Water Flashcards
(14 cards)
What is the structure of water?
H2O is made of 1 oxygen atom (O) joined to 2 hydrogen atoms (H) held together by 2 covalent bonds
oxygen shares one electron with each hydrogen atom while each hydrogen atom shares its one electron with oxygen
Why is water a dipolar molecule?
Shared electrons pulled towards the O2 atom giving the O2 atom a slightly negative charge (δ-) leaving the H+ atoms with a slightly positive charge (δ+)
H2O has both positive and negative poles making it dipolar
How can water molecules form hydrogen bonds?
δ+ hydrogen end of one H2O molecule attracts towards the δ- oxygen end of another molecule creating a force of attraction
What are the 6 main roles of water in living organisms?
- solvent
- temperature control
- cooling mechanisms
- habitat
- metabolite
- transport medium
How does water act as a solvent in living organisms?
Many substances within cells are ionic meaning they consist of + and - ions (e.g salt) and when these ionic compounds are added to H20 ions split apart
H2O is polar so O2- are attracted to the positive ions whilst H+ are attracted to the negative ions
Why is water known as the universal solvent?
It dissolves more substances than any other liquid
Why are water’s solvent properties useful?
- most biological reactions take place in solutions e.g cytoplasms
- dissolved substances can be transported around the body e.g ions
How does water act as a temperature buffer?
H2O has a high specific heat capacity meaning lot’s of energy is needed to raise the temperature of 1 gram of water by 1°C
many H bonds between H2O molecules can absorb a lot of energy before being broken so lot’s of energy needed to break H bonds in water
Why are water’s temperature buffering properties useful?
- resistant to rapid changes in temperature
- allows body to remain at fairly stable temperature
How does water act as a cooling mechanism?
H bonding between H2O molecules means lot’s of energy is needed to evaporate 1 gram of water
means H2O has a high latent heat of vaporisation (boiling point) so lot’s of energy is required to break H bonds to change it from a liquid to gas
Why are water’s cooling mechanism properties useful?
- use H2O evaporation as a method of cooling without losing too much H2O
when H2O evaporates from skin surface, heat energy’s taken away from surface cooling the organism
How does water act as a habitat?
H2O has high specific heat capacity and high latent heat of vaporisation meaning it doesn’t change temperature or evaporate easily providing a stable environment
at low temperatures H2O freezes to form which is less dense than water
Why is water’s habitat properties useful?
- ice floats forming an insulating layer at the surface
- means H2O below layer doesn’t freeze allowing organisms in water to move and survive
How is water a metabolite?
Involved in many chemical reactions inside organisms e.g condensation, hydrolysis and photosynthesis
