Scientific Method Nature of Science

A Lost Child Keeping Warm Once upon a time a small child became lost. Because the weather was cold, he decided to gather material for a fire. As he brought objects back to his campfire, he discovered that some of them burned and some of them didn’t burn. To avoid collecting useless substances, the child began to keep track of those objects that burned and those that did not. He proposed a possible “generalization.” Perhaps: “Cylindrical objects burn.” Fable: A Lost Child Keeping Warm Once upon a time a small child became lost. Because the weather was cold, he decided to gather material for a fire. As he brought objects back to his campfire, he discovered that some of them burned and some of them didn’t burn. To avoid collecting useless substances, the child began to keep track of those objects that burned and those that did not. He proposed a possible “generalization.” Perhaps: “Cylindrical objects burn.” This procedure if one of the elementary logical thought processes by which information is systematized. It is called inductive reasoning (a general rule is framed on the basis of a collection of individual observations (or facts)). Using his generalization, the boy gathered more substances to burn. He collected three pieces of pipe, two ginger ale bottles, and the axle from an old car, while leaving a huge cardboard box full of newspapers. During the long cold night that followed he drew these conclusions: (1) The cylindrical shape of a burnable object may not be intimately associated with its flammability after all. (2) Even though the “cylindrical” rule is no longer useful, tree limbs, broom handles, pencils, and other burnables still burn. (3) He’d better bring the list along tomorrow. New idea: Perhaps “Wooden objects burn.” This procedure if one of the elementary logical thought processes by which information is systematized. It is called inductive reasoning (a general rule is framed on the basis of a collection of individual observations (or facts)). Jaffe, New World of Chemistry, 1955, page 3-4

“Cylindrical Objects Burn” WILL BURN WON’T BURN Tree limbs Broom handles Pencils Chair legs Flagpoles Rocks Blackberries Marbles Paperweights Fable: A Lost Child Keeping Warm Once upon a time a small child became lost. Because the weather was cold, he decided to gather material for a fire. As he brought objects back to his campfire, he discovered that some of them burned and some of them didn’t burn. To avoid collecting useless substances, the child began to keep track of those objects that burned and those that did not. He proposed a possible “generalization.” Perhaps: “Cylindrical objects burn.” This procedure if one of the elementary logical thought processes by which information is systematized. It is called inductive reasoning (a general rule is framed on the basis of a collection of individual observations (or facts)). Using his generalization, the boy gathered more substances to burn. He collected three pieces of pipe, two ginger ale bottles, and the axle from an old car, while leaving a huge cardboard box full of newspapers. During the long cold night that followed he drew these conclusions: (1) The cylindrical shape of a burnable object may not be intimately associated with its flammability after all. (2) Even though the “cylindrical” rule is no longer useful, tree limbs, broom handles, pencils, and other burnables still burn. (3) He’d better bring the list along tomorrow. New idea: Perhaps “Wooden objects burn.” Jaffe, New World of Chemistry, 1955, page 3-4

Using his generalization, the boy gathered more substances to burn. He collected three pieces of pipe, two ginger ale bottles, and the axle from an old car, while leaving a huge cardboard box full of newspapers. During the long cold night that followed he drew these conclusions: (1) The cylindrical shape of a burnable object may not be intimately associated with its flammability after all. (2) Even though the “cylindrical” rule is no longer useful, tree limbs, broom handles, pencils, and other burnables still burn. (3) He’d better bring the list along tomorrow. It is important to realize that generalizations have limited use. You can easily overextend a generalization so that it is of little use or it becomes incorrect. Scientists must simplify explanations to make complex ideas more clear. Exceptions always occur when you oversimplify. Scientists must be willing to modify their explanations (theories) when new evidence is uncovered that contradicts their previous explanation. A dogmatic approach, where a person is unwilling to change their ideas when new evidence is uncovered would be an example of bad science. New idea: Perhaps “Wooden objects burn.” Jaffe, New World of Chemistry, 1955, page 3-4

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. You walk into a room and notice that the lights will not come on. Use the scientific method to figure out why. Observation: Hypothesis: Experiment: Conclusion: (Repeat as necessary) 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.

Using the scientific method requires that one be a good observer. Observation Inference uses the five senses involves a judgment or assumption The dandelions in a lawn grow very short. The dandelions in the tall grass by a lawn will grow tall. Give a reasonable hypothesis and an inference for the above observation:

This image looks 3-D and appears to waver across the page.

Perception of Motion http://www.sapdesignguild.org/resources/optical_illusions/images/motion_sm.jpg

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, all other factors must remain constant. (Constants) The conclusion must be based on the DATA, if it is not, then it is an inference and not a valid conclusion

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

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.

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.

Four Element Theory Plato was an atomist Thought all matter was composed of 4 elements: Earth Water Fire Air Ether (close to heaven) FIRE Hot Wet Cold Dry ‘MATTER’ AIR EARTH THE SCEPTICAL CHYMIST (1661) “The Greeks believed that earth, air, fire, and water were the fundamental elements that made up everything else. Writing in 1661, Robert Boyle (1627-1691) argued against this idea, paving the way for modern ideas of the elements. He defined an element accurately as a substance that could not be broken down into simpler substances.” Eyewitness Science “Chemistry” , Dr. Ann Newmark, DK Publishing, Inc., 1993, pg 18 Boyle rejected the notion of “qualities” of prime matter. Rather, he believed that there were many different kinds of matter. An “element” is a piece of matter that is not made from anything else. The Greek thinker Empedocles first classified the fundamental elements as fire, air, earth, and water, although our particular diagram reflects Aristotle's classification. WATER Relation of the four elements and the four qualities Graphic courtesy of Ken Costello @ www.chemistryland.com

Scientific Method and Law Step 1: Observe: state the problem and gather all available information on it. observations: see things in the world, read books, ask an expert. Step 2: propose a hypothesis: a testable, reasonable explanation of an event, an educated guess based on all the best data collected up to that point. Usually stated in the form “If…then” Step 3: TEST THE HYPOTHESIS BY CONDUCTING CONTROLLED EXPERIMENTS EXPERIMENTS: Involve changing one variable at a time and noting the effect that change has. VARIABLE – any factor that could influence the outcome of an event. e.g. Referee, crowd, amount of oxygen available, temperature, wind In a controlled experiment , the variables are changed one at a time. After each variable is changed, scientists note the effect that particular variable is having on the results of the experiment. It is often difficult to isolate variables in an experiment. Scientists must make assumptions that may prove incorrect later. A synergistic effect may be observed where the variable interact in unexpected ways. 1 + 1 = 3! experiments require DATA – the results of the experiment; a collection of measurements. Step 4: draw a valid conclusion – follows from results of the experiments, not personal prejudices. Conclusions must be supported by data in order to be valid. Theory vs. Law A hypothesis that withstands repeated testing may become part of a theory. Theory – an explanation of an observation based on many experiments and logic. Tries to explain WHY something happens. Theories undergo revision, and are occasionally thrown out altogether. Atomic theory, theory…gravity, evolution, relativity Explaining observed facts of nature with theories involves using models. Four element theory…fire, water, earth, air composed all matter. Models help us simplify what we are trying to study. Separate the important from the unimportant, and concentrate on the important. Understanding and clarity require simplification (I.e. “what did you do today?”) A Law of nature state what happens “Nature if THIS way…” we DO NOT REVISE LAWS we have never observed a single instance in which a law of nature has been violated.

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