Module 2 Section 2 WATER Flashcards
What are the key functions of water?
1 REACTANT 2 SOLVENT 3 TRANSPORT 4 TEMP CONTROL 5 HABITAT
Describe waters uses as a REACTANT
It’s a reactant in loads of important chemical reactions, including hydrolysis reactions
Describe waters uses as a SOLVENT
Water is a solvent which means some substances dissolve in it. Most biological reactions take place in a solution (eg in cytoplasm) so water is pretty useful
Describe waters uses in TRANSPORTATION
It’s a liquid and a solvent so it can easily transport all sorts of materials that are dissolved into it (eg glucose and oxygen) around plants and animals
Describe waters uses in TEMP CONTROL
It has a high specific heat capacity and a high latent heat of evaporation so it uses up a lot of energy in heating/cooling and evaporation
Describe waters uses as a HABITAT
It helps with temp control, is a solvent and becomes less dense when it freezes- many organisms can survive and reproduce in it
Describe the water molecules structure
One slight negatively charged oxygen atom bonded to two slightly positively charged hydrogen atoms by shared electrons. It is a polar molecule. Water molecules bond together with hydrogen bonds where the oxygen (delta -) has weakly (but high quantity) bonded to the hydrogen (delta +) of another water molecule
What are the 5 properties of water
HIGH SPECIFIC HEAT CAPACITY HIGH LATENT HEAT OF EVAPORATION POLARITY MEANS COHESION POLARITY MEANS GOOD SOLVENT LESS DENSE WHEN SOLID
Explain its HIGH SPECIFIC HEAT CAPACITY
SHC is the energy needed to raise the temp of 1G by 1’c
Hydrogen bonds can absorb a lot of energy, so water has a high SHC
So it doesn’t experience rapid temp changes, meaning it’s a good habitat (temp underwater is likely more stable than temp on land)
Explain its HIGH LATENT HEAT OF EVAPORATION
Takes a lot of energy (heat) to break hydrogen bonds between water molecules, so water has a high LHE
Useful for living organisms as it means it’s a great coolant, which is why some mammals sweat when too hot- sweat evaporates and cools the skin surface
Explain POLARITY MAKING IT COHESIVE
Cohesion is the attraction between molecules of the same type
Water molecules are very cohesive (stick together) because they are polar
Helps it to flow, making it great for transportation of substances. Also helps water be transported up plant stems in the transpiration stream
Explain POLARITY MAKING IT A GOOD SOLVENT
A lot of important substances in biological reaction are ionic- means they’re made from one positively and one negatively charged atom or molecule
The positive end is attracted to the negative ion and vice versa
Meaning the ions will be totally surrounded by water molecules (they dissolve)
Polarity of water makes it useful as a solvent in living organisms (in humans, important ions can dissolve in the blood to be transported around the body)
Explain LESS DENSE AS A SOLID
At low temps water freezes into a solid
Water molecules are held further apart in ice than they are in liquid because each molecule forms 4 hydrogen bonds to other water molecules (lattice structure)- makes ice less dense than water so it floats
Useful for living organisms because in the cold the ice forms an insulating layer on top of water so the rest doesn’t freeze and fish are still free to move (and live)
