water Flashcards
part of biological molecules
what are polar molecules?
molecules that have regions of negativity and regions of positivity
what group in water molecules, makes them polar?
the hydroxyl group
how strong are hydrogen bonds?
they’re weak interactions which break and reform between constantly moving water molecules
even though hydrogen bonds are weak, what makes them strong sometimes?
the fact that they occur in high numbers
what gives water its unique characteristics?
hydrogen bonding
what type of intramolecular bonds are in water molecules?
polar covalent bonds
what is water’s boiling point like?
it’s unusually high
why is water’s boiling point the way it is and why is it liquid at room temperature, even if its a lighter molecule than oxygen?
- because of the hydrogen bonding between water molecules.
- lots of energy is needed to increase water temperature and cause it to evaporate
what happens to water when it turns into ice in terms of weight?
it becomes less dense
why does water have its unusual property as ice?
- because as water is cooled, the hydrogen bonds fix the positions of the water molecules further apart than in the liquid state
- this produces a giant, rigid but open structure, with every oxygen atom at the centre of a tetrahedral arrangement of hydrogen atoms, resulting in a solid that’s less dense than liquid water.
- so, ice floats
what properties of water allow water to move as one mass? give an example of where this happens?
- cohesion and adhesion
- plants are able to draw water up their roots
what are water molecules more strongly cohesive to? what does this result in?
- to each other rather than the air
- results in water having a ‘skin’ of surface tension
since water is a polar molecule, what can it act as?
a solvent in which many solutes in an organism can be dissolved
give an example in cells, where water is vital as a solvent?
- the cytosol of bacterial prokaryotes and eukaryotes is mainly water.
- many solutes are also polar
- water acts as a medium for chemical reactions and also helps transport dissolved compounds into and out of cells
what does water’s adhesion and cohesion lead to? what does this make it?
- capillary action
- an efficient transport system in living things
what is water’s role in living things in terms of temperature?
- water acts as a coolant helping to buffer temperature changes during chemical reactions in cells, because of the large amounts of energy needed to overcome hydrogen bonding
why is it important to maintain constant temperatures in cellular environments?
because enzymes are only active in a narrow temperature range
how is water important for fish as a habitat?
- water is a stable environment, it doesnt change temperature or vaporise easily = constant environment
how does ice help fish in ponds?
- because ice floats, it forms an insulating layer on top of the water
explain how hydrogen bonds form (3 marks)
- Oxygen and hydrogen share electrons unequally when they bond.
- Oxygen is more negative & Hydrogen is more positive
- The more negative oxygen atom on one molecule is attracted to the more positive hydrogen atom
Why is water a polar molecule? (2 marks)
- In water the bonds between oxygen and hydrogen involve unequal sharing of electrons
- resulting in the oxygen atom being more negative and the hydrogen atoms being more positive.
which properties of water make it an important component of blood and why? (3marks)
- water is a liquid = transport medium
- polar solvent and (many) biological molecules are polar , so better at dissolving them
- coolant = more resistant to temperature change
Water forms the basis of Stroma in chloroplasts and the matrix in mitochondria. which properties of water make it an important component of these organelles?
- water is liquid = allows movement of substrates and enzymes
- movement of these is necessary for reactions to occur
- water is a polar solvent and substrates / enzymes are, polar.
- water is substrate for some reactions
