Topic: Scientific MethodAim: Explain how a controlled

experiment is performed.

Do Now: Why did I give you this sentence yesterday?

People hate elephants on couches.

HW: Study for your lab safety quiz!

True or False?

1.Gloves are not needed when doing dissections.

2.Students may eat or drink during certain experiments , but not during others.

3.Microscopes must be carries with 2 hands and held clode to the body.

4. Chemicals that are safe by themselves will not be hazardous when mixed together.

5. It is not necessary to wash your hands after every laboratory experiment.

6. All sharp and pointed objects should be handles with extreme care.

7. All materials can be safely rinsed down the sink.

8. When entering a classroom, plants, animals and equipment are never to be handled without directions from the teacher.

Review:

1. The first step in the scientific method is

a. to state the problem

b. Experimentation

c. to state the hypothesis

d. observation

2. Information gained from experimentation and observation is known as

a. theory

b. data

c. laws

d. hypothesis

3. An educated guess to the problem of an experiment is known as a

a. variableb. theoryc. hypothesisd. law

4. When performing an experiment, you are testing the

a. problemb. hypothesisc. datad. conclusion

5. Your senses can be used to make a(n)

a. observation b. conclusion c. hypothesis d. problem

Does fertilizer X help plant growth?

• ONE factor that is different

• Changes in each set up

Variable

• 2 groups:1.Experimental

group: contains the VARIABLE

2.Control group: DOES NOT contain the variable

Parts of a controlled experiment

Control Group Experimental Group

•Everything bw groups must be exactly the same except for the variable!!!

1. Independent Variable: the 1 factor that’s different between experimental and control groups

2 types of variables

Independent variable = ?

SUNLIGHT

2. Dependent Variable = what is MEASURED

•data or results obtained

HEIGHT

Height = 21 cmHeight = 12 cm

•Repeat experiment

•Use a larger sample size

•Use only one variable

To make results of an experiment more reliable or valid

Experiment

1.What is the independent variable?

2.What is the dependent variable?

3.Explain the difference between the control group and experimental groups in this experiment.

Let’s summarize…

1. Explain the difference between the control and experimental groups.

2. Explain the difference between the independent and dependent variables.

3. How can the results of an experiment be more accurate?

Review:To investigate how temperature affects seed

germination, a student placed 10 radish seeds of the same variety on moist paper in each of 3 petri dishes and placed the dishes in the following environments:

Dish # 1: Refrigerator, 5ºC

Dish # 2: Room Temperature, 20ºC

Dish # 3: Incubator, 37ºC

1. Which factor is the variable in this investigation?

a. temperature b. kind of seeds

c. moisture d. number of seeds

To investigate how temperature affects seed germination, a student placed 10 radish seeds of the same variety on moist paper in each of 3 petri dishes and placed the dishes in the following environments:

Dish # 1: Refrigerator, 5ºC

Dish # 2: Room Temperature, 20ºC

Dish # 3: Incubator, 37ºC

2. The control group is

a. Dish #1 b. Dish #2 c. Dish #3

3. The dependent variable is the

a. temperature b. how many days till germination

c. The # of seeds d. the amount of water

4. What is the factor in an experiment that remains constant?

a. control

b. variable

c. theory

d. hypothesis

5. Which statement is true about the experimental group (s) in an experiment?

a. It does not contain the independent variable.

b. It contains 2 variables.

c. It contains the independent variable.

d. It is exactly the same as the control group.

6. The results of one experiment carried out by a research team would be considered valid if

a. the experiment had no control setup

b. all the members of the research team came to the same conclusion

c. the experiment had more than one variable

d. the experiment was repeated and the same results were obtained each time

An investigation was done with an electromagnetic system made from a battery and wire wrapped around a nail. Different sizes of nails were

used. The number of paper clips the electromagnet could pick up was

measured.

Independent variable:

•Sizes of nails•These were changed by the scientist

Dependent variable:

•Number of paper clips picked up

The higher the temperature of

water, the faster an egg will boil.

•Independent variable?•temperature of water•Dependent variable?•time to cook an egg

Beta-carotene supplements have been thought to protect against cancer. A study was conducted with 39,000 women aged 45 and up. Group A received a beta-carotene supplement. Group B received a placebo. Their health was studied over their lifetime. Cancer rates for women taking the beta-carotene supplement did not really differ from the cancer rates of those women taking the placebo.

Identify the independent variable, dependent variable, control group, and experimental group.

What is the independent variable?Substance ZWhat is the dependent variable? height

Ex # 2: To investigate the effect of a substance on plant growth, 2 bean plants of the same species were grown under identical conditions with Substance Z added to the soil of one of the plants. At the end of 2 weeks, the plant grown with Substance Z was 12.5 cm tall. The plant grown without Substance Z was 12.2cm tall. The researcher concluded that the presence of Substance Z causes the plants to grow taller.

Which setup is the control?Plant without Substance Z

What is the independent variable?What is the dependent variable?Which setup is the experimental group?

Ex #3: A student placed 5 geranium plants of equal size in 5 environmental chambers. Growing conditions were the same for each plant except for the amount of water each received. At the end of 20 days, the width of the leaves was measured.

5. An investigation was designed to determine the effect of ultraviolet light on mold spore growth. Two groups of mold spores were grown under identical conditions, except one group was exposed only to ultraviolet light, while the other group was grown in total darkness. In this investigation, the group of mold spores grown without receiving any ultraviolet light is known as the

a. experimental variableb. hypothesisc. controld. limiting factor