1/20/11- Light Experiment

Elodea

First, we discussed the problems we had in the experiment yesterday to make sure that it didn't happen again today. The problems that we had were that the Elodea wasn't big enough and it floated, oxygen bubbles were counted even if they weren't coming from the stem, and the amount of sodium bicarbonate in each test tube was different in each group, which caused different results. Also, if you crushed the sodium bicarbonate on the table instead of a peice of paper, it lost mass because some was left on the table when it was swept into the test tube.

Next, we did the experiment. These were the steps in the light experiment;

1. Set up the experiment. Put .3g of crushed sodium bicarbonate and 20ml. of water into the test tube. Crush the end of the Elodea and place it in the test tube with the stem facing up. Plug in the lightbulb. After that, use tape to mark 10, 20, and 30 cm away from the light source. Place the test tube 10 cm away from the light.

2. Start the timer and count the oxygen bubbles coming from the crushed stem for 4 minutes. Record the results.

3. Repeat step 2 but at 20cm. away from the light. Record the results.

4. Repeat step 2 but at 30cm. away from the light. Record the results.

The results for the experiment were....

10cm- 1 oxygen bubble

20cm- 3 oxygen bubbles

30cm- 6 oxygen bubbles

M.K.B.