Water (Cambridge (CIE) AS Biology): Flashcards
Exam code: 9700
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Why is water a good solvent, and why does this matter to organisms?
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Why is water a good solvent, and why does this matter to organisms?
Water is polar, so it dissolves ions and polar molecules.
This allows substances to be transported and to react in solution.
Why is water's high specific heat capacity important for living organisms?
It resists changes in temperature.
This keeps aquatic habitats and internal body temperatures stable.
Why is water's high latent heat of vaporisation useful?
A lot of heat energy is needed to evaporate water.
So evaporation (e.g. sweating) removes a lot of heat, providing effective cooling.
Water's high heat capacity means it resists changes in temperature.
Water's high specific heat capacity means it resists changes in temperature.
True or False?
Water's high latent heat of vaporisation makes it useful for cooling by evaporation.
True.
Evaporating water absorbs a large amount of heat, cooling the organism.
Why is a water molecule polar?
Oxygen is more electronegative than hydrogen.
So the oxygen is slightly negative (δ–) and the hydrogens are slightly positive (δ+).
How do hydrogen bonds form between water molecules?
The slightly positive (δ+) hydrogen of one water molecule is attracted to the slightly negative (δ–) oxygen of another.
This attraction is a hydrogen bond.
Define hydrogen bond.
A hydrogen bond is a weak attraction between a slightly positive hydrogen and a slightly negative atom (e.g. oxygen) of another molecule.
Water is a molecule, with a slightly negative oxygen and slightly positive hydrogens.
Water is a polar molecule, with a slightly negative oxygen and slightly positive hydrogens.
True or False?
A single hydrogen bond is strong compared with a covalent bond.
False.
An individual hydrogen bond is weak, but large numbers of them together give water its special properties.
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