- Describe how the Renaissance period in history changed the approach to science.
- Identify the steps of the scientific method.
- Differentiate between the independent variable and the dependent variable in an experiment.
- Describe how scientists work in research groups and communicate their results.
- control group
- dependent variable
- independent variable
- scientific law
- scientific method
Check Your Understanding
Recalling Prior Knowledge
- How did the ancient practice of alchemy differ from the modern science of chemistry?
- What are the properties of a well-designed scientific experiment?
Advancements in science are not always planned. Many groundbreaking discoveries in the history of science were made almost completely by accident. However, science follows a rigorous, time-tested process called the scientific method. By applying the scientific method, scientists can be ready for whatever results their research gives them, and many new and important discoveries can be made.
It may surprise you to know that science is, relatively speaking, a very young subject. The Renaissance, which occurred roughly between the 14th and 17th centuries, was a time of great upheaval in Europe. The Middle Ages were dominated by a dogmatic approach to knowledge. The Renaissance ushered in new ways of thinking and great advancements in art, music, and culture. There also came a new emphasis on obtaining knowledge through the processes of observation and experimentation, as opposed to a reliance on older ideas that were based on a less rigorous scientific process. Two individuals who personified the Renaissance approach to science are Leonardo da Vinci and Nicolaus Copernicus. Many credit da Vinci with being the father of modern science. He is renowned for his observations and drawings of human anatomy (Figure below). He also set up controlled experiments to investigate water flow, medical dissection, and the systematic study of movement and aerodynamics. Copernicus was an astronomer who suggested, based on observations, a heliocentric model of the solar system, meaning that the Earth and other planets traveled around the Sun. The prevailing doctrine had been that the Earth was the center of the universe and that all celestial bodies must travel around it.
Leonardo da Vinci was a Renaissance artist and scientist who made great advancements in the field of anatomy. On the left is the famous Vitruvian Man drawing. On the right is a document showing the anatomy of the human arm.
More than any one particular piece of knowledge, the Renaissance represented a change in the way human beings thought about the world around them. Emphasis shifted from a philosophical explanation of the world’s natural processes to one that was instead based on observation and experimentation. The process of scientific discovery that we now call the scientific method originated during the Renaissance. This new method led to great advancements in the fields of astronomy, physics, anatomy, biology, and chemistry.
The Scientific Method
The scientific method is a systematic and logical approach to the acquisition of knowledge (see Figure below). It uses specific techniques to observe and investigate natural phenomena. The scientific method differs from other methods of inquiry in that scientists seek to let reality speak for itself rather than approaching inquiry with any preconceived biases towards one explanation or another. The steps of the scientific method are: (1) formulating a question, (2) making a hypothesis, (3) testing the hypothesis through experimentation, (4) analyzing results, and (5) developing theories or revising the hypothesis.
The steps of the scientific method are easily represented using a flowchart.
Formulating a Question
The formulation of a question represents the first step in scientific inquiry. The type of question can be very specific or more general. Questions are often based on observations. For example, suppose that you observe that a lamp does not light up when you turn on the switch. The natural question is to ask why the lamp does not work. This in turn would lead to an investigation of the possible reasons why the lamp is not working. However, the process begins with a question that needs to be answered.
Making a Hypothesis
A hypothesis is a testable conjecture that proposes an answer to the question. A hypothesis for the nonfunctioning lamp could be that the light bulb is burned out. In order to be a valid hypothesis, it must be possible to test it.
Testing the Hypothesis and Analyzing Results
The light bulb could be easily removed and replaced with another one. If the new light bulb works, then the original hypothesis is confirmed. However, if the lamp still does not work even when the light bulb has been replaced, the hypothesis is now in question. Further experiments with more light bulbs could be done. Eventually, if the lamp continues not to work, the original hypothesis must be discarded. At this point, the scientist may decide to either make a slight change in the hypothesis or abandon the experiment entirely. Perhaps the change could be that there is a problem with the switch for the lamp that is preventing it from working. A new set of experiments could be performed to determine if the original switch was responsible for the lamp not working.
The lamp example oversimplifies the usual process in a real scientific experiment. In most experiments, multiple experimental groups are created in order to test the effect of one variable on another. For example, suppose that you wanted to know how elevated air temperature affects the germination rate of a certain type of bean seed. You would set up multiple pots planted in identical fashion with the same bean seeds. You would establish experimental constants such as the amount of water and the amount of light that each planting would receive. The independent variable in an experiment is the variable that is changed during an experiment. In this case, the temperature is the independent variable. You would figure out a way to place each of the experimental groups at a different elevated temperature. One planting would be left at room temperature. This is called the control group. A control group is a group that experiences the same conditions as the experimental groups with the exception of the variable that is being tested. The bean plantings would be observed at regular intervals, perhaps every 12 hours. Data would be collected as to how many bean seeds germinated in each planting and when germination took place. The dependent variable in an experiment is the variable that is observed during an experiment. In this experiment, germination of the bean seeds is the dependent variable.
In order to be confident about the results of an experiment, it needs to be repeatable. Professional scientists normally repeat experiments many times before they make their findings known to other scientists or to the public.
If many experiments are performed and each and every one supports the hypothesis, it may be that the hypothesis can be accepted. A theory is an explanation that has been repeatedly tested and confirmed by multiple researchers and has gained wide acceptance. The term theory is one that is often misunderstood by people in the general population who are unfamiliar with the scientific method. Though a scientist may state that a theory cannot be proven correct, he or she is certainly not saying that it is in doubt. A scientific theory has generally been confirmed over and over and over again, although small details within a theory may be adjusted from time to time as new discoveries are made. In a later chapter you will learn about atomic theory and how it has changed over the last few centuries. While the existence of atoms has not been in question for some time, new details about how the atom functions have resulted in many updates and alterations of the essential theory.
A scientific law is a statement that summarizes the results of many observations and experiments and to which there are no known exceptions. A familiar scientific law is the law of gravity. The force of attraction between two objects is dependent in a very specific way on the masses of those objects and on the distance between them. The law of gravity has been tested and proven countless times. Scientific laws often have a mathematical basis, though that is not necessarily a requirement.
Today’s scientists rarely work alone. Rather, most scientists collaborate with one another in various settings as part of a group effort. The majority of research scientists work either for a company, such as the DuPont Chemical Company, or for one of many universities, such as the California Institute of Technology. Working as part of a group has many advantages. Most scientific problems are so complex and time-consuming that one person could not hope to address all of the issues by himself or herself. Instead, different members of a research group are each tasked with a particular small aspect of a larger research problem. Collaboration between members of the group is frequent. This occurs informally in the laboratory on an everyday basis. Research groups also typically have regular meetings where one or more members of the group may give a presentation to the others on the status of the research that they are doing. Progress normally occurs in small steps rather than grand, sweeping discoveries, and that progress is helped along by the teamwork that comes from working as part of a group.
Modern scientific research is usually expensive. Lab equipment, chemicals, research space, and the upkeep of technical instrumentation all cost money. Research groups need to raise money in order to continue their work. For research done at universities, much of that money comes from government sources, such as the National Science Foundation or the National Institute of Health. Private companies can fund their own research, but they may seek outside funding as well. Scientists write grant proposals explaining the goals and projected costs of their research, and funding agencies make decisions about which research projects they would like to fund. The long-term viability of most research labs depends on the ability to get and maintain funding.
Suppose that your research is a success. What now? Scientists communicate their results to one another and to the public at large in several ways. One is to publish their research findings in publications called scientific journals. There are many hundreds of scientific journals covering every imaginable field of science. A few of the major chemistry journals include the “Journal of the American Chemical Society,” the “Journal of Physical Chemistry,” and “Inorganic Chemistry.” Some journals have a very narrow scope while others publish articles from many different scientific disciplines and appeal to a wider audience. Examples of the latter include the journals “Science” and “Nature.” Journal articles are often very complex and detailed. They must be accurate, since the research field as a whole uses these journal articles as a way to make scientific progress. Therefore, journal articles are only published after having been extensively reviewed by other professional scientists in the same field. Reviewers have the power to make suggestions about the research or possibly question the validity of the author’s conclusions. Only when the reviewers are satisfied that the research is correct will the journal publish the article. This peer-review process allows scientists to trust the research findings that they read about in journals.
Scientists also communicate with one another by presenting their findings at international conferences. Some scientists are chosen to give lectures at conferences, typically about research that has already been published. Many other scientists at the same conference will present their work at poster sessions (see Figure below). These poster sessions are more informal and may often represent research that is still in progress.
Scientists at a poster session
- The Renaissance, which took place in Europe between the 14th and 17th centuries, was a time of great change in thought and culture. Along with many other changes, science began to follow a more systematic approach based on careful observation and experimentation.
- The steps of the scientific method are to formulate a question, make a hypothesis, perform experiments, analyze the results, and develop theories.
- Professional scientists collaborate with one another by working in research groups and present their results in scientific journals and at international conferences.
Lesson Review Questions
- What were some of the scientific contributions of da Vinci and Copernicus?
- What is a key requirement for a hypothesis to be a valid part of the scientific method?
- Which of the following is not a part of the scientific method?
- What is the next step if a particular experiment is inconsistent with the hypothesis?
- Why do scientists repeat experiments?
- What is the difference between the independent variable and the dependent variable in an experiment?
- What makes a theory different from a hypothesis?
- What is a scientific journal and what is meant by the term “peer review”?
- A student decides to test the effect of added salt on the boiling point of water. He collects the following data (Table below):
Amount of added salt (g)
Boiling Temperature (°C)
- What is the independent variable?
- What is the dependent variable?
- What is the purpose of the first experiment, when no salt was added to the water?
- What needs to be kept constant during the experiment in order for the results to be valid?
Further Reading / Supplemental Links
Points to Consider
Chemistry is the study of matter and the changes that it undergoes. Before beginning to examine those changes, it is important to be able to classify matter according to certain common characteristics and be able to recognize when a chemical change is occurring.
- What properties of matter allow it to be classified?
- What clues allow a chemist to recognize a chemical reaction?