water Flashcards
describe the structure of water
molecule of water haas one atom of oxygen joined to two atoms of hydrogen by shared electrons,
shared negative hydrogen electrons are pulled towards the oxygen atom, the other side of each hydrogen atom is left with a slight positive charge.
The unshared negative electrons on the oxygen atom give it a slight negative charge
this makes water a polar molecule, it has a partial negative (§-) charge on one side and a partial positive (§+) charge on the other.
The slightly negatively charged oxygen atoms attract the slightly positively charged hydrogen atoms of other water molecules
This attraction is called hydrogen bonding and
slightly positively charged side
it gives water some of its useful properties.
what is a polar molecule
a polar molecule, has a partial negative (§-) charge on one side and a partial positive (§+) charge on the other.
what is hydrogen bonding?
when the slightly negatively charged oxygen atoms attract the slightly positively charged hydrogen atoms of other water molecules
state five properties of water that make it useful for living organisms
Water has a high specific heat capacity
High latent heat of evaporation
Very coursive
Good Solvent
Less dense when it’s solid
What is high specific heat capacity and how does water have it?
Specific heat capacity is the energy needed to raise the temperature
The hydrogen bonds between water molecules can absorb a lot of energy.
So water has a high specific heat capacity - it takes a lot of energy to heat it up.
This means water doesn’t experience rapid temperature changes, which is one of the properties that makes it a good habitat - the temperature under water is likely to be more stable than it is on land
What is high latent heat of evaporation and how does water have it?
It takes a lot of energy to break the hydrogen bonds between water molecules
So water has a high latent heat of evaporation - a lot of energy is used up when water evaporates.
useful for living organisms because it means water’s great for cooling things. some mammals sweat when they’re too hot. When sweat evaporates, it cools the surface of the skin.
how is water cohesive?
Cohesion is the attraction between molecules of the same type
Water molecules are very cohesive because they’re polar.
This helps water to flow, making it great for transporting substances also helps water to be transported up plant stems in the transpiration stream
How is water a good solvent?
lot of important substances in biological reactions are ionic this means they’re made from one positively-charged atom or molecule and one negatively-charged atom or molecule
Because water is polar, the slightly positive end of a water molecule will be attracted to the negative ion, and the slightly negative end of a water molecule will be attracted to the positive ion.
This means the ions will get totally surrounded by water molecules, they’ll dissolve.
How is water less dense when it’s solid?
At low temperatures water freezes - it turns from a liquid to a solid.
Water molecules are held further apart in ice than they are in liquid water because each water molecule forms four hydrogen bonds to other water molecules, making a lattice shape. This makes ice less dense than liquid water - which is why ice floats.
This is useful for living organisms because, in cold temperatures, ice forms an insulating layer on top of water - the water below doesn’t freeze. So organisms that live in water, like fish, don’t freeze and can still move around.
