Hypotheses, Theories, and Laws

A statement that generalizes a quantity of experimentally observable phenomena is called a scientific law. For example, if a person drops a pencil, it falls downward. This result is predicted by the law of gravity. A generalization that attempts to explain why certain experimental results occur is called a hypothesis. When a hypothesis is accepted as true by the scientific community, it is then called a theory. One of the most important scientific laws is the law of conservation of mass During any process (chemical reaction, physical change, or 

EXAMPLE 1.3. When a piece of iron is left in moist air, its surface gradually turns brown and the object gains mass. Explain this phenomenon. 

The brown material is an iron oxide, rust, formed by a reaction of the iron with the oxygen in the air. 

The total mass of the ash plus the carbon dioxide and the water vapor is equal to the total mass of the log plus the oxygen. As always, the law of conservation of matter is obeyed as precisely as chemists can measure. The law of conservation of mass is fundamental to the understanding of chemical reactions. Other laws related to the behavior of matter are equally important, and learning how to apply these laws correctly is a necessary goal of the smdy of 

Homogeneous. They look alike throughout the sample because they are alike throughout the sample. 

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Scientists have gathered so much data that they must have some way of organizing information in a useful form. Toward that end, scientific laws, hypotheses, and theories are used. These forms of generalization are introduced in Sec. 1.7. 

Symbols, introduced in Section 1.4, are used to represent the elements. The periodic table, introduced in Section 1.5, groups together elements with similar properties. Chemical symbols and the periodic table are both designed to decrease the effort required to learn a great deal of chemistry. Section 1.6 presents scientific laws, hypotheses, and theories that generalize and explain natural phenomena. 

Classification of Matter Representation of Elements Laws, Hypotheses, and Theories Solved Problems... 

Laws, hypotheses, and theories ah give rise to predictions that can be tested by experiments, carefuhy controhed procedures designed to produce critical new observations. If scientists cannot confirm the predictions, they must modify or replace the law, hypothesis, or theory. 

It is the role, and the privilege, of a scientist to study Nature and to seek to unlock her secrets. To unlock these secrets, a certain process is customarily taken. Normally, the scientific process starts with observations the scientist observes some part of the natural world and attempts to find patterns in the behaviors observed. These patterns, when they are uncovered out of what may otherwise be a quite complicated set of events, are then called the laws of behavior for the particular part of nature that has been scrutinized. But the process does not stop there. Scientists are not content merely to observe nature and catalog her patterns—they seek explanations for the patterns. The possible explanations that scientists propose take the form of hypotheses and theories— models —about how things work behind the scenes of outside appearance. This book is about one such type of model and how it can be used to understand the patterns of chemistry. 

Scientific method (Section 6 6) A systematic approach to es tabhshmg new knowledge m which observations lead to laws laws to theories theories to testable hypotheses and hypotheses to expenments... 

It may be useful, I think, to start this discussion not by considering what professional philosophers (to which community, the reader will by now have recognized, the author obviously does not belong) mean by the terms, hypotheses, models, theories, laws, and explanations but, rather, by reviewing what we teach beginning chemistry students. These are the foundations on which most practicing chemists have built their understanding of their science. I excerpt below the relevant material from some popular freshman chemistry books. 

The scientific method works most rigorously when it identifies observations that are incompatible with current hypotheses. Faced with a new observation, scientists list all hypotheses that might explain it and then discard those that are incompatible with accepted physical law. Hypotheses that are not discarded as incompatible remain possibilities. If only one remains, it is promoted to theory. If disproving all hypotheses but one is not possible, we may retreat to demonstrating compatibility with theory, recognizing that compatibility is weaker than proof. In science, we use the phrases I think. . . and I believe. . . as synonyms, both implying .. . based on known physical law. In other words, This theory accommodates all the observations that we currently know. ... 

The scientific method is a systematic approach to research that begins with the gathering of information through observation and measurements. In the process, hypotheses, laws, and theories are devised and tested. 

Scientific hypotheses, when dealing with a scale large enough, are also called theories. And theories are tentative explanations for events that await further substantiating evidence. As evidence accumulates to support a theory, it becomes trausformed into a law, or principle. However, just as there are no absolutely complete works, there are no laws that are completely... 

Scientific method A systematic approach to establishing new knowledge in which observations lead to laws, laws to theories, theories to testable hypotheses, and hypotheses to experiments. 

The scientific method is a systematic approach to research that begins with the gathering of information through observation and measurements. In the process, hypotheses, laws, and theories are devised and tested. Chemists study matter and the substances of which it is composed. All substances, in principle, can exist in three states solid, liquid, and gas. The interconversion between these states can be effected by a change in temperature. The simplest substances in chemistry are elements. Compounds are formed by the combination of atoms of different elements. Substances have both unique physical properties that can be observed without changing the identity of the substances and unique chemical properties that, when they are demonstrated, do change the identity of the substances. 

The Scientific Method Chemists employ the scientific method, which makes use of observations, hypotheses, laws, theories, and experiments. Observations involve measuring or observing some aspect of nature. Hypotheses are tentative interpretations of the observations. Laws summarize the results of a large number of observations, and theories are models that explain and give the underlying causes for observations and laws. Hypotheses, laws, and theories must be tested and validated by experiment. If they are not confirmed, they are revised and tested through further experimentation. 

Scientific laws summarize and predict behavior, but they do not explain the underlying cause. A hypothesis is an initial attempt to explain the underlying causes of observations and laws. A hypothesis is a tentative model (educated by observation) that is then tested by an experiment, a controlled observation specifically designed to test a hypothesis. One or more confirmed hypotheses (possibly with the additional support of observations and laws) may evolve into an overarching model of reality called a theory. A good theory often predicts behavior far beyond the observations and laws from which it was formulated. For example, John Dalton, an English chemist, used the law of conservation of mass along... 

The scientific method refers to the general sequence of activities— observation, experimentation, and the formulation of hypotheses, laws, and theories—that lead to the advancement of scientific knowledge. 

Not all scientific statements are testable hypotheses, laws or theories. For example, scientific paradigms, by one definition (Masterman, 1970 Horgan, 1996), are organizing principles which encompass much of the work of ordinary science, in the language of Thomas Kuhn (1970) but are not necessarily testable. Ordinary science is not the source of revolutionary science (except, possibly when it breaks down) and is not hypothesis driven so much as driven by the requirement to fill in the holes opened in a field by the scientific paradigm. 

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