Scientific MethodScientific Method

Basic StepsBasic Steps

DefinitionDefinition►Scientific method: Scientific method:

basic steps that basic steps that scientists follow in scientists follow in order to order to investigate a investigate a natural natural occurrence.occurrence.

Steps of Scientific MethodSteps of Scientific Method► State the problem or ask a questionState the problem or ask a question► Gather information through observations or Gather information through observations or

research and develop a hypothesisresearch and develop a hypothesis► Perform an experiment to see whether the Perform an experiment to see whether the

suggested answer makes sensesuggested answer makes sense► Record and analyzing the results of Record and analyzing the results of

experiments or other observationsexperiments or other observations► State conclusionsState conclusions► Share resultsShare results

Stating the ProblemStating the Problem►Develop a question or problem that can be solved Develop a question or problem that can be solved

through experimentation.through experimentation.

What invisible trail does a rattlesnake follow in tracking What invisible trail does a rattlesnake follow in tracking down its bitten prey?down its bitten prey?

Gathering InformationGathering Information► Make observations and Make observations and

research your topic of interest.research your topic of interest. A rattlesnakes eyes are only sensitive to visible lightA rattlesnakes eyes are only sensitive to visible light A pair of organs located under the eyes detect A pair of organs located under the eyes detect

invisible light in the form of heatinvisible light in the form of heat A rattler’s tongue “smells” certain odors in the airA rattler’s tongue “smells” certain odors in the air The sight or smell of an unbitten animal does not The sight or smell of an unbitten animal does not

trigger the rattler’s tracking actiontrigger the rattler’s tracking action

HypothesisHypothesis►Predict a possible answer to the problem or Predict a possible answer to the problem or

question. This should be testable.question. This should be testable. After the snake wounds its victim, the snake After the snake wounds its victim, the snake

follows the smell of its own venom to locate the follows the smell of its own venom to locate the animalanimal

ExperimentExperiment►Develop and follow a procedure. Develop and follow a procedure.

Include a detailed materials list. Include a detailed materials list. The outcome must be The outcome must be measurable (quantifiable).measurable (quantifiable). Experiment: Drag a dead mouse that has been Experiment: Drag a dead mouse that has been

struck and poisoned by a rattlesnake along a struck and poisoned by a rattlesnake along a curved path on the bottom of an empty cage. Place curved path on the bottom of an empty cage. Place the snake in the cage and observe the snake’s the snake in the cage and observe the snake’s behavior.behavior.

Control: Control: Drag an unbitten dead mouse along the Drag an unbitten dead mouse along the path. Place the snake in the cage and observe the path. Place the snake in the cage and observe the snake’s behavior.snake’s behavior.

Recording and Analyzing Recording and Analyzing DataData

►Collect and record the data Collect and record the data and analyze results. and analyze results. Modify the procedure if needed.Modify the procedure if needed. Confirm the results by retesting.Confirm the results by retesting. Include tables, graphs, and Include tables, graphs, and

photographs. Do the photographs. Do the experiment many timesexperiment many times

ConclusionConclusion► Make a statement that accepts Make a statement that accepts

or rejects the hypothesis. Make or rejects the hypothesis. Make recommendations for further recommendations for further study and possible study and possible improvements to the procedure.improvements to the procedure. The scent of venom was the only factor The scent of venom was the only factor

that could cause a rattlesnake to follow that could cause a rattlesnake to follow its bitten victim.its bitten victim.

Communicate the ResultsCommunicate the Results►Compile the data and results of Compile the data and results of

your experiment in a lab report, or your experiment in a lab report, or some other presentation format.some other presentation format. Be prepared to present the project Be prepared to present the project

to an audience.to an audience. Expect questions from the audience.Expect questions from the audience.

Factors in an Factors in an experimentexperiment

Controls and variablesControls and variables

Variables in experimentsVariables in experiments► Experiments demand control. If more Experiments demand control. If more

than one variable changes at a time, than one variable changes at a time, the cause and effect is unclear.the cause and effect is unclear.

Experimental VariableExperimental Variable►The variable that you are studying The variable that you are studying

(changing) in and experiment. It is the (changing) in and experiment. It is the only variable that should differ from only variable that should differ from trial to trial.trial to trial.

►This factor is called either the This factor is called either the manipulated variable or the manipulated variable or the independent variable.independent variable.

ControlControl►The variables that you control (don’t The variables that you control (don’t

change) in an experiment. The control change) in an experiment. The control variables are all other variables than variables are all other variables than the experimental variable.the experimental variable. If you are running multiple trials, you will If you are running multiple trials, you will

want to keep all factors the same from want to keep all factors the same from trial to trial except for the thing that you trial to trial except for the thing that you are testing.are testing.

experimental resultsexperimental results►The change that is caused by the The change that is caused by the

experimental variable is called the experimental variable is called the dependent variable or the responding dependent variable or the responding variable.variable.

ExampleExample You want to know how speed affects gas You want to know how speed affects gas

mileage. Speed is the only variable that mileage. Speed is the only variable that should change. The car, tires, road, and should change. The car, tires, road, and wind speed should stay the same. If any wind speed should stay the same. If any of these things differ from trial to trial, of these things differ from trial to trial, then you cannot be certain that the speed then you cannot be certain that the speed caused the difference in gas mileage.caused the difference in gas mileage.

►What is the manipulated variable?What is the manipulated variable? the speed of the carthe speed of the car►What is(are) the controlled variables?What is(are) the controlled variables? the car, tires, road, and wind speed/direction.the car, tires, road, and wind speed/direction.►What is the responding variable?What is the responding variable? the gas mileagethe gas mileage

Graphing Graphing Experimental DataExperimental Data

DRY MIXDRY MIX

DRY MIXDRY MIXD - dependent variableD - dependent variableR - responding variableR - responding variableY - y axisY - y axis

M – manipulated variableM – manipulated variableI – independent variableI – independent variableX – x axisX – x axis

graphinggraphing►The experimental variable is graphed The experimental variable is graphed

on the x-axis (the bottom of the graph)on the x-axis (the bottom of the graph)►The responding data is graphed on the The responding data is graphed on the y-axis ( the vertical axis) y-axis ( the vertical axis)

ExampleExampleCar speedCar speed Fuel efficiencyFuel efficiency

55 10 mpg10 mpg1515 23 mpg23 mpg2525 28 mpg28 mpg3535 29 mpg29 mpg4545 30 mpg30 mpg5555 31 mpg31 mpg6565 28 mpg28 mpg7575 24 mpg24 mpg

What goes where?What goes where?►Remember DRY MIXRemember DRY MIX►What is your Manipulated Variable?What is your Manipulated Variable?►Where should you graph it?Where should you graph it?►What is your Responding Variable?What is your Responding Variable?►Where should you graph it?Where should you graph it?

What is your Manipulated Variable?What is your Manipulated Variable?Where should you graph it?Where should you graph it?

What is your Responding Variable?What is your Responding Variable?Where should you graph it?Where should you graph it?

Plot the dataPlot the data

The Metric SystemThe Metric SystemSI unitsSI units

Metric historyMetric history Before the eighteenth century, there were many Before the eighteenth century, there were many

units of measurement. The lack of common units of measurement. The lack of common standards led to a lot of confusion and significant standards led to a lot of confusion and significant inefficiencies in trade between countries. inefficiencies in trade between countries. Example: length could be measured in feet, inches, miles, Example: length could be measured in feet, inches, miles,

spans, cubits, hands, furlongs, palms, rods, chains, spans, cubits, hands, furlongs, palms, rods, chains, leagues, and more leagues, and more

► The metric system, also known as the Système The metric system, also known as the Système International d'Unités (SI), was developed in the International d'Unités (SI), was developed in the late 1700s to standardize units of measurement in late 1700s to standardize units of measurement in Europe. Europe.

► The metric system is almost always used in The metric system is almost always used in scientific measurement. scientific measurement.

Metric System UnitsMetric System Units►There is only one unit of measurement There is only one unit of measurement

(or base unit) for each type of (or base unit) for each type of measurement. measurement.

►The three base units in the metric The three base units in the metric system are: system are: Length – meterLength – meter Volume - literVolume - liter Mass – gramMass – gram

Measuring liquidsMeasuring liquids►Liquids cling o the edges of glass Liquids cling o the edges of glass

containers, causing a curved surface. containers, causing a curved surface. This curvature is called the meniscus. This curvature is called the meniscus. You measure the level at the horizontal You measure the level at the horizontal center or inside part of the meniscus center or inside part of the meniscus

► 1 mL = 20 drops (eyedropper)1 mL = 20 drops (eyedropper)► 1 L = ½ of a 2 liter soda1 L = ½ of a 2 liter soda► 1 ml = 1 cm1 ml = 1 cm³³

Measuring lengthMeasuring length

►Metric rulers are easy to read. They deal Metric rulers are easy to read. They deal with centimeters and millimeters only so with centimeters and millimeters only so You wont have figure out fractions. You wont have figure out fractions.

►The larger lines with numbers are The larger lines with numbers are centimeters, and the smaller lines are centimeters, and the smaller lines are millimeters. Since millimeters are 1/10th millimeters. Since millimeters are 1/10th of a centimeter, if you measure 7 marks of a centimeter, if you measure 7 marks after a centimeter, it is 1.7 centimeters after a centimeter, it is 1.7 centimeters long.long.

►Be sure that you begin measuring from Be sure that you begin measuring from the beginning of the ruler markings.the beginning of the ruler markings.

Metric sub-unitsMetric sub-units

►The metric system is a decimal-based The metric system is a decimal-based system based on multiples of ten. system based on multiples of ten.

►The subunits are used when measuring The subunits are used when measuring very large or very small things. very large or very small things.

►Any measurement given in one metric Any measurement given in one metric unit can be converted to another metric unit can be converted to another metric unit simply by moving the decimal place. unit simply by moving the decimal place.

Converting Metric UnitsConverting Metric Units► If you are converting from a smaller to a If you are converting from a smaller to a

larger unit, move the decimal place to the larger unit, move the decimal place to the left in the number you are converting. left in the number you are converting.

► If you are converting from a larger to a If you are converting from a larger to a smaller unit, move the decimal to the smaller unit, move the decimal to the right. right.

►The number of places you move the The number of places you move the decimal corresponds to the number of decimal corresponds to the number of rows you are crossing in the table. rows you are crossing in the table.

►Example: someone says that that you Example: someone says that that you have to walk 8,939.0 millimeters to have to walk 8,939.0 millimeters to get to the grocery store. Is this a long get to the grocery store. Is this a long walk?walk?

Quick AssessmentQuick Assessment►What is the basic unit of mass?What is the basic unit of mass?►What is the basic unit of volume?What is the basic unit of volume?►What is the basic unit of length?What is the basic unit of length?►The metric systems is based on units The metric systems is based on units

of:of:►Measurements can be converted from Measurements can be converted from

one unit to another by:one unit to another by: