Question

iii) name the type of bond that forms between the alcohol in a water molecule.

1. figure 3.1 shows how the dissolved oxygen concentration changes with depth in a tropical ocean.

a) explain why dissolved oxygen concentration is high in the surface waters of the ocean
______
______ (1)
b) name the zone between 200m and 400m. ______ (1)

1. figure 4.1 shows a cross - section of an ocean

on fig. 4.1, name features p, q, and r.

Explanation:

For question 3a: Surface ocean waters have high dissolved oxygen because of gas exchange with the atmosphere (diffusion of O₂ from air into water) and photosynthesis by phytoplankton (which produce O₂).
For question 3b: The zone between 200m and 400m in the ocean, where dissolved oxygen drops rapidly, is the oxygen minimum zone (or the mesopelagic zone's oxygen - depleted part, more specifically the oxygen minimum layer which often occurs in the thermocline/transition zone around these depths).
For question 4 (naming ocean features):

• Feature P: Likely a seamount or volcanic island (a mountainous structure rising from the ocean floor, with the top above or near the surface).
• Feature Q: A hydrothermal vent (structures on the ocean floor that emit hot, mineral - rich water, often found on abyssal plains or near mid - ocean ridges).
• Feature R: A continental slope (the steeply sloping area between the continental shelf and the abyssal plain).

Answer:

3a) High dissolved oxygen in surface ocean waters is due to gas exchange with the atmosphere (O₂ diffuses from air into water) and photosynthesis by phytoplankton (which produce O₂).
3b) The zone between 200m and 400m is the oxygen minimum zone (or part of the mesopelagic zone with low oxygen).

1. P: Seamount (or Volcanic Island); Q: Hydrothermal Vent; R: Continental Slope.