The Scientific MethodChapter 2.1Dr. C.’s PAP Chemistry Fall 2015

Lesson Objectives• Review Scientific Notation

• Describe the purpose and steps of the scientific method

• Distinguish independent, dependent and control variables

• Describe the difference between a hypothesis and theory

• Explain the purpose and use of scientific models

• Define: qualitative, quantitative, system, repetitions, replication

Scientific Method• Logical approach to solving problems

Observation• Observing requires your senses to obtain information (data)

– Data may be:

– Qualitative (descriptive)

– Quantitative (numerical)

• Examples of qualitative data: color or smell

• Examples of quantitative data: mass, volume, length

• A system is a portion of the universe being studied

– Can be as large as a rain forest or as small as the contents of a beaker

Hypothesis

•A Hypothesis is a testable statement.–Often “if-then” statements (But not always!)

–Often called “educated guesses”

Testing a Hypothesis• Testing a hypothesis requires experimentation to

support or refute the hypothesis.

• Controls are the experimental constants, they do not change during the experiment.

• Variables change during the experiment.

– Independent Variable: Manipulated Variable. Usually known to the scientist prior to the experiment.

– Dependent Variable: Responding Variable. Usually unknown to the scientist prior to the experiment.

One experiment isn’t enough!

• Repetition is the expectation of getting the same results when the experiment is repeated under the same conditions.

• Replication is the expectation that other scientists will be able to reproduce your experimental results.

Theory vs. Hypothesis• A theory is a well-substantiated explanation that is

acquired through the scientific method and repeatedly tested and confirmed through both observation and experimentation.

• Although a theory is a well-substantiated explanation, it doesn’t mean it can’t change over time.

During the next chapter we will see some of the changes that have taken place to atomic theory.

Scientific Models

•A model is an explanation of how phenomena occur. –Visual, verbal or mathematical

Lesson Objectives• Describe the purpose and steps of the scientific

method

• Distinguish independent, dependent and control variables

• Describe the difference between a hypothesis and theory

• Explain the purpose and use of scientific models

• Define: qualitative, quantitative, system, repetitions, replication

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