Describe four properties of water that are due to hydrogen bonding and polarity.

Describe how water is carried through a flowering plant.

Some of the water carried to the leaves of a plant is used in photosynthesis. Explain the role of water in the light-dependent reactions of photosynthesis.

Descriptions of properties expected not lists of properties.

hydrogen bonding:
a. high specific heat capacity requiring large amounts of energy to break the H-bonds/to raise the temperature;
b. boiling point is high/100°C as H-bonds must be broken to change from liquid to gas;
c. cooling effect of evaporation due to H-bonds taking energy from liquid water to break / high latent heat of evaporation;
d. water molecules on surface resistant to forces because of surface tension;
e. water is most dense at 4°C due to more regular hydrogen bonding;

polarity:
f. water molecules stick together through cohesion; (full idea required)
g. water molecules stick to other polar molecules through adhesion; (full idea required)
h. good solvent of polar organic molecules

a. active transport of solutes from soil into roots;
b. draws water by osmosis
c. root hairs provide a large surface area for water uptake;
d. carried through xylem vessels;
e. transpiration is the loss of water (vapour) from leaves and stems / stomata;
f. (transpiration) creates suction/pull/negative pressure;
g. cellulose wall with rings of lignin give strength to resist (low) pressure;
h. water pulled up due to capillary action/cohesion/adhesion;
i. continuous column of molecules/transpiration stream;

a. water only plays a role in non-cyclic photophosphorylation;
b. chlorophyll absorbs light/photons and activates electrons of photosystem II;
c. excited/active electrons of photosystem II are passed to carriers;
d. photolysis is the splitting of water;
e. produces O₂ and H⁺/proton and electrons;
f. O₂ released (as waste);
g. electrons (from water) replace lost electrons in photosystem II;
h. electrons from photosystem II pass (through carriers) to photosystem I;
i. electrons from photosystem I pass to NADP⁺ (in stroma);
j. NADP⁺ accepts H⁺/proton (from water) to form NADPH;
k. electron flow causes protons pumped across thylakoid membranes/into the thylakoid space;
l. creating a proton concentration gradient;
m. chemiosmosis couples electron transport to ATP synthesis;
n. protons pass through ATP synthase/synthetase;
o. NADPH/H⁺/proton is passed to the light-independent reactions (to fix carbon);

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7a, few completely related hydrogen bonding to surface tension. In discussing solvent properties, a number neglected to draw in that water performed best at dissolving polar substances. When discussing adhesion, students should have referenced the polarity of molecules.

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In part b, many referenced the role of xylem. Many used terminology correctly in this section making reference to transpiration pull, cohesion, adhesion and the transpiration stream. The stages of water uptake that occur in the root was covered in less detail and with less accuracy in general.

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Part c was in general poorly done as the question required students to discuss the role of water. The details of photolysis were often excluded as were the correct details of chemiosmosis.