1. Planning Your Own Experiment

2. Let’s Review. What are the steps of the scientific method? 1.Observation 2.Question 3.Hypothesis 4.Materials 5.Procedure 6.Data 7.Analysis 8.Conclusion To write a good procedure, you need to know the three kinds of variables: 1.Independent 2.Dependent 3.Control

3. Identify the variables of this experiment ( experiment stories are from http://www.cposcience.com/home/Portals/2/Media/post_sale_content/PES/PES_Chap_02/SkillandPracticeSheets/2_2_Identifying_Control_and_Exp_Vari ables.pdf.) http://www.cposcience.com/home/Portals/2/Media/post_sale_content/PES/PES_Chap_02/SkillandPracticeSheets/2_2_Identifying_Control_and_Exp_Vari ables.pdf “Alex is studying the effect of sunlight on plant growth. His hypothesis is that plants that are exposed to sunlight will grow better than plants that are not exposed to sunlight. In order to test his hypothesis, he follows the following procedures. He obtains two of the same type of plant, puts them in identical pots with potting soil from the same bag. Then he puts one plant in the sunlight and the other in a dark room. He waters the plants with 200 mL of water every other day for two weeks.” At the end of his experiment he measures and records the height of each plant.

4. Question: What is the effect of sunlight on plant growth Hypothesis: Plants exposed to sunlight grow better Independent Variable: Amount of Sunlight Control Variables: Type of plant, pot, soil, amount of water, schedule for watering the plants Dependent Variable: Height of plant

5. Now plan your own experiment #1 “John notices that his mom waters the plants in their house every other day. He asks, ‘Will plants grow if they are not watered regularly?’” Question: Hypothesis: Independent Variable: Control Variables: Dependent Variable:

6. Sample answer “John notices that his mom waters the plants in their house every other day. He asks, “Will plants grow if they are not watered regularly?” He hypothesizes that plants that are not watered regularly will not grow as large as plants that are watered regularly. In order to test his hypothesis, he conducts the following experiment. a. Obtain two healthy plants of the same variety and size. b. Plant each plant in the same type of pot and the same brand of potting mix. c. Place both plants in the same window of the house. d. Water one of the plants every other day with 250 mL of water. e. Water the other plant once a week with 250 mL of water. f. Measure the height of the plants once a day for one month.” Question: Will plants grow if not watered regularly? Hypothesis: No Independent Variable: Schedule to water Control Variables: amount of water, type of plant, size of plant, pot, potting mix, location Dependent Variable: Height of plants

7. Now plan your own experiment #2 “Mike’s dad always buys bread with preservatives because he says it lasts longer. Mike asks, ‘Will bread with preservatives stay fresh longer than bread without preservatives?’” Question: Hypothesis: Independent Variable: Control Variables: Dependent Variable:

8. Sample answer “Mike’s dad always buys bread with preservatives because he says it lasts longer. Mike asks, “Will bread with preservatives stay fresh longer than bread without preservatives?” He hypothesizes that bread with preservatives will not grow mold as quickly as bread without preservatives. In order to test his hypothesis, he conducts the following experiment. a. Obtain one slice of bread containing preservatives and one slice of bread without any preservatives. b. Dampen two paper towels. Fold the paper towels so that they will lay flat inside a zipper-top bag. c. Lay each paper towel inside a separate zipper-top bag. d. Place one slice of bread in each bag and seal the bags. e. Place bags with bread and paper towels in a dark environment for one week. f. Record mold growth once a day for one week.” Question: Will bread with preservatives last longer Hypothesis: yes Independent Variable: preservatives in the bread Control Variables: number of slices, moist paper towels, bags, location Dependent Variable: amount of mold growth