Scientific Processes and Methods 1. Observations/Questioning 2. Measuring, Organizing Data, and

Classifying 3. Hypothesizing -- a testable explanation

based on experience, reading, and/or previous experiments. (NOT A GUESS)

4. Predicting -- stating in advance the result that will be obtained from testing

Scientific Method, cont. 5. Experimenting -- A controlled procedure

for testing a hypothesis• Control Group -- all conditions remain constant• Experimental Group -- same as control, except

for ONE factor• Variable

• Independent Variable - condition that changes

• Dependent Variable - response to changed condition

• Data• Qualitative ~ descriptive

• Quantitative ~ numbers

Scientific Method, cont.

6. Analyzing Data

7. Inferring Conclusions (concluding from evidence collected during experimentation)

8. Modeling and Communicating

9. Test and Re-test ~ law or theory formed

Scientific Method, cont. LAW -- general statement that describes a

wide variety of phenomena• If a hypothesis describes HOW things happen

and continues to be supported by evidence, it becomes a law.

THEORY -- most probable explanation for a set of data based on best available evidence• If a hypothesis describes WHY things happen

and continues to be supported by evidence, it becomes a theory.

Scientific Method -- Example

Observations:• Fish populations in Twin Lakes are declining.

• The pH (acidity) of the water in the lakes is dropping to 4.2.

• One hundred miles west of Twin Lakes is a power plant that is burning tons of coal every year, releasing sulfur dioxide into the air.

Problem

West Branch

Twin Lakes -- Acid Rain Problem

East Branch

Power Plant

100 miles

Questioning/Hypothesizing

Question: Is there a link between the power plant, the pH of the lake, and the fish decline?

Hypothesis: If acid rain falling on Twin Lakes is related to fish reproduction, then increasing acid rain amounts will cause the fish to have poor reproduction.

Experiment

Experiment• Twin Lakes is a lake in the mountains that can

be divided by a barrier.• A complete inventory will gather baseline data.• One arm of the lake, on the east side of the

barrier, will be treated with sulfuric acid to reduce the pH to 4.0.

• The west arm of the lake will be left alone, other than monitoring.

Experiment

West Branch

Twin Lakes -- Acid Rain Problem

East Branch

Power Plant

100 miles

No Acid Added Acid Rain Added

Barrier

Results

East Branch: • Fish stop reproducing.

West Branch: • No change in fish reproduction.

Conclusion

The power plant emits sulfur dioxide into the air which combines with rain to produce acid rain. The addition of this acidic rain to the lakes lowers the pH and causes the fish to stop reproducing. This results in declining fish populations and jeopardizes the survival of the fish.