Page 10 - 新思维科学学生用书9 样章

1.1 Photosynthesis

Think like a scientist

Investigating how light intensity affects the rate of photosynthesis

Like the previous experiment, this experiment uses a water plant. You are going
to change the amount of light that falls onto the plant and see how this affects the
number of bubbles it produces in one minute.

You will need:
• a test tube containing water, a piece of water plant, a lamp, a beaker in which
you can stand the test tube, a ruler for measuring the distance between the

lamp and the test tube, a timer.

Safety

It is very important to keep electrical wires, plugs and the
lamp away from the water.

Method
1 Set up your equipment. Place the lamp close to

the test tube. Leave the equipment like that for
about 5 minutes, to give the plant time to settle
down and start to photosynthesise.
While you are waiting, read the rest of these

instructions and then draw a results chart.
When you can see bubbles coming from the cut end of the plant stem, you can
start your experiment.
2 Measure the distance between the lamp and the test tube, and write it down in

your results chart.
3 Start the timer. Count how many bubbles the plant produces in one minute, and
write this down.
4 Repeat step 3 two more times.

5 Now move the lamp a little bit further away from the test tube. Measure the new
distance.
6 Repeat steps 3 and 4.
7 Repeat steps 5 and 6 for at least two more distances of the lamp, further from

the test tube.

9