Transcript

Scientific MethodScientific Method

Observations, Inferences, and Observations, Inferences, and Controlled ExperimentsControlled Experiments

Scientific method.Scientific method.•A systematic method of solving A systematic method of solving problems problems

• All scientific knowledge is based on All scientific knowledge is based on accurate observationsaccurate observations of the natural of the natural worldworld..

Step 1 - ObservationsObservation - what is sensed or measured. 

An An ObservationObservation is an act of carefully is an act of carefully watching something and collecting facts. watching something and collecting facts. - Good scientific observations should be:- Good scientific observations should be:

Accurate – Quantify or measure whenever possible

Detailed and Complete – Consider all parts of the observation

Repeatable – All observers see the same thing or each time the event is observed the description is the same

There are two types of observations: There are two types of observations: a) a) QualitativeQualitative Observations Observations—An observation —An observation

that describes the that describes the physicalphysical characteristics or characteristics or qualities of something. qualities of something.

(Ex. The water is hot; The M&M is small; The egg (Ex. The water is hot; The M&M is small; The egg smells bad; The leaf is orange, etc)smells bad; The leaf is orange, etc)

b)b) QuantitativeQuantitative Observations Observations—An observation —An observation

that is based upon numerical information or a that is based upon numerical information or a measurementmeasurement of some type. of some type.

(Ex. The water is 45ºC; The M&M is 1.7 cm in (Ex. The water is 45ºC; The M&M is 1.7 cm in length; The car is traveling at 65 Km/hr)length; The car is traveling at 65 Km/hr)

• Good scientific observations are used in order to makeGood scientific observations are used in order to make predictionspredictions,, or or inferencesinferences, about the natural world. , about the natural world.

• They also allow us to formulate a They also allow us to formulate a HypothesisHypothesis

Step 2 – Form a HypothesisStep 2 – Form a Hypothesis

A possible answer to our question.

Or a possible explanation about an observation.

A Hypothesis should be supported by our observations and logical given our background knowledge.

Step 3 - ExperimentsStep 3 - Experiments

Set of controlled experiments designed to test a hypothesis. leads to new observations,

If experiments do not prove our hypothesis

Do more experiments, or…

Formulate a new hypothesis and start over!

ControlledControlled Experiments Experiments—— An experiment is basically a An experiment is basically a comparisoncomparison of two situations. of two situations.

One of the situations is left One of the situations is left constantconstant, , while one factor of the other situation is while one factor of the other situation is changedchanged in order to test the affect of that in order to test the affect of that specific change. specific change.

ControlControl – a set of conditions used for – a set of conditions used for comparison purposes; can either be original comparison purposes; can either be original conditions, real-life conditions, or specific conditions, real-life conditions, or specific conditions set by the experimenterconditions set by the experimenter

There are There are three typesthree types of factors that may affect an of factors that may affect an experiment. These factors are called experiment. These factors are called variablesvariables. .

1. The factor that is purposely changed by the 1. The factor that is purposely changed by the experimenter is called the experimenter is called the independentindependent variablevariable (also called the (also called the manipulated manipulated variable)variable)..

2. The factor that changes in response to the 2. The factor that changes in response to the independent variable is called the independent variable is called the dependentdependent variablevariable (or the (or the responding variableresponding variable). ).

3. The rest of the factors that the scientists keep 3. The rest of the factors that the scientists keep the same in the experiment are called the the same in the experiment are called the controlled variablescontrolled variables. .

It is important to test the affect of It is important to test the affect of changing changing only only oneone variable variable in order to get accurate in order to get accurate results. results.

****If only one variable is changed and all the If only one variable is changed and all the other factors are kept the same then we other factors are kept the same then we say that it is a controlled experimentsay that it is a controlled experiment. .

***Uncontrolled conditions can lead to ***Uncontrolled conditions can lead to inaccurate resultsinaccurate results!!!!!!!!

Step 4 –Conclusion or Theory

Sometimes the process just ends with a conclusion. Examples – the substance is baking soda,

or the substance is cocaine.

Or a Theory is formulated, A theory is a broad, general explanation

that is developed for why things behave the way they do.

Sometimes a model is developed.Like the model of the atom.

 

Theory vs. LawTheory vs. LawTheory – an explanation that has been supported by many experiments.

Theories are always subject to new discoveries and are modified to include new data. 

Example – The dinosaurs became extinct after a large asteroid hit earth and blocked out all the light.

The true test of a theory is if it can predict new behaviors.

If the prediction is wrong, the theory must be changed.

Scientific LawScientific Law

Scientific Law – Describes a relationship in nature that is supported by many experiments and for which no exception has been found. It is always true.It is always true.

 

Laws are summaries of observations and are often a mathematical relationship.

 

Examples - A gas will expand when heated. Mass and Energy will be conserved.

Observations

Hypothesis

Experiment

Law

Theory(Model)

Prediction

Experiment

Modify

Observations

More Observations


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