changes in terrestrial environments/ aquatic environments
What is cohesion (in terms of water)
The tendency of molecules to stick together
Describe the cohesion forces of water
How do these forces effect water in plants
Water has high cohesive forces as it has lots of hydrogen bonding which join the molecules together
These forces allow water to be pulled up through a xylem tube/vessel in plants
How does surface tension impact water in a body of water
. Where water molecules meet air, they tend to be pulled back to the body of water rather than escaping from it.
So the water surface acts as a skin and is strong enough to support small organisms such as pond skaters
Describe the latent heat of vaporisation of water
Why is this good for mammals
It is high
There is lots of hydrogen bonding in water so a lot of energy is required to evaporate 1g of water
As a result sweating in mammals is a good way of cooling because body heat/ energy is used to evaporate the water
Why is water important to living organisms
Water is the main constituent of all organisms, up to 65% of mammals are made of water
Water is where life on earth evolved from, and is the environment where many still life
The role of water in metabolism
. Water breaks down complex molecules in the body by hydrolysis eg proteins to Amino acids
Water is also released In condensation reactions
.Chemical reactions take place in an aqueous medium
.Water is a major raw material in photosynthesis
How is water a solvent
. Water dissolves other substances:
. Gases eg carbon dioxide and oxygen
. Wastes such as ammonia and urea
. Inorganic ions and small hydrophilic molecules eg amino acids , monosaccharides
. Enzymes where reactions take place in solution
How does water provide support
Give examples
It isn’t easily compressed
Eg turgor pressure in herbaceous plants, or hydrostatic skeleton of animals eg earthworm
Why is it important for water to be transparent:
In plants and in humans
. Aquatic plants can photosynthesise as light waves can penetrate the water to reach them
. Light can penetrate the jelly like fluid in our eyes front of the retina
