Chapter 1:Unit 2. Scientific Method
Scientific Method
1) Knowledge builds when we start to ask a question about an observed fact. The first step in acquiring scientific knowledge is often the Observation or measurement. Some observations are simple, requiring nothing more than the naked eye. Other observations depend on the use of sensitive instrumentation. Occasionally, an important observation happens entirely by chance. Antoine Lavoisier (1743–1794), a French chemist who studied combustion, burned substances in closed containers. He carefully measured the mass of each container and its contents before and after burning the substance inside, and observed that there was no change in the mass during combustion. Lavoisier made an observation about the chemical change.
2) Observations are the starting point that lead to hypotheses or laws. Observations often lead scientists to formulate a hypothesis, tentative interpretation or explanation of the observations. Lavoisier explained his observations on combustion by hypothesizing that combustion involved the combination of a substance with a component of air. A good hypothesis is falsifiable, which means that further testing has the potential to prove it wrong. Hypotheses are tested by experiments, highly controlled observations designed to validate or invalidate hypotheses. The results of an experiment may confirm a hypothesis or show the hypothesis to be mistaken in some way. In the latter case, the hypothesis may have to be modified, or even discarded and replaced by an alternative hypothesis. Either way, the new or revised hypothesis should also be tested through further experimentation.
3) Sometimes a number of similar observations lead to the development of a scientific law, a brief statement that summarizes facts based on previous observations and predicts future ones. For example, based on his observations of combustion, Lavoisier developed the law of conservation of mass, which states, “In a chemical reaction matter is neither created nor destroyed.” This statement came out of Lavoisier’s observations, and it predicted the outcome of similar experiments on any chemical reaction. Laws are also subject to experiments, which can prove them wrong or validate them.
4) One or more well-established hypotheses may form the basis for a scientific theory. Theories provide a broader and deeper explanation for observations and laws. They are models of the way nature is, and they often predict behavior that extends well beyond the observations and laws on which they are founded. A good example of a theory is the atomic theory of John Dalton (1766–1844). Dalton explained the law of conservation of mass, as well as other laws and observations, by proposing that all matter was composed of small, indestructible particles called atoms. Dalton’s theory was a model of the physical world—Scientific theories are also called models
5) Theories are also tested and validated by experiments. If a law, hypothesis, or theory is inconsistent with the findings of an experiment, it must be revised and new experiments must be conducted to test the modified hypotheses. Over time, scientists eliminate inconsistent theories, and better theories that are consistent with experiment only remain. Established theories with strong experimental support are the most powerful pieces of scientific knowledge. People unfamiliar with science sometimes say, “That is just a theory,” as if theories were mere imaginations. However, well-tested theories are as close to truth as we get in science.
