S4.1.7 For the adult
Testing photosynthesis
How can you measure how fast a plant makes oxygen?
What this chapter teaches
The bubbles from a water plant in light are oxygen from photosynthesis. Counting them in a minute gives a rate. A fair test changes only the lamp distance, keeps the plant, water, time and heat the same, and takes a mean of repeated counts.
Three questions to ask
There is no one right wording. Listen for the idea.
- What do you change, what do you measure, and what do you keep the same?
- Why does the lamp need a beaker of water in front of it?
- What would you do about one count that is far from the rest?
After the chapter, the learner can
- Count oxygen bubbles from a water plant at different distances from a lamp
- Plan a fair test of how light changes the bubble rate
What they copy into their notebook
Count the bubbles per minute at several lamp distances. Change only the distance. Keep the plant, water, time and heat the same. Count three times and take the mean. Closer lamp, more light, more bubbles.