7.2 Organisation of an ecosystem

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Question 17
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A student investigated how temperature affects the decay of different fruit juices. During decay, microorganisms break down sugars in the juice to produce organic acids, which lowers the pH of the juice.

The student measured the time taken (in days) for Apple juice, Orange juice, and Grape juice to reach pH 3.5 at different temperatures. Their results are shown in the graph below.

A line graph showing the time taken in days for three different fruit juices to reach pH 3.5 at temperatures from 5 to 30 degrees Celsius. The x-axis is labeled 'Temperature in °C' and has grid lines at intervals of 1 °C, numbered every 5 units from 0 to 30. The y-axis is labeled 'Time taken to reach pH 3.5 in days' and ranges from 0 to 12 days, with main grid lines every 2 days, and smaller grid sub-divisions every 0.2 days. There are three lines representing the different juices: 1. Apple juice (solid line): starts at (5 °C, 8.0 days), drops to (10 °C, 5.0 days), then to (15 °C, 4.0 days), and levels off at (20 °C, 3.0 days), staying flat at 3.0 days up to 30 °C. 2. Orange juice (dashed line): starts at (5 °C, 10.0 days), drops to (10 °C, 7.0 days), then to (15 °C, 5.0 days), then to (20 °C, 3.5 days), and levels off at (25 °C, 2.0 days), staying flat at 2.0 days up to 30 °C. 3. Grape juice (dotted line): starts at (5 °C, 7.0 days), drops slightly to (10 °C, 6.5 days), remains flat at 6.5 days until 15 °C, then drops to (20 °C, 5.0 days), then to (25 °C, 4.0 days), and finally down to (30 °C, 3.0 days). A key shows: Solid line = Apple juice, Dashed line = Orange juice, Dotted line = Grape juice.

a.

Which type of juice remains fresh the longest at 10 ∘C10\ ^\circ\text{C}10 ∘C?

[1]
b.

Describe the effect of temperature on the time taken for orange juice to reach pH 3.5. Use data from the graph in your answer.

[2]
c.

The time taken for apple juice to reach pH 3.5 at 15 ∘C15\ ^\circ\text{C}15 ∘C is less than at 5 ∘C5\ ^\circ\text{C}5 ∘C. Suggest one reason why.

[2]

7.2 Organisation of an ecosystem Questions

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