http://www.ck12.org Chapter 1. Introduction to Chemistry
general principle you begin with must be true. I can only conclude that vinegar is an acid based on the accuracy of
the general principle that acids turn blue litmus paper red.
Inductive and deductive reasoning can be thought of as opposites. For inductive reasoning, we start with specific
observations and draw a general conclusion. For deductive reasoning, we start with a general principle and use this
principle to draw a specific conclusion.
The Idea of the Experiment
Inductive reasoning is at the heart of what we call thescientific method. In European culture, this approach was
developed mainly by Francis Bacon (1561-1626), a British scholar. He advocated the use of inductive reasoning in
every area of life, not just science. The scientific method as developed by Bacon and others involved several steps:
- Ask a question –identify the problem to be considered.
- Make observations –gather data that pertains to the question.
- Propose an explanation (a hypothesis) for the observations.
- Design and carry out ways to test the hypothesis.
Note that this should not be considered a “cookbook” for scientific research. Scientists do not sit down with their
daily “to do” list and write down these steps. The steps may not necessarily be followed in order, and testing a
given explanation often leads to new questions and observations that can result in changes to the original hypothesis.
However, this method does provide a general outline of how scientific research is usually done.
During the early days of the scientific enterprise (up to the nineteenth century), scientists generally worked as
individuals. They may have had an assistant to help with preparing materials, but their work was usually solitary.
Their results might be disseminated in a letter to friends or at a scientific society meeting. Today the practice of
science is very different. Research is carried out by teams of people, sometimes at a number of different locations.
The details of methods and the results of the experiments are published in scientific journals and books, as well as
being presented at local, national, or international meetings. Electronic publication on the Internet speeds up the
process of sharing information with others.
Before conclusions can be considered reliable, experiments and results must be replicated in other labs. In order for
other scientists to know that the information is correct, the experiments need to be done in other labs to obtain the
same results. Researchers in other labs may get ideas for new experiments that could confirm the original hypothesis.
On the other hand, they may see flaws in the original thinking and experiments that would suggest the hypothesis
was false. The modern scientific approach of carefully recording experimental procedures and data allows results to
be tested and replicated to that everyone can have confidence in the final results.
A good experiment must be carefully designed to test the hypothesis. Let’s think back to our example of inductive
reasoning in observing reactions with alkali metals and water. We believe that all alkali metals produce violent
reactions with water. To test this hypothesis, we must design an experiment in which we can observe the reactions
of each alkali metal with water. We will test each alkali metal: lithium, sodium, potassium, rubidium, cesium, and
francium. In order for this experiment to produce consistent results, we should use the same amount of water and
same size sample of these metals each time a test is formed. Based on our hypothesis, we expect a violent reaction to
occur when any one of these metals is added to water. If a sample of lithium is added to our water and we observe a
small explosion, our hypothesis is strengthened. If lithium is added to our water and nothing happens, our hypothesis
must not be true. We can either modify our hypothesis to include this new data, or replace our hypothesis with a new
one.
When a hypothesis is confirmed repeatedly, it eventually becomes a theory. A theory is a general principle that
is offered to explain a natural phenomenon. A theory offers a description ofwhysomething happens. Although
theories, like hypotheses, can be disproved, it is more likely for a theory to be modified. However, while a hypotheses
is a suggested explanation of a phenomena, a theory is a proved explanation based off of many hypotheses and much
experimentation. Over time, theories evolve with new research and data, but are rarely discarded completely. A