Bellringer Define these words: (use Ch 1 of your book) Science Scientific methods Hypothesis Controlled experiment Variable A Controlled Experiment Part of the scientific method Review-Scientific Method Problem/ Question Observations/Research Hypothesis Experiment Data/Results Conclusion Communicate Results Variables 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. Examples of variables: -Temperature -Light - Open vs. Closed container -Location -Time -Elevation -Pressure Variables Variables are things that change. 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. 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. 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) Testing more than one independent variable. Not having a control group. Not having constants. Not using a large enough test group. Not repeating the experiment enough times. Francisco Redi & Spontaneous Generation OBSERVATIONS: Flies land on meat that is left uncovered. Maggots appear on the meat. HYPOTHESIS: Flies produce maggots. VARIABLES Covered jars Uncovered jars Controlled Variables: jars, type of meat, location, temperature, time After several days Independent Variables: gauze (keeps flies away from meat) Dependent 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. Replicates 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. Treatments Set of variables in the experiment that are the same in each group of replicates. 2 Treatments Covered Uncovered Problem Which pinto beans will grow better, those in fresh water or salt water? Review What is a controlled experiment? • An experiment with one group of test subjects being exposed to the variable, and one that is not variable being tested! treated with the _________ What is the variable being tested in the pinto bean experiment? Salt (How it EFFECTS the pinto bean growth) Controlled Experiment What are the groups in a controlled experiment? Control Group Experimental Group -Gets NORMALTreatment (No Variable). -Used for comparison Gets the VARIABLE you are testing. In the pinto bean experiment, which is the control group and which is the experimental group? Control Group: Fresh water beans Experimental Group: Salt Water Beans Controlled Experiment Variables Variables: factors that can change What are the two types of variables? 1. 2. Independent (manipulated)–is what the scientist controls or changes or it affects something. (SALT Affects Bean Growth) Dependent (responding)–is the variable that is observed and that is affected by the independent variable. (BEAN GROWTH) Experiment (Controlled) Constants 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? • Beaker Size • Amount of Water • Brand of Pinto Beans Exit Assignment Identify the variables in this experiment: Can tomato plants grow without being exposed to sunlight? What is the independent variable? Dependent variable? Constants? How would you set up the experiment to test this question?