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Introduction to Chemistry

The Scientific Method

The scientific method includes asking a question, doing background study, formulating a hypothesis, experimenting, analyzing results, confirming or correcting the hypothesis, and reporting the results.

The scientific method is a systematic procedure used by scientists to conduct research consisting of observation, measurement, and experimentation and the formulation, testing, and modification of hypotheses. It includes steps scientists use that are performed iteratively to support or refute a hypothesis.

1. Make observations: Observing matter and how it changes is the first step of any investigation. Scientists may observe a naturally occurring phenomenon or may conduct experiments with suitable precautions to study a phenomenon. Also, observations can be qualitative, quantitative, or both. A qualitative observation does not include measurement or mathematical analysis. For example, the element sulfur is yellow. A quantitative observation includes measurement or mathematical analysis. For example, 736 grams of the compound copper sulfate dissolve in one kilogram of water at 100 degrees Celsius.

2. Ask a question: Observations can lead to questions that help frame the context of the investigation. For example, the observation of water boiling at a low temperature in low-pressure areas can lead to the question, "What is the effect of pressure on the boiling point of water?"

3. Research existing data: Scientists often research existing data that is relevant to the question. Information is gathered from various sources so it can be studied and compared. This provides a basis to form a hypothesis that can possibly explain the data.

4. Form a hypothesis: A hypothesis is a prediction based on a limited number of observations. It provides a possible explanation for a phenomenon. It is a kind of educated guess based on appropriate data. For example, consider the statement, "At decreased air pressure, the boiling point of water decreases." This statement is a hypothesis formed after observing water boiling at high elevations. A hypothesis should be formed in such a way that experiments can be designed to test it.

5. Design and perform an experiment: Experiments are designed to test a hypothesis, and they are carefully planned and performed. Proper precautions must be taken, and all findings should be recorded. In most cases, experiments are repeated to account for possible errors. The results of repeated experiments are averaged together to account for differences in individual results.

6. Analyze results: Care must be taken to remove uncertainties and errors.

7. Draw conclusions: Appropriate conclusions are drawn from the analysis.

8. Accept hypothesis: The hypothesis is accepted or modified based on the analysis. A properly designed experiment, when executed correctly, will give information to scientists about whether the hypothesis is valid. If the hypothesis is valid, further investigation is performed to verify it. The hypothesis may also be modified based on the experimental results and again tested through further experimentation.

9. Report results: If the hypothesis seems to explain the experimental results correctly, further analysis is done, and more experiments are performed to authenticate it.

The process often entails many revisions and may not be as straightforward as depicted. Procedures, data, analysis, and results must be clearly communicated so that the work can be peer reviewed, or reviewed by scientists knowledgeable in the subject, and replicated for verification. Eventually, after much research by separate individuals, results may be formulated as a theory or stated as a law. A law is a statement of what happens under certain conditions that is verified by multiple experiments. A law is found to always hold true. For example, there are no exceptions to the law of universal gravitation, which states that attractive forces exist between all objects. A theory is a well-substantiated and experimentally verified explanation that describes phenomena. Theories are subject to new investigation and modification. Atomic theory, which states that matter is made up of discrete particles called atoms, has taken several centuries and much experimentation to develop. It has been, and continues to be, modified. Both laws and theories must be well tested to be accepted as valid.

Scientific Method

A flowchart of the scientific method depicts the steps involved in the systematic procedure often used in scientific investigations.
Historically, many scientists have used the scientific method to answer questions about the natural world. For example, Polish mathematician and astronomer Nicolaus Copernicus (1473–1543) made observations of the night sky and the way the movement of the stars and planets across the sky. Based on his observations, he put forward the question of whether Earth is the center of the solar system. He observed the astronomical data and researched it. Based on the experimental data of his era and from the analysis of the data, he constructed a hypothesis, proposing that the sun is the center of the system and that all the planets move around it in circles. In 1543 a book in which Copernicus outlined his model of the solar system was published. At that time, geocentric theory, which said that Earth was the center of the solar system and all planets and the sun revolve around it, was held as true.

The model Copernicus proposed revolutionized astronomy. A detailed study of the solar system was made by several eminent astronomers later in the 16th century. German astronomer Johannes Kepler (1571–1630) also made observations of the movement of the stars and planets in the night sky. His observations led him to question whether Copernicus’ hypothesis was correct. After extensive research, Kepler accepted the hypothesis, but based on his observations, he modified the hypothesis by stating that the planets revolve in elliptical orbits around the sun.

Like Copernicus and Kepler, Italian scientist Galileo Galilei (1564–1642) also made observations of the night sky that led him to wonder about the objects in the sky and the way they move. Because of these questions, he began to research the night sky and was the first to use a telescope to directly observe planetary motion. These observations were solid evidence for the heliocentric theory. Since that time, further scientific advancements, photographs, and measurements have led to the refinement of the heliocentric theory, which describes the solar system with the sun at the center and all the planets revolving around it in elliptical orbits.