11 Scientific Experiments Follow Rules An experimenter changes one factor and observes or measures what happens.
12 The Control VariableThe experimenter makes a special effort to keep other factors constant so that they will not effect the outcome.Those factors are called control variables.
13 What is the Purpose of a Control? Controls are NOT being testedControls are used for COMPARISON
14 Other VariablesThe factor that is changed is known as the independent variable.The factor that is measured or observed is called the dependent variable.
15 Example of Controls & Variables For example, suppose you want to figure out the fastest route to walk home from school.You will try several different routes and time how long it takes you to get home by each one.Since you are only interested in finding a route that is fastest for you, you will do the walking yourself.
16 What are the Variables in Your Experiment? Varying the route is the independent variableThe time it takes is the dependent variableKeeping the same walker throughout makes the walker a control variable.
17 One more thing… it is best to make several trials with each independent variable.
19 Remember: To be a Valid Experiment: Two groups are required --- the control & experimental groupsThere should be only one variable
20 Data Results of the experiment May be quantitative (numbers) or qualitative
21 DataMust be organizedCan be organized into charts, tables, or graphs
22 ConclusionThe answer to the hypothesis based on the data obtained from the experiment
23 In order to verify the results, experiments must be retested.
24 Measurement Scientific investigations usually require measurements. All scientists use a consistent measurement system; SI (System International) or the metric system
25 Units of Metric Measurement Length: linear distancesMillimeter (mm); centimeter (cm); meter (m); kilometer (km)Mass: the measure of how much matter something hasMatter is defined as anything that takes up space and has massGram (g); kilogram (kg); metric ton
26 Units of Metric Measurement Volume and area:Area is the amount of surface within a set of boundaries; square units of length (m2)Volume is the amount of space occupied by an object; depends on the type of objectSolids are measured in cubic units (m3)Liquids are measured in milliliters or liters; mL or L.
27 Units of Metric Measurement Density: the measure of the amount of matter that takes up a certain spaceMass divided by volumeGrams per cubic centimeter (g/cm3)Time: measured in seconds or minutesTemperature: usually in CelsiusKelvin is the official SI unit for temperatureAbsolute zero is -273oC or 0K
29 Solving a Problem 1)Identify a Problem 2) State Observations about the problem3) Form a Hypothesis about the problem (if…then…)4) Design an Experiment to test the hypothesis5) Collect Data6) Form a Conclusion7) Retest
30 Learning TargetsCompare and contrast independent and dependent variables.Discuss the parts of the scientific methodDiscuss the units of the metric system