Brainlag PlusRates from gradients and leaf discs, temperature and carbon dioxide data, and predicting rates and distances with the inverse square law (Higher).
Rates from graphs and timings
On a graph of oxygen volume against time, the gradient is the rate: a steeper line means more oxygen each minute.
- Lamp at 10 cm: 24 cm³ in 10 minutes, rate = 24 ÷ 10 = 2.4 cm³/min
- Lamp at 30 cm: 8 cm³ in 10 minutes, rate = 8 ÷ 10 = 0.8 cm³/min
- (2.4 − 0.8) ÷ 0.8 × 100 = 200% increase
Another method times how long leaf discs take to float, as oxygen collects in them. A longer time means a slower rate, so a rate can be worked out as 1000 ÷ mean time. Leave out any anomalous result before you take the mean.
The rest of this lesson and its 11 practice questions are in Plus.
Screen 1 of 4, free to read.
- 11 exam-style questions, marked as you go, each with a worked solution
- Anything you get wrong is saved to your flashcards