Rate of decay calculationsSpec 9.19B
You can measure decay by recording the mass of the biological material at intervals. The rate of decay is the change in mass over time.
rate of decay = change in mass ÷ time
percentage loss in mass = (change in mass ÷ original mass) × 100
Rate of decay
A sample of leaves had a mass of 12.0 g. After 6 days the mass was 7.2 g. Calculate the mean rate of decay in g per day and the percentage loss in mass.
- Change in mass = 12.0 − 7.2 = 4.8 g
- Rate = 4.8 ÷ 6 = 0.8 g per day
- Percentage loss = 4.8 ÷ 12.0 × 100 = 40 %
Answer: 0.8 g per day; 40 % loss
Quick check
Name two indicator species for clean water.
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Freshwater shrimps and stonefly nymphs.
What does blackspot fungus on roses indicate?
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Cleaner air, because it is sensitive to sulfur dioxide.
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Low temperature slows the enzymes of the decomposers.
Give the conditions for fast composting.
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Warm, moist and well supplied with oxygen.
State the equation for the rate of decay.
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Change in mass ÷ time.