Observations often lead to questions ---> which lead to experiments to answer the questions.

Transcription

1 Introduction Science is ultimately based on observation (perceiving objects or events using one of the five senses). Observations often lead to questions ---> which lead to experiments to answer the questions. The Scientific Method involves a series of steps that are used to investigate a natural occurrence. The Steps of the Scientific Method 1. Problem/Question 2. Observation/Research 3. Formulate a Hypothesis 4. Experiment/ Test 5. Collect and Analyze Results 6. Conclusion 7. Communicate the Results 1. Problem/Question: Develop a question or problem that can be solved through experimentation. 2. Observation/Research: Make observations and research your topic of interest. 3. Formulate a Hypothesis: Predict a possible answer to the problem or question. Example: If soil temperatures rise, then plant growth will increase. Page 1 of 11

2 4. Experiment: Develop and follow a procedure. Include a detailed materials list. The outcome must be measurable (quantifiable). 5. Collect and Analyze Results: Modify the procedure if needed. Confirm the results by retesting. Include tables, graphs, and photographs. 6. Conclusion: Include a statement that accepts or rejects the hypothesis. Make recommendations for further study and possible improvements to the procedure. 7. Communicate the Results: Be prepared to present the project to an audience. Expect questions from the audience. Page 2 of 11

3 Terminology Before we go any further there are a few terms you will need to be familiar with: 1. HYPOTHESIS: The hypothesis is an educated guess about the relationship between the independent and dependent variables. 2. VARIABLES: Variable is a logical set of attributes such as measurable quantities, categories such as gender, numbers, or words. Variables vary can be high or low. 3. INDEPENDENT VARIABLES: or manipulated variable, is a factor that s intentionally varied by the experimenter. The researcher changes this variable, it is under their control. E.g. changing temperature, water quantities, etc. 4. DEPENDENT VARIABLES: or responding variable (responds to the independent variable dependent on the independent), is the factor that may change as a result of changes made in the independent variable. E.g. Plant growth, cell growth etc. Scientists cannot predict how high plants are going to grow, nor can they make them grow a certain height, they can only wait and see. 5. CONTROL GROUP: In a scientific experiment, the control is the group that serves as the standard of comparison. The control group may be a no treatment" or an experimenter selected group. The control group is exposed to the same conditions as the experimental group, except for the variable being tested. All experiments should have a control group. The control group is used to test whether the variable is working, and then measure the experiments against this standard. E.g. Controls are needed to eliminate alternate explanations of experimental results. For example, suppose a researcher feeds an experimental artificial sweetener to sixty laboratory rats and observes that ten of them subsequently die. The underlying cause of death could be the sweetener itself or something unrelated. Other variables, many of which may not be readily obvious, may interfere with the experimental design. For instance, perhaps the rats were simply not supplied with enough food or water, or the water was contaminated and undrinkable, or the rats were under some psychological or physiological stress, etc. Eliminating each of these possible explanations individually would be time-consuming and difficult. Instead, the researcher can use an experimental control, separating the rats into two groups: one group that receives the sweetener and one that does not. The two groups are kept in otherwise identical conditions, and both groups are observed in the same ways. Now, any difference in morbidity between the two groups can be ascribed to the sweetener itself and no other factor with much greater confidence. Page 3 of 11

4 6. CONSTANTS: The constants in an experiment are all the factors that the experimenter attempts to keep the same. 7. EXPERIMENTAL DESIGN DIAGRAM: This is used to design the experiment, and hypothesis being tested. Putting the Scientific Method into Practice Step 1: Problem/ Question John watches his grandmother bake bread. He asks his grandmother what makes the bread rise. She explains that yeast releases a gas as it feeds on sugar. John wonders if the amount of sugar used in the recipe will affect the size of the bread loaf. Step 2: Observation/ Research John researches the areas of baking and fermentation and tries to come up with a way to test his question. He keeps all of his information on this topic in a journal. John talks with his teacher and she gives him an Experimental Design Diagram to help him set up his investigation. Page 4 of 11

5 EXPERIMENTAL DESIGN DIAGRAM TITLE The effect of (independent variable) On (dependent variables) HYPOTHESIS If (planned change in independent variable) Then (predicted change in dependent variables) INDEPENDENT VARIABLE LEVELS OF INDEPENDENT VARIABLE & NUMBERS OF REPEATED TRIALS Level 1 (control) Level 2 Level 3 Level 4 Number of trials Number of trials Number of trials Number of trials DEPENDENT VARIABLES AND HOW WERE THEY MEASURED CONSTANTS Page 5 of 11

6 PROCEDURE DATA ORGAINZATION GRAPHIC REPRESENTATION Eleven parts of the Experimental Design Diagram 1. Title for experiment written as the effect of the independent variable on the dependent variable 2. Hypothesis in the form of an if-then statement 3. Independent variable 4. Different levels of the independent variable 5. Level of the independent variable that will serve as the control for the experiment 6. Number of repeated trials for each level of the independent variable 7. Dependent variables, including how they will be measured 8. Constants 9. Procedure: statements on how to carry out the experiment 10. Data organization is it a table, 11. Graphic representation can the data be graphed and what is the outcome of the graph? Step 3: Hypothesis After talking with his teacher and conducting further research, he comes up with a hypothesis. If more sugar is added, then the bread will rise higher. Step 4: Experiment/ Test John writes out his procedure for his experiment along with a materials list in his journal. He has both of these checked by his teacher where she checks for any safety concerns. Independent Variable: John is going to use 50g, 60g, 70g, 80g, and 90g of sugar in his experiment. Dependent Variable: The size of the loaf of bread Control Group: Because his grandmother always used 50g of sugar in her recipe, John is going to use that amount in his control group. Constants: Other ingredients to the bread recipe, oven used, rise time, brand of ingredients, cooking time, type of pan used, air temperature and humidity where the bread was rising, oven temperature, age of the yeast Page 6 of 11

7 Step 5: Collect and Analyze Data John comes up with a table he can use to record his data. John gets all his materials together and carries out his experiment. John examines his data and notices that his control worked the best in this experiment, but not significantly better than 100g of sugar. Step 6: Conclusion John finds that 70g of sugar produces the largest loaf. His hypothesis is accepted. Step 7: Communicating the Results John tells his grandmother about his findings and prepares to present his project in Science class. EXERCISE Page 7 of 11

8 1. Choosing Hypotheses 2. A scientist has 12 plants. All the plants were the same kind and about the same size. He put three plants on a window sill inside a room. He put another three plants in a closet without a light. He put another three more plants outside on the ground. He put his last three plants outside too, but covered them with paper bags that had holes punched in them for air. All the plants were given good soil and enough water. The plants on the window sill and the plants outside in the open grew well. The plants outside in the bags turned yellow and grew badly. The plants in the closet died. Which of the following is the best hypothesis based on the facts? a) Green plants turn yellow due to disease. b) Green plants don t live for very long. c) Green plants need light to grow. d) Green plants cannot grow inside e) Green plants grow well in closets. 3. Louis Pasteur, a famous scientist who lived over 100 years ago, made an important hypothesis about a certain germ called bacteria. He noticed that bacteria grew quickly in open jars of liquid, like chicken soup. Bacteria also grew in jars of soup that were sealed tightly so that no air could get in. However they didn t grow in soup that was sealed tightly in a jaw, then boiled and kept sealed after it cooled. When was Pasteur s correct hypothesis? a) Bacteria cannot grow in jars. b) Bacteria must have air to survive c) Bacteria only grow in chicken soup d) Bacteria can be killed by boiling. e) Bacteria can live in boiling liquids. 2. Errors in experiments Tell what is wrong with each of these experiments. Choose from this list: Not enough subjects Subjects were not similar. Conditions were not kept the same The experiment was not reproduced. 1. A gardener wanted to know if XYZ fertilizer would be good for this vegetable. He fertilized all his bean plants with XYZ but didn t put any fertilizer on his pepper plants. His beans didn t do well at all, but he got a good crop of peppers. He concluded that XYZ fertilizer was no good. 2. Alice Larsen wanted to see if a new premium gasoline would give her more kilometers to the liter. She filled her car with the new gas and went on a long trip. When she figured her mileage, she discovered that she has gone 40 Km farther on this tank of gas then she went on a tanks of regular gas when she was driving around town as usual. She decided to buy the premium gas for then on to get better mileage. Page 8 of 11

9 3. A molding machine in a factory was not working very well. About a third of the time, the plastic squirt guns that it was making come out with a flaw in the handle. The repair mechanic adjusted the stamping pressure. Then she ran one gun through. It came out just fine, so she figured she had solved the problem. 3. Comprehension The 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. a) State the Problem b) What was the hypothesis? c) How was the hypothesis tested? d) Should the hypothesis be supported or rejected based on the experiment? e) What should be the new hypothesis? 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 mould because all the bacteria that had grown in this area had died. In the culture dishes without the mould, no clear areas were present. Fleming hypothesized that the mould 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 mould to a nutrient broth solution. This solution contained all the materials the mould needed to grow. After the mould grew, he removed it from the nutrient broth. Fleming then added the nutrient broth in which the mould had grown to a culture of bacteria. He observed that the bacteria died. f) Identify the problem. g) What was Fleming's hypothesis? h) How was the hypothesis tested? i) Should the hypothesis be supported or rejected based on the experiment? Page 9 of 11

10 j) This experiment lead to the development of what major medical advancement? 4. Identify the Controls and Variables Smithers thinks that a special juice will increase the productivity of workers. He creates two groups of 50 workers each and assigns each group the same task (in this case, they're supposed to staple a set of papers). Group A is given the special juice to drink while they work. Group B is not given the special juice. After an hour, Smithers counts how many stacks of papers each group has made. Group A made 1,587 stacks, Group B made 2,113 stacks. 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. Identify the: 1. Control Group 2. Independent Variable 3. Dependent Variable 4. What should Smithers' conclusion be? 5. How could this experiment be improved? 6. What was the initial observation? Identify the- 7. Control Group 8. Independent Variable 9. Dependent Variable 10. What should Homer's conclusion be? Bart believes that mice exposed to radio waves will become extra strong (maybe he's been reading too much Radioactive Man). He decides to perform this experiment by placing 10 mice near a radio for 5 hours. 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 mice exposed to radio waves were able to push the block away. 7 out of 10 of the other mice were able to do the same. 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. Identify the- 11. Control Group 12. Independent Variable 13. Dependent Variable 14. What should Bart's conclusion be? 15. How could Bart's experiment be improved? Identify the- 16. Control Group 17. Independent Variable 18. Dependent Variable 19. Explain whether the data supports the advertisements claims about its product. - It does Page 10 of 11

11 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. 20. Describe how Lisa would perform this experiment. Identify the control group, and the independent and dependent variables in your description. Page 11 of 11