1. Scientific Method

2. Steps in the Scientific Method
Observation
Hypothesis
Experiment
Data Collection
Conclusion
Retest

3. Observations Gathered through your senses
A scientist notices something in their natural world

4. Observations
An example of an observation might be noticing that many salamanders near a pond have curved, not straight, tails

5. Problem Statements Defines topic of experiment
Gives reader idea of what experiment is about
NOT a yes/no question
Defines a relationship you want to study

6. Problem Statements For example:
How does size of parachute affect the time it takes for the weight to reach the ground?

7. Problem Statements
For each of the following topics, write two possible problem statements:
1. Designing a bridge
2. Properties to help a boat float
3. Plant growth (height, or # of blooms)

8. Problem Statements Possible answers:
1. How does the length of a bridge affect how much mass it can hold?
2. How does the surface area of the bottom of a boat affect the mass it can hold?
3. How does watering frequency affect plant height?

9. Hypothesis A suggested solution to the problem. Must be testable
Written as If…Then… Because…statements
Because = rationale for hypothesis
Predicts an outcome

10. Hypothesis
Example of Hypothesis: If the salamanders have curved tails, then it is due to a pollutant in the moist soil, because other populations of salamander do not have curved tails

11. Hypothesis
Write a hypothesis for each of the following problem statements:
1. How does the amount of light affect the height of a plant?
2. How does the surface area of the bottom of a boat affect the mass it can hold?
3. How does the length of a bridge affect the mass it can hold?

12. Hypothesis Possible answers:
1. If a plant gets more sunlight, then it will grow taller, because it can make more food through photosynthesis
2. If the surface area of the bottom of a boat is larger, then the boat can hold more mass, because the mass will be more evenly dispersed.

13. A procedure to test the hypothesis.
Experiment
A procedure to test the hypothesis.

14. Experiment
Procedure – A series of steps followed in a regular definite order.
Should be easy to follow
Should include detail
Should have step-by-step directions
Include exact measurements

15. Experiment Sample Procedure #1:
1. Number each battery so you can tell them apart.
2. Measure each battery's voltage by using the voltmeter.
3. Put the same battery into one of the devices and turn it on.
4. Let the device run for thirty minutes before measuring its voltage again. (Record the voltage in a table every time it is measured.)
5. Repeat #4 until the battery is at 0.9 volts or until the device stops.

16. Experiment Sample Procedure #2:
1. Put two identical bowls on the counter.
2. Take two ice cubes out of the freezer and place one in each bowl.
3. Break one of the ice cubes into smaller pieces that are no larger than 1/4 the size of the whole ice cube.
4. Time how long it takes for all the ice to melt.

17. Experiment Think, Pair, Share:
Which of the two procedures represents a good procedure? What makes it a good procedure?

18. Variable – factor in the experiment that is being tested

19. A good or “valid” experiment will only have ONE variable!

20. Scientific Experiments Follow Rules
An experimenter changes one factor and observes or measures what happens.

21. The Control Variable
The experimenter makes a special effort to keep other factors constant so that they will not affect the outcome.
Those factors are called control variables.

22. What is the Purpose of a Control?
Controls are NOT being tested
Controls are used for COMPARISON

23. Other Variables
The factor that is changed is known as the independent variable.
The factor that is measured or observed is called the dependent variable.

24. 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.

25. What are the Variables in Your Experiment?
Varying the route is the independent variable
The time it takes is the dependent variable
Keeping the same walker throughout makes the walker a control variable.

26. One more thing… it is best to make several trials with each independent variable.

27. Remember: To be a Valid Experiment
Two groups are required --- the control & experimental groups
There should be only one variable

28. Data Results of the experiment Measuring of dependent variables
May be quantitative (numbers) or qualitative

29. Data Collect during and after experiment Must be organized
Can be organized into charts, tables, or graphs

30. Conclusion
The answer to the hypothesis based on the data obtained from the experiment
Decide if hypothesis is supported or not

31. Conclusion
Cannot make conclusions until after experiment is repeated several times
Conclusions based on experimental data

32. In order to verify the results, experiments must be retested.

33. Peer Review Publish experiment and results in scientific journals
Other scientists read experiment and review procedure/results
If others try experiment and find hypothesis support many times, then the hypothesis may become a theory

34. Solving a Problem 1)Identify a Problem
2) State Observations about the problem
3) Form a Hypothesis about the problem (if…then…)
4) Design an Experiment to test the hypothesis
5) Collect Data
6) Form a Conclusion
7) Retest / Peer Review