Science begins with the study of phenomenon. A phenomenon is an occurrence, action, or event that we can recognize through use of one or more of our senses. Chemists concern themselves with phenomenon related to matter and changes occurring in it. When phenomenon is being investigated for the first time, they must be described, compared, and classified to establish what we know, or the facts about the phenomenon. Based on these obtained facts about a natural phenomenon, the scientists speculate regarding phenomenon and their behaviour without assumption of its truth. Such a speculation is term as hypothesis. Thus, speculation or supposition made to explain the phenomenon and their behaviour without assumption of its truth is called hypothesis. It is a starting point for investigation and research.
A hypothesis is speculation until it is evaluated experimentally.
To do this, we make predication based upon the hypothesis and devise
experiments to evaluate the predictions.
For example, if the hypothesis is that water is composed of
hydrogen and oxygen, the following set of testable facts can be predicted.
- Hydrogen and oxygen will combine to form water.
- Water will decompose to form hydrogen and oxygen.
- Water will not be formed unless both hydrogen and oxygen are present.
To evaluate the first statement experimentally and find out whether hydrogen and oxygen will combine to form water, we can mix the gases oxygen and hydrogen, ignite the mixture, collect the product of combustion and test for the presence of water.
If facts predicted by a hypothesis are not found in experimentation,
the hypothesis is said to have been rejected. If they are found correct, the
hypothesis is said to have been verified. Thus, when the truth of the
hypothesis is confirmed by experiments, then it becomes Theory. Examples of
theory are, atomic theory, kinetic molecular theory, etc.
A theory is not a permanent conclusion but is changed and modified,
as experimental results are obtained which are not explained by the theory.
Theories are useful in that they allow to anticipate the results of further
experiments and help in the discovery of new phenomenon.
When a theory survives for an extended period without any challenges then it takes the form of LAW. So some generalizations relating to a theory (large bodies of facts) are referred to as law. Laws are seldom rejected; some examples of laws are Boyle's Law Charles Law and Graham's Law.
