The Scientific Method• there’s no single method to

answering questions or solving problems. • However, there is one characteristic

of scientific problem solving: the logical & organized approach that’s taken: The Scientific Method

1. Define the problem2. Form a hypothesis 3. Design an *experiment to

test the hypothesis4. Conclusion5. Theory

1. State the problem or objective – This is a statement of the problem or what you would like to know about something

2. Hypothesis – A hypothesis is a statement that predicts what you think will happen when you perform an experiment based on the information that you have gathered.

3. Controlled Experiment – isolates one variable and tests its effects on another.

• A variable is any factor or condition present in the experiment.

Experimental group – the group in which the variable is tested.

a) Independent variable – the variable being tested (cause) It’s the variable that is isolated and changed in a controlled way monitoring to see if it causes an effect on a second variable- the dependent variable

b) Dependent variable – the variable being observed for change (effect)

c) Constants - all other variables present in the experiment that remain the same throughout the experiment. Eg: same plants, soil, temp.

• Control group – group with the independent variable absent.

• This group is usually the "normal" conditions group used as a baseline to calculate the actual effect of the independent variable.

Sample size: of both should be = & representative & be large enough to have reliable data. The larger the size the more reliable the data

4. Collect Data – The observations gathered are recorded. Must be measurable. (tables and drawings)

5. Conclusion – The conclusion is a statement, based on the data, stating if the hypothesis was proven correct or not and why.

6. Theory – based upon results of experiment. They usually hold true ‘till new evidence proves otherwise.

HW: Summary of notes & questions

1. What is the scientific method?2. What are the steps of the scientific

method?3. What is the purpose of an experiment?4. Define: • Control• Independent & dependent variable

Scientific Method Wrkshts Answers

The Simpsons and the Scientific Method The Homer Scenario

• Homer notices that his shower is covered in a strange green slime. His friend Barney tells him that coconut juice will get rid of the green slime. Homer decides to check this out by spraying half of the shower with coconut juice. He sprays the other half of the shower with water. After 3 days of "treatment" there is no change in the appearance of the green slime on either side of the shower.

1. What was the initial observation? • Green slime was growing in the shower 2. Identify the Control Group • Shower half that was treated with water 3. Identify the Independent Variable • Liquid/solution used 4. Identify the Dependent Variable • Growth of the slime 5. What should Homer's conclusion be? • 3 days of treatment with coconut juice did not remove

the green slime

The Bart Scenario • Bart believes that mice exposed to microwaves

will become extra strong (maybe he's been reading too much Radioactive Man). He decides to perform this experiment by placing 10 mice in a microwave for 10 seconds. He compared these 10 mice to another 10 mice that had not been exposed. His test consisted of a heavy block of wood that blocked the mouse food. He found that 8 out of 10 of the microwaved mice were able to push the block away. 7 out of 10 of the non-microwaved mice were able to do the same.

6. Identify the Control Group • 10 mice not placed in the microwave 7. Identify the Independent Variable • Use of microwaves or not (exposure to

microwaves) 8. Identify the Dependent Variable • Number of mice that moved the block of wood 9. What should Bart's conclusion be? • Microwaves do not give mice extra strength 10. How could Bart's experiment be improved? • Use another source of energy, repeat the process,

try more mice

The Krusty Scenario • Krusty was told that a certain itching powder

was the newest best thing on the market. It even claims to cause 50% longer lasting itches! Interested in this product, he buys the itching powder and compares it to his usual product. One test subject (A) is sprinkled with the original itching powder, and another test subject (B) was sprinkled with the Experimental itching powder. Subject A reported having itches for 30 minutes. Subject B reported to have itches for 45 minutes.

11. Identify the Control Group • Test subject A 12. Identify the Independent Variable • Type of itching powder 13. Identify the Dependent Variable • Length of time with itches 14. Explain whether the data supports the

advertisements claims about its product. • The data supports the claim, but only 2 tests

subjects is not sufficient.

The Lisa Scenario • Lisa is working on a science project. Her task is

to answer the question: "Does Rogooti (which is a commercial hair product) affect the speed of hair growth"? Her family is willing to volunteer for the experiment. Describe how Lisa would perform this experiment.

15. Identify the control group, the independent, dependent variables in your description.

15. Identify the control group, the independent, dependent variables in your description.

• Control: regular hair shampoo• Rogooti• Speed of hair growth Have ½ of her family & friends use regular

shampoo & the other ½ the Rogooti; measure in cm, the rate of hair growth each week for a month. See which groups hair grew the fastest.

Scientific Method In ActionThe Strange Case of BeriBeri

In 1887 a strange nerve disease attacked the people in the Dutch East Indies. The disease was beriberi. Symptoms of the disease included weakness and loss of appetite, victims often died of heart failure. Scientists thought the disease might be caused by bacteria. They injected chickens with bacteria from the blood of patients with beriberi. The injected chickens became sick. However, so did a group of chickens that were not injected with bacteria.

One of the scientists, Dr. Eijkman, noticed something. Before the experiment, all the chickens had eaten whole-grain rice, but during the experiment, the chickens were fed polished rice. Dr. Eijkman researched this interesting case. he found that polished rice lacked thiamine, a vitamin necessary for good health.

1. State the Problem What causes Beriberi? 2. What was the hypothesis? If the chickens are injected w/a bacteria, then they will

develop beriberi. 3. How was the hypothesis tested? They injected chickens with bacteria from the blood of

patients with beriberi. The injected chickens became sick4. Should the hypothesis be supported or rejected based on the

experiment? Rejected5. What should be the new hypothesis? If the chickens are feed polished rice, then they will develop

beriberi.

How Penicillin Was Discovered ?

In 1928, Sir Alexander Fleming was studying Staphylococcus bacteria growing in culture dishes. He noticed that a mold called Penicillium was also growing in some of the dishes. A clear area existed around the mold because all the bacteria that had grown in this area had died. In the culture dishes without the mold, no clear areas were present.

Fleming hypothesized that the mold must be producing a chemical that killed the bacteria. He decided to isolate this substance and test it to see if it would kill bacteria. Fleming transferred the mold to a nutrient broth solution. This solution contained all the materials the mold needed to grow. After the mold grew, he removed it from the nutrient broth. Fleming then added the nutrient broth in which the mold had grown to a culture of bacteria. He observed that the bacteria died.

6. Identify the problem. What is killing the bacteria?

7. What was Fleming's hypothesis? Mold must be producing a chemical that killed the bacteria.

8. How was the hypothesis tested?Fleming transferred the mold to a nutrient broth solution. This solution contained all the materials the mold needed to grow. After the mold grew, he removed it from the nutrient broth. Fleming then added the nutrient broth in which the mold had grown to a culture of bacteria. He observed that the bacteria died.

9. Should the hypothesis be supported or rejected based on the experiment?

Yes10. This experiment lead to the development of

what major medical advancement? Antibiotics