The Scientific Method Chapter 2, section 2-1 p.29-31 Robert Boyle Published The Sceptical Chymist (1661) …stated that scientific speculation was worthless unless it was supported by experimental evidence. This principle led to the development of the scientific method.

Using the scientific method requires that one be a good observer. observation inference uses the five senses involves a judgment or assumption

“My mother the eye doctor” In performing activities and experiments, you make observations. An observation is something you see. There are times when you make judgments or decisions based on your observations. In performing activities and experiments, you make observations. An observation is something you see. There are times when you make judgments or decisions based on your observations. These judgments or decisions are called inferences. Inferences are logical conclusions based on your observations. Look at the cartoon above. Read the statement below the cartoon. Based on what you observe in the cartoon, decide if each statement is an observation or inference. One of the teams is called the “Reds.” Observation or Inference? The adult is holding a piece of paper. One player is a catcher. The mother of the batter is an optometrist or opthalmologist (an eye doctor). The players in the picture are on opposite teams. One player is holding a bat. The adult is the umpire. The player holding the bat is talking. The piece of paper is a note from the mother of the batter. Names are written on the uniforms. One player is wearing a catcher’s mask.

Observations are also called data. There are two types of data. Scientists prefer quantitative data over qualitative data. It is easier to replicate and compare quantitative data. qualitative data quantitative data descriptions; measurements; no numbers must have numbers and UNITS

Parts of the Scientific Method Identify an unknown. Make a hypothesis (a testable prediction). Experiment to test the hypothesis. Draw a valid conclusion.

Hypotheses A tentative explanation for the observations May not be correct, but it puts the scientist’s understanding of the system being studied into a form that can be tested Copyright © 2007 Pearson Benjamin Cummings. All rights reserved.

Experiments Tests the validity of the hypothesis Are systematic observations or measurements made under controlled conditions, in which the variable of interest is clearly distinguished from any others Has control group (lacks the variable you are testing) & experimental group (has the variable you are testing) Experiments are controlled meaning you can only test 1 variable at a time! Tests dependent & independent variables Independent Variable The variable that will be tested Dependent Variable The variable that is affected by the independent variable If experimental results are reproducible, they are summarized in a law. Copyright © 2007 Pearson Benjamin Cummings. All rights reserved.

A Scientific Experiment procedure the order of events in an experiment; the “recipe” variable any factor that could influence the result Experiments must be controlled; they must have two set-ups that must differ by only one variable. The conclusion must be based on the data.

Scientific Method Observations Hypothesis Experimentation Controlled (one variable changed at a time) Collect data (quantitative and qualitative) Analyze data (graph, statistics…trends) Form valid conclusion. After many experiments…form a theory. Recall, our checkbook activity. Each check represented data. As more data was collected it became clearer what had happened. Some bits of data were unimportant. Most likely, you had to modify your theory as new pieces of data were revealed.

Scientific Law vs. Scientific Theory A law states what happens. Law of Gravity A theory tries to explain why or how something happens. You can distinguish between a theory and a law by asking the question: Is the proposal measurable? Yes, the statement is a law. No, it is a theory. Theory of Gravity Atomic Theory Collision Theory of Reactions

Experiments Law Theory – Describes what happens and not why – A verbal or mathematical description of a phenomenon that allows for general predictions – Describes what happens and not why – Unlikely to change greatly over time unless a major experimental error is discovered Theory – Attempts to explain why nature behaves as it does – Is incomplete and imperfect, evolving with time to explain new facts as they are discovered Copyright 2007 Pearson Benjamin Cummings. All rights reserved.

Theory vs. Natural Law Scientific theory Natural law analyze additional data Hypothesis analyze initial observations Experiment

Scientific Method Make observation Ask question Develop hypothesis Test hypothesis with an experiment Test hypothesis with further experiments Revise hypothesis Analyze data and draw conclusions Hypothesis IS supported Hypothesis is NOT supported Develop theory Wysession, Frank, Yancopoulos, Physical Science Concepts in Action, 2004, page 8

Scientific Method An Overview Question Research Hypothesis Procedure/ First What does the scientist want to learn more about? Then Research Gathering of information Scientific Method An Overview Next Hypothesis An “Educated” guess of an answer to the question Then Procedure/ Method Written and carefully followed step-by-step experiment designed to test the hypothesis Next Data Information collected during the experiment And And Observations Written description of what was noticed during the experiment Finally Conclusion Was the hypothesis correct or incorrect?

Stages In The Scientific Method OBSERVING collecting data measuring experimenting communicating FORMULATING HYPOTHESES organizing and analyzing data classifying inferring predicting communicating TESTING predicting experimenting communicating collecting data measuring THEORIZING constructing models predicting communicating PUBLISH RESULTS communicating Data do not support hypothesis – revise or reject hypothesis Results confirmed by other scientists – validate theory. There is an organizational scheme to the scientific method. However, students should be aware that this scheme is NOT a set of procedural steps that are strictly enforced. Why is it so important to present scientific results in a form than can be evaluated by others? (Verification of results is the only way we can have confidence in the findings of scientific research.) Which stages shown involve data? (All stages shown involve data.) What might be wrong if repeated experimentation does not support a hypothesis? (The hypothesis may be incorrect.)

Laws of nature never change. Scientific Law Charles’s Law V1 V2 T1 T2 = Observations Scientific Law Experiments NEED TO CHANGE: picture of balloon over hot water bath (can have mouse over where balloon is small and large),. A scientific law summarizes the results of many observations and experiments. Laws of nature never change.

Theories and Laws The Earth is flat… Speeding kills (Audubon, Germany); seat belts save lives… LAW: 65 mph and wear seat belt No explanation of why…but the theory is if you drive at 120 mph and crash, an ambulance won’t need to be called (only next of kin).