scientific method pp chem i

Scientific MethodScientific Method

Put the steps in order…

Analyze Data Ask a Question

Experiment Hypothesis

Observation/ResearchConclusion

Theory

Scientific Law

Steps in the Scientific Steps in the Scientific MethodMethod

Observation Observation (ask (ask question)question)

HypothesisHypothesis ExperimentExperiment Analyze DataAnalyze Data ConclusionConclusion TheoryTheory Scientific LawScientific Law

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

heating CuCOheating CuCO33 a a gas is released.gas is released.

ObservationsObservations

Another Another exampleexample of an of an observationobservation

might be might be noticing that noticing that

every time that every time that your sister your sister

blows a bubble blows a bubble bigger than her bigger than her head, it POPS!head, it POPS!

HypothesisHypothesis

A suggested A suggested solution to the solution to the problem.problem.

Must be Must be testabletestable

PredictsPredicts an an outcomeoutcome

HypothesisHypothesis

An An example of a example of a hypothesishypothesis might be that might be that the bubble pops the bubble pops because of the because of the quality of the quality of the gum.gum.

ExperimentExperiment

A A procedure procedure to to testtest the the hypothesishypothesis

..

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 test test ONE ONE variable!variable!

What is the Purpose of What is the Purpose of a Control?a Control?

Controls are NOT being tested

Controls are used for COMPARISON

EXAMPLE: What variables does one need to

account for if one were to design an experiment to test whether or not hot water dissolves salt faster than cold water? What would be the control?

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 in What are the Variables in Your Experiment?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.

One more thing… it is best to make several trials with each independent variable.

How About Another Example? Pumpkin growers would like to

know if phosphorus has a key role in growing GIANT PUMPKINS!

THINK: How would you set up a controlled experiment?

Remember:Remember:

Two groups are used: the control & experimental

groups

There should be only one variable tested at a time.

Perform multiple trials

DataData Results of

the experiment

May be quantitative (numbers) or qualitative

DataData Must be

organized Can be

organized into charts, tables, or graphs

ConclusionConclusion

The answer to the hypothesis based on the data obtained from the experiment

RetestRetest

In order to verify the results,

experiments must be retested.

Theory Vs. Law supported by

many experiments.

can be modified Ex. - Einstein's

Theory of Relativity, Atomic Theory

•Summarizes a pattern in nature. •No known exceptions occur.•Ex. - Law of Universal Gravitation, Law of Conservation of Mass, Gas Laws

Ticket-Out-The-Door: CP You want to buy a new car. You are

interested in three different models (model 1, model 2, model 3). Today you are test driving the cars, and you want the car with the best gas mileage.

Independent Variable: Dependent Variable:

Ticket-Out-The-Door: CPHWithin a classroom setting, subjects were asked to listen to a guest instructor. All subjects were given a description of the instructor. Some subjects read a description containing the phrase “People who know him consider him to be a rather cold person...”, while other people read a description where the word “warm” was substituted for the word cold (otherwise, the descriptions were identical). After the lecture, subjects were asked to rate the instructor. Subjects who were told the instructor was warm gave him more favorable ratings compared to subjects who were told that the instructor was cold.