Standard Science Primary 6 Energy

A plant was kept in a sealed glass jar with adequate water and nutrients. Which of the following describes the change in the oxygen level inside the jar over a 24-hour period?

A Oxygen level decreases during the day and increases during the night.
B Oxygen level increases steadily for the entire 24 hours.
C Oxygen level increases during the day and decreases during the night.
D Oxygen level remains constant throughout the 24 hours.
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Worked Solution

Step 1: During the day, the rate of photosynthesis is higher than the rate of respiration, so oxygen is released. Step 2: At night, only respiration occurs, so oxygen is consumed. Step 3: Therefore, oxygen levels rise in the light and fall in the dark.

Correct answer: Oxygen level increases during the day and decreases during the night.

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