1. The Scientific Method

3. Objectives I will be able to:  Identify the different parts of the scientific method  Write a scientific procedure  Apply the use of the scientific method to common problems

4. Purpose of scientific method  Used to explain things we see

5. Step 1: Observe a problem  In the natural world

6. Observations/Identify a Problem  Example of an observation - many salamanders near a pond have curved, not straight, tails

7. Step 2: Hypothesis  A suggested solution to the problem.  Must be testable

8. Hypothesis  Example of a hypothesis - salamanders have curved tails due to a pollutant in the moist soil where they live.

9. Step 3: Experiment  A procedure to test the hypothesis.

10. Experiment  Variable – factor in the experiment that is being tested  A good or “valid” experiment will only have ONE variable  Why?

11. Experiment Independent variable – what I control Dependent variable – what is being measured; depends on changes in the independent variable

12. Experiment Example: test score and time spent studying Independent variable – time spent studying (I control) Dependent variable – test score (depends on time spent studying)

13. Experiment Control Group – the group which is NOT being tested Experimental Group – the group(s) being tested; receives different amounts of independent variable

14. Example Study Time vs. Test Score 5 kids do not study for a test 5 students study for 30 minutes Control Group – the group which is NOT being tested (5 kids that don’t study) Experimental Group – the group(s) being tested (5 students who study)

15. Example of Controls & Variables  For example, suppose you want to figure out the fastest route to walk home from school.  You will try several different routes and time how long it takes you to get home by each one.  Since you are only interested in finding a route that is fastest for you, you will do the walking yourself.

16. What are the Variables in Your Experiment?  Varying the route is the independent variable (I Control!)  The time it takes is the dependent variable  Keeping the same walker throughout makes the walker a control variable.

17. Step 4: Analyze Data What does your data show?

18. Step 5: Interpret Data & Draw Conclusion Does your data support your hypothesis?

19. Retest You can do the experiment many times to make sure the results are accurate.

20. Step 6: Share Results  Share results with other scientists  Include very specific procedure  Why?

21. I Do  You like to garden, and notice that some tomatoes are bigger than others and wonder why. You think that one group is bigger because it receives more sunlight than the others. You decide to split the tomatoes up into 2 groups. Everything between the tomatoes is the same, but one group gets no sunlight, and the other gets 6 hours of sunlight a day. You find that the group that gets more sunlight grows larger than the group that receives no sunlight.

22. I Do  Observation: some tomatoes are bigger than others  Hypothesis: tomatoes grow bigger when they receive more sunlight  Independent variable: amount of sunlight  Dependent variable: size of tomatoes  Control group: tomatoes with no sunlight  Experimental group: tomatoes with sunlight  Result: hypothesis supported!

23. We Do  You notice that your friend’s goldfish is much bigger than yours. You both feed it the exact same food in the same amount. You believe that his goldfish is bigger because it lives in a bigger tank. You buy 2 new goldfish, feed them the exact same thing in the same amount and put them in the same water. One is put in a small bowl. The other is put in a big bowl. The one in the big bowl grows to be twice as big.

24. We Do  Observation:  Hypothesis:  Independent variable:  Dependent variable:  Control group:  Experimental group:  Result:

25. We Do  Observation: One fish is bigger than the other  Hypothesis: Fish grow to be bigger if they live in bigger bowls  Independent variable: bowl size  Dependent variable: fish size  Control group: fish in small bowl  Experimental group: fish in big bowl  Result: hypothesis supported!

26. You Do In Pairs  I really like when my mom makes cheeseburgers, but I always feel sick afterwards. I believe the cheese is what makes me sick. My mom makes a new batch of burgers, 5 with cheese, and 5 without. I find that when I eat the regular hamburger, I don’t feel sick afterwards.

27. You Do In Pairs  Observation: I feel sick after eating cheeseburgers  Hypothesis: The cheese makes me sick  Independent variable: Cheese  Dependent variable: Sickness  Control group: Burgers without cheese  Experimental group: burgers with cheese  Result: hypothesis supported!