Question

1. the diagram shows the elements present in two organic molecules, w and x. which molecules could w and x be?

1. what is a consequence of the ability of water to form many intermolecular hydrogen bonds?

a. ice has a higher density than water and floats, providing habitats for fish - eating mammals.
b. light can pass through water, so algae can photosynthesise.
c. some small invertebrates can walk on water surfaces.
d. small amounts of energy are needed to change water from one state to another, so that evaporation rates and condensation rates are rapid.

Explanation:

Question 1

• Monosaccharide: Composed of \(C\), \(H\), \(O\) only. So molecule \(W\) (has \(P\)) cannot be monosaccharide.
• Triglyceride: Composed of \(C\), \(H\), \(O\) only. Molecule \(X\) (has \(N\)) cannot be triglyceride. Molecule \(W\) (has \(P\)) cannot be triglyceride.
• Fatty acid: Composed of \(C\), \(H\), \(O\) only. Molecule \(X\) (has \(N\)) cannot be fatty acid.
• Phospholipid: Composed of \(C\), \(H\), \(O\), \(P\) (and sometimes \(N\)). Molecule \(W\) has \(P\), \(C\), \(H\), \(O\).
• Protein: Composed of \(C\), \(H\), \(O\), \(N\) (and sometimes \(S\) etc.). Molecule \(X\) has \(N\), \(C\), \(H\), \(O\)

• Option A: Ice has a lower density than water (due to hydrogen - bonding in ice creating a more open lattice structure), not higher.
• Option B: The ability of light to pass through water is due to its transparency (related to its molecular structure in terms of electron - cloud and bond types, not hydrogen bonding).
• Option C: The surface tension of water (caused by hydrogen bonding between water molecules at the surface) allows some small invertebrates to walk on water surfaces.
• Option D: A large amount of energy is needed to change water from one state to another (high specific heat capacity, high latent heat of vaporization and fusion) because of hydrogen bonding.

Answer:

C. phospholipid, protein

Question 2