Syllabus Edition
First teaching 2023
First exams 2025
Gerridae lacustris, more commonly known as pond skaters, are able to rest on the surface of a pond.
Which of the following properties of water enables this?
Ability to hold a lot of heat
Ability to form hydrogen bonds
Less dense when frozen
Colourless and odourless
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Plants transport water against the force of gravity up the xylem to provide leaves and flowers with water.
Which bonds hold water to the surface of the xylem?
Cohesive
Ionic
Covalent
Hydrogen
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During winter when temperatures drop below freezing (0 °C), fish are able to survive in lakes.
Why is this possible?
Fish use energy from food to increase their body temperature.
The sun warms stones on the lake floor which then heat the water.
Fish can produce an enzyme that stops their blood from freezing.
Ice on the surface of the lake insulates the water below.
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The specific heat capacity of water is the highest of all liquids.
Which of the following is a correct definition of specific heat capacity?
The heat required to change one mole of liquid into one mole of gas.
The heat required to raise the temperature of 1 kg of liquid by 1 °C.
The heat required to change one mole of solid into one mole of liquid.
The ability of a solid to transfer heat to a liquid.
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Which of the following properties of water are a result of intermolecular forces?
1 and 2
1, 2 and 3
1,2 and 4
All
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Which of the following properties of water stops enzymes in leaves from being denatured during transpiration?
|
1
|
water retains a lot of heat
|
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2
|
water forms hydrogen bonds with other polar and non-polar molecules
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3
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a lot of heat is required to evaporate water
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4
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water is cohesive
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1 only
1 and 2
2, 3 and 4
3 only
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Water counts for about 70% of the mass of living organisms.
Why is water essential for living organisms?
It is more dense as a solid than a liquid.
It is used in condensation reactions to synthesise macromolecules.
Globular proteins and monosaccharides can dissolve in it.
It only requires a small amount of energy to raise its temperature.
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Which property of water is paired with an incorrect physiological use?
| property | use | |
| A | forms hydrogen bonds between water molecules | dissolves metabolites within cells |
| B | is a polar molecule | dissolves ionic molecules required in signalling |
| C | has a high specific heat capacity | optimum enzymatic activity is maintained |
| D | has a high latent heat of vapourisation | enables heat loss through sweating |
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Sodium hydrogen carbonate (NaHCO3) dissociates into sodium ions (Na+) and bicarbonate ions (HCO3-) when it is dissolved. The latter creates an alkaline environment, suitable for enzymes, and bicarbonate ions in the blood, which help to buffer lactic acid during exercise.
How does water help the production of bicarbonate ions?
The oxygen atoms form ionic bonds with bicarbonate ions
The oxygen atoms in water attract bicarbonate ions
The hydrogen atoms for hydrogen bonds with bicarbonate ions
The hydrogen atoms in water attract bicarbonate ions
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Which of the following does not rely on the specific heat capacity of water?
Heat loss through evaporation of sweat
Enzyme function
Aquatic ecosystems withstanding extreme temperature change
Humans living in sub-zero temperatures
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Enzymes are soluble proteins that use their specific shape to catalyse biological reactions.
What is most likely to happen to the rate of reaction if an enzyme is dissolved in a
non-polar solvent such as hexane (C6H14)?
The rate of reaction will stay the same
The rate of reaction will increase
The rate of reaction will decrease
The enzyme will precipitate out of solution
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When ice on the surface of a pond melts, minerals rise to the surface.
Which properties of water cause this?
1 and 2 only
1 and 3 only
1 and 4 only
All
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