Scientific Method

1. Scientific Method Chapter 1 - Section 2

2. “Mystery Worms” A teacher collected some beetles from a rotting log and placed them in a container of dry oatmeal in her classroom. She kept the box covered with a light cloth so that the beetles could not escape. She also asked one of her students to add potato and apple pieces once a week to provide food and moisture for the beetles. After several weeks, the student reported that there were some strange-looking, wormlike organisms in the container.

3. 1. Formulate a hypothesis that might explain the presence of the “worms” in the container. • 2. How could you test your hypothesis? • 3. Identify the variables in your proposed experiment. Identify the control in your proposed experiment

4. Step One: Ask a Question • Based on: • 1. observations (gathering info) • 2. inferences (prior knowledge) • … of events or processes of the natural world • Example – Where do maggots come from?

5. Step Two: Form a Hypothesis • The statement that is your answer to your question. • It is a statement – not a question • Remember – It must be able to be tested !! • Example – Maggots come from flies. or Maggots appear through Spontaneous Generation. What is That?????

6. Spontaneous Generation • The idea that life can arise or appear from nonliving matter. • This is the way scientists believed how maggots “appeared” on spoiled food many centuries ago. • It was rejected by the experiments of many scientists that proved that all living things come from existing living things.

7. Step Three: Setting up a Controlled Experiment • In science, testing a hypothesis usually involves designing an experiment. • Factors in an experiment that can change are called VARIABLES. • Examples of Variables include: - equipment used - temperature - type of materials - light - amount of materials - time

8. Whenever possible, a hypothesis should be tested by an experiment in which only ONE VARIABLE is CHANGEDAT A TIME. • ALL OTHER VARIABLES should be kept UNCHANGED or CONTROLLED • This type of experiment is called a CONTROLLED EXPERIMENT

9. Types of Variables 1. Controlled Variables 2. Manipulated Variable 3. Responding Variable

10. ControlledVariables -the factors that are controlled or unchanged during the experiment (type of equipment, material used, location, time, temperature)

11. Manipulated Variable: • the factor that is deliberately changed during the experiment • Only ONE Factor is CHANGE

12. Responding Variable - the variable that is observed and that changes in response to the manipulated variable

13. Step Four:Record & Analyze Results • Scientists keep written records of their observations and data of experiments. • Use drawings, tables, and graphs to organize the data. • Use computer programs to store and analyze data.

14. Step Five:Draw a Conclusion • Scientists use the data to evaluate the hypothesis and draw a valid conclusion. • They use the evidence to determine whether the hypothesis is supported or rejected.

15. Question – Where do maggots come from? OBSERVATIONS: Flies land on meat that is left uncovered. Later, maggots appear on the meat. HYPOTHESIS: Flies produce maggots. Uncovered jars Covered jars PROCEDURE Controlled Variables: jars, type of meat, location, temperature, time Several days pass Manipulated Variables: gauze covering that keeps flies away from meat Responding Variable: whether maggots appear Maggots appear No maggots appear CONCLUSION: Maggots form only when flies come in contact with meat. Spontaneous generation of maggots did not occur.

16. Designing an Experiment Section 1-2 State the Problem Analyze Results Form a Hypothesis Draw a Conclusion Set Up a Controlled Experiment Publish Results Record Results

17. When Experiments Are Not Possible

18. As scientists look for explanations for specific observations, they assume that the patterns in nature are consistent. • This means that if an experiment proves an hypothesis it SHOULD be CONSISTENT for all other experiments performed the same way.