Chapter 2, Section 1: Pages 29-31

What is the scientific method?

A systematic approach A systematic approach to problem-solving.to problem-solving.

What are the steps of the scientific

method?• Observation – identify a Observation – identify a problem.problem.

• Form hypothesis – possible Form hypothesis – possible explanation.explanation.

• Experiment – to test the Experiment – to test the hypothesis.hypothesis.

• Conclusion: revisit hypothesis. Conclusion: revisit hypothesis. Does it need to be adjusted?Does it need to be adjusted?

Hypothesis

• Testable, educated guess to explain an observation.

Experiment

• Set of controlled observations to test the hypothesis.

Hypothesis

Observations

Experiments Theory

Scientific Law

Observations are facts you take in with

your senses. They can be

•QualitativeQualitative•QuantitativeQuantitative

Qualitative ObservationsQualitative Observations

•Use words to describe– the color, odor, shape, texture, or some other physical characteristic.

Quantitative ObservationsQuantitative Observations

• Use numbers to describe a property.

• Result from measurement. • Include a number and a unit.

– Height, Mass, Temperature

What’s the difference What’s the difference between a fact and an between a fact and an

inference?inference?• FactsFacts can be verified. They are

objective.• InferencesInferences are subjective. They

involve conclusions drawn from data.– On Friday the 13th I saw a black cat.– On Friday the 13th I saw a spooky cat.

Facts vs. InferencesFacts vs. Inferences

• Ice Floats. (Observed fact.)

• Ice must be lighter than water.

• Only things lighter than water will float.

• Careful!Careful!

Experiments• Most systems in nature have many variablesvariables.

(Parameters that can change.)• An experiment is an attempt to simplify nature.

– Hold most variables constantconstant.– Manipulate one variable. (Independent Independent

variablevariable. Controlled by the scientist.)– Measure one variable. (DependentDependent

variablevariable.)

Control

• Control: Perform the experiment under specific conditions. Standard for comparison.

• Compare the experiment with the control. They should differ by only 1 variable.

Conclusion

• Judgment based on the experimental data.

• Does the experiment confirm the hypothesis or does the hypothesis need to be modified?

2 Long-term outcomes 2 Long-term outcomes of scientific method.of scientific method.

• 11 - Theory (model)Theory (model) • 2 – Law (summary)2 – Law (summary)

Theory or ModelTheory or Model•an overall explanation of

some natural phenomenon. • Ex: Kinetic Theory.

– Supported by many experiments – explains lots of observations

– Can be modified– Can be used to make predictions

Some Theories

• Kinetic Theory• Theory of Natural Selection• Theory of Relativity

Scientific LawScientific Law

•Summary of accepted facts of nature.–Law of Conservation of Energy–Law of Conservation of Mass –Law of Conservation of Charge.

What’s the difference What’s the difference between a theory between a theory and a law again?and a law again?

Theory vs. LawTheory vs. Law

Attempt to Attempt to explain explain whywhy something something happens.happens.

Summarizes Summarizes whatwhat always always happens.happens.

A note about variables…

• Consider the bean plant we discussed in class. Some variables that might influence bean plant growth include:– Amount of sunlight– Amount of water– Amount of nutrients in soil– Elapsed time– Average temperature– Amount of room for root growth

Hypothesis

• The more hours of sunlight a bean plant gets, the higher it will grow.

• Experimental design: We will plant several beans and expose them to different hours of sunlight. We will measure the height of the bean plants at various intervals.

“Fixed” variables

• In this series of experiments, the controlled or independent variable is the number of hours of sunlight the plant got each day and the dependent or responding variable is its height.

• The amounts of water, nutrients, and room for root growth, as well as the average temperature and the time intervals should be the same for all plants in this series of experiments.

Experiments tend to be simpler than nature!

• We can’t vary everything at once, or we couldn’t figure out what was important.