Bellringer Define these words: (use Ch 1 of your book) Define these words: (use Ch 1 of your book) Science Science Scientific methods Scientific methods Hypothesis Hypothesis Controlled experiment Controlled experiment Variable Variable

A Controlled Experiment Part of the scientific method

Review-Scientific Method Problem/ Question Problem/ Question Observations/Research Observations/Research Hypothesis Hypothesis Experiment Experiment Data/Results Data/Results Conclusion Conclusion Communicate Results Communicate Results

Variables A controlled experiment tests only one variable and all other factors remain the same. A controlled experiment tests only one variable and all other factors remain the same. Variable: A factor that can change. A variable can change other factors when it changes. Variable: A factor that can change. A variable can change other factors when it changes. Examples of variables: -Temperature-Light - Open vs. Closed container -Location-Time-Elevation-Pressure

The independent variable is the variable that is purposely changed. It is the manipulated variable. The dependent variable changes in response to the independent variable. It is the responding variable. Variables Variables are things that change.

Independent vs. Dependent Variables The dependent variable is a factor that changes because the independent variable changes. However the independent variable is not changed by the dependent variable. The dependent variable is a factor that changes because the independent variable changes. However the independent variable is not changed by the dependent variable. Example: Elevation and Boiling temperature of water. The boiling temperature of water changes because of changes in elevation. Changes in the boiling temperature of water do not change elevation. Example: Elevation and Boiling temperature of water. The boiling temperature of water changes because of changes in elevation. Changes in the boiling temperature of water do not change elevation.

Constants or Controlled Variables in an Experiment What are constants in an experiment? Factors that are kept the same and not allowed to change. It is important to control all but one variable at a time to be able to interpret data

Control -A variable or factor that does not change in the experiment. It remains constant. In a Controlled experiment only one variable is allowed to change at a time. Everything else remains constant.

Experimental Error Bias (what you expect to happen prevents you from observing what actually happens) Bias (what you expect to happen prevents you from observing what actually happens) Testing more than one independent variable. Testing more than one independent variable. Not having a control group. Not having a control group. Not having constants. Not having constants. Not using a large enough test group. Not using a large enough test group. Not repeating the experiment enough times. Not repeating the experiment enough times.

OBSERVATIONS: Flies land on meat that is left uncovered. Maggots appear on the meat. HYPOTHESIS: Flies produce maggots. VARIABLES Controlled Variables: jars, type of meat, location, temperature, time Independent Variables: gauze (keeps flies away from meat) Uncovered jars Covered jars After several days Maggots appear No maggots appear Dependent Variable: whether maggots appear CONCLUSION: Maggots form only when flies come in contact with meat. Spontaneous generation of maggots did not occur. Francisco Redi & Spontaneous Generation

Replicates In an experiment multiple copies of the experiment are done at the same time. In an experiment multiple copies of the experiment are done at the same time. This is to ensure that the results are accurate (true) and not due to a mistake, error or chance event. This is to ensure that the results are accurate (true) and not due to a mistake, error or chance event.

Treatments Set of variables in the experiment that are the same in each group of replicates. Set of variables in the experiment that are the same in each group of replicates. 2 Treatments 2 Treatments CoveredUncovered

Problem Problem Which pinto beans will grow better, those in fresh water or salt water?

Review Review What is a controlled experiment? An experiment with one group of test subjects being exposed to the variable, and one that is not treated with the _________ being tested! variable What is the variable being tested in the pinto bean experiment? Salt (How it EFFECTS the pinto bean growth)

Controlled Experiment Experimental GroupControl Group In the pinto bean experiment, which is the control group and which is the experimental group? What are the groups in a controlled experiment? -Gets NORMALTreatment (No Variable). -Used for comparison Gets the VARIABLE you are testing. Control Group: Experimental Group: Fresh water beans Salt Water Beans

1. Independent (manipulated)–is what the scientist controls or changes or it affects something. (SALT Affects Bean Growth) 2. Dependent (responding)–is the variable that is observed and that is affected by the independent variable. (BEAN GROWTH) Controlled Experiment Variables Variables: factors that can change What are the two types of variables?

Constants: are exactly the same for both the control and experimental groups. Both groups should be treated exactly the same except for the variable being tested. What are the constants in the pinto bean experiment? Experiment (Controlled) Constants Beaker Size Amount of Water Brand of Pinto Beans

Exit Assignment Identify the variables in this experiment: Identify the variables in this experiment: Can tomato plants grow without being exposed to sunlight? Can tomato plants grow without being exposed to sunlight? What is the independent variable? Dependent variable? Constants? What is the independent variable? Dependent variable? Constants? How would you set up the experiment to test this question? How would you set up the experiment to test this question?