Chapter 2, Section 1: Pages 29-31

What is the scientific method? A systematic approach to problem-solving.

What are the steps of the scientific method? Observation – identify a problem.Observation – identify a problem. Form hypothesis – possible explanation.Form hypothesis – possible explanation. Experiment – to test the hypothesis.Experiment – to test the hypothesis. Conclusion: revisit hypothesis. Does it need to be adjusted?Conclusion: revisit hypothesis. 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 Observations Use words to describe – the color, odor, shape, texture, or some other physical characteristic.

Quantitative Observations Use numbers to describe a property. Result from measurement. Include a number and a unit. –Height, Mass, Temperature

What’s the difference between a fact and an inference? FactsFacts can be verified. They are objective. InferencesInferences are subjective. They involve conclusions drawn from data. –On Friday the 13 th I saw a black cat. –On Friday the 13 th I saw a spooky cat.

Facts vs. Inferences Ice Floats. (Observed fact.) Ice must be lighter than water. Only things lighter than water will float. Careful!Careful!

Experiments variablesMost systems in nature have many variables. (Parameters that can change.) An experiment is an attempt to simplify nature. constant –Hold most variables constant. Independent variable –Manipulate one variable. (Independent variable. Controlled by the scientist.) Dependent variable –Measure one variable. (Dependent variable.)

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 of scientific method. 1Theory (model) 1 - Theory (model) 2 – Law (summary)

Theory 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 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 between a theory and a law again?

Theory vs. Law Attempt to explain why something happens. Summarizes what always 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.