The Nature of Science
Materials Needed
clear plastic cup
plastic wrap
paper towel, water
package of radish seeds
metric ruler
microwave oven
Step 1: Questions
• What is the effect of increasing exposure times of microwave radiation on radish seed germination?
• What is the effect of increasing exposure times of microwave radiation on radish seed sprout length?
Consider the questions above.
1) Write a hypothesis (prediction) for each question, in the below space. Make sure they are clear and testable! When writing a hypothesis use the If (statement about observations)...then (prediction of results of experiment)... format.
For example, If I drop a pencil, then it will fall.
Prediction 1
Prediction 2
Step 2: Testing your hypothesis (The Experiment)
• Prepare six plastic germination chambers by folding the paper towel into the bottom of a plastic cup and moisten the paper towel in each cup.
• Separate the radish seeds in the package into 6 groups of at least ten intact seeds in each group. Place each group of seeds into the microwave oven for a different amount of time. Use times of 0 sec, 10 sec, 20 sec 40 sec, 80 sec and 120 sec.
• Place each group in a separate cup and write the length of time the seeds were exposed to microwave radiation on the plastic cup. Also write down the date of the beginning of the experiment.
• Cover the seeds and the moistened paper towel to keep in the moisture during the next 6 days. You may need to add a few drops of water if the towel gets dry during the experiment.
• Store the plastic cups where they will not be disturbed, but in the light.
Answer the following questions (in the drop box) for this experimental setting. This web site may help.
https://chemistry.about.com/od/chemistryterminology/a/What-Is-The-Difference-Between-Independent-And-Dependent-Variables.htm
2) What is the independent variable?
3) What is the dependent variable?
4) Which of the groups of seeds would be the control group for this experiment?
RESULTS:
• Observe the radish seeds in your plastic dish for a "sprout" or leaflets coming out of the seed. Note: there may also be fine, white hair like rootlets-ignore those.
• After a week COUNT the number of seeds that you can see the "sprout" coming out of the seed--even if the sprout is very small. Don't count them if the outside coat of the seed has broken open but there is no "sprout.
• RECORD the number of seeds germinated for each group. CALCULATE the average percent of seeds that germinated by the sixth day for each exposure time.
• COUNT the number of the sprouts that germinated for each sprouted seed for each group on the sixth day. CALCULATE average germination percentage for each time exposure. You can do this by the following formula:
% Germination = Number of sprouts/Number of seeds tested x 100
5) PRODUCE a table with the percentage data of the germination rate for each group.
• MEASURE the length of the sprouts, in millimeters (mm), for each sprouted seed for each group after the 2nd week CALCULATE average sprout length for each time exposure. Make sure you identify the mm marks on the ruler- there are 25 mm in an inch and an mm is about the width of a period (.)
6) PRODUCE a table with the average sprout length for each group.
Conclusion:
7) Using your graphed data, discuss your conclusions concerning the effect of microwave exposure on germination rates and sprout lengths. Did the data support both of your hypotheses? If not, discuss why not!