scientific method. steps in the scientific method observation observation hypothesis hypothesis...
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Steps in the Scientific Steps in the Scientific MethodMethod
ObservationObservation HypothesisHypothesis ExperimentExperiment Data CollectionData Collection ConclusionConclusion RetestRetest
ObservationsObservations
Gathered Gathered through your through your
sensessenses A scientist A scientist
notices notices something in something in their their natural natural
worldworld
ObservationsObservations
An An exampleexample of of an observationan observation
might be might be noticing that noticing that
many many salamanders salamanders near a pond near a pond
have curved, not have curved, not straight, tailsstraight, tails
HypothesisHypothesis
A suggested A suggested solution to the solution to the problem.problem.
Must be Must be testabletestable Sometimes Sometimes
written as written as If…If…Then…Then… statementsstatements
PredictsPredicts an an outcomeoutcome
HypothesisHypothesis
An An example of a example of a hypothesishypothesis might might be that the be that the salamanders salamanders have curved tails have curved tails due to a due to a pollutant in the pollutant in the moist soil where moist soil where they live. they live.
ExperimentExperiment
VariableVariable – – factor in the factor in the experiment experiment that is being that is being
testedtested
ExperimentExperiment
A good or A good or “valid” “valid”
experiment experiment will only will only
have have ONE ONE variable!variable!
Scientific Experiments Scientific Experiments Follow RulesFollow Rules
An experimenter changes one factor and observes or measures what happens.
The Control VariableThe Control Variable The experimenter makes a The experimenter makes a
special effort to keep special effort to keep other factors constantother factors constant so so that they will not effect that they will not effect the outcome.the outcome.
Those factors are called Those factors are called control variables.control variables.
What is the Purpose of What is the Purpose of a Control?a Control?
Controls are NOT being tested
Controls are used for COMPARISON
Other Variables The factor that is changed
is known as the independent variable.
The factor that is measured or observed is called the dependent variable.
Example of Controls & Example of Controls & VariablesVariables
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.
What are the Variables What are the Variables in Your Experiment?in Your Experiment?
Varying the route is the Varying the route is the independent variableindependent variable
The time it takes is the The time it takes is the dependent variabledependent variable
Keeping the same walker Keeping the same walker throughout makes the throughout makes the walker a walker a control variable.control variable.
Remember: To be a Remember: To be a Valid Experiment:Valid Experiment:
Two groups are required --- the control & experimental groups
There should be only one variable
Measurement Scientific investigations usually
require measurements. All scientists use a consistent
measurement system; SI (System International) or the metric system
Units of Metric Measurement Length: linear distances
Millimeter (mm); centimeter (cm); meter (m); kilometer (km)
Mass: the measure of how much matter something has Matter is defined as anything that
takes up space and has mass Gram (g); kilogram (kg); metric ton
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 object
Solids are measured in cubic units (m3) Liquids are measured in milliliters or liters;
mL or L.
Units of Metric Measurement Density: the measure of the amount of
matter that takes up a certain space Mass divided by volume Grams per cubic centimeter (g/cm3)
Time: measured in seconds or minutes Temperature: usually in Celsius
Kelvin is the official SI unit for temperature Absolute zero is -273oC or 0K
Solving a ProblemSolving a Problem1)Identify a Problem2) State Observations
about the problem3) Form a Hypothesis
about the problem (if…then…)
4) Design an Experiment to test the hypothesis
5) Collect Data6) Form a Conclusion7) Retest