Water Flashcards
What is the structure of water
- 2 hydrogen atoms covalently bonded to 1 oxygen atom
- Polar molecule
- 2 charged regions makes it dipolar
Why is water a polar molecule?
Each hydrogen shares a pair of electrons with the oxygen
- Oxygen is more electronegative so it pulls the electrons closer
- Water has an unevenly distributed charge
- This makes the oxygen slightly negative and the hydrogens slightly positive
- This creates 2 charged regions making water a polar molecule and its diplolar
Hydrogen bonds in water
-Water forms hydrogen bonds between the oxygen on one water molecule and the hydrogen on the other
-Numerous hydrogen bonds in water make it a very stable structure
What are the 4 main roles of water
- Support
- Temperature Regulation
- Solvent
- Metabolic Reactions
Support - Internal
Strong cohesive forces
Cohesion = Water molecules sticking together by hydrogen bonds
-Strong cohesive forces due to hydrogen bonds maintains water columns in xylem —> water transported from roots to leaves
- Water molecules stick together so during transpiration, water can move up in columns
Support - Internal
Not easily compressed
- Water isn’t easily compressed so it can provide support in non woody plants via turgor pressure
and in some animals e.g hydrostatic skeleton in earthworms
Support -external
- Strong cohesive forces between molecules due to hydrogen bonding produce surface tension where water meets air
- Enables insects to walk on the surface of water e.g pond skater
- Water provides buoyancy for aquatic organisms e.g whales
Cohesion and Hydrogen bonds
-Hydrogen bonds form between H2O molecules due to attraction between slightly negative oxygen and slightly positive hydrogen
- Cohesion = attraction between molecules of the same type
- Molecules with strong cohesive forces like to stick to eachother
- Due to many hydrogen bonds water is a cohesive molecule
What is specific heat capacity?
The heat energy required to raise the temperature of 1kg of an object or a substance by 1°
What is specific latent heat?
Latent heat = the heat energy required to change the state of 1kg of a substance of a material without changing its temperature
What is latent heat of vaporisation?
= The heat energy required to boil or condense the material at its boiling point
Temperature regulation
High heat capacity
- Absorbs a lot heat energy before increase in temp due to hear being absorbed by hydrogen bonds
—> buffers temp changes - Minimises temp increases in cells due to biochemical reactions (enzymes)
- Help prevent dangerous fluctuations in temp in aquatic habitats
Temperature Regulation
Latent heat of vaporisation
- A large amount of thermal energy must be absorbed by water to break the hydrogen bonds and evaporate
- Only a little water is required to evaporate for the organism to lose a great amount of heat
(energy required to break H bonds) - cooling effect - Helps maintain constant body temp
—heat energy removed from body to evaporate - sweat
— has a cooling effect in plants via transpiration
Solvent
Water is the universal solvent due to it being polar
Metabolites can be transferred efficiently
Transport of nutrients eg glucose in blood and sucrose in phloem of plants
Removes excretory products
Used a medium for metabolic reactions
Metabolic Reactions
A metabolite is a substance necessary for metabolism
Metabolite - involved in reactions eg condensation and hydrolysis
Solvent -> metabolic reactions occur in it
