Summary:
A description of the life of chemist and physicist John Dalton (1766-1844). Dalton is known as the father of chemistry, as his works provide the foundation for our understanding of chemistry. He is also known for his contributions to modern-day atomic theory.
John Dalton was a great chemist and physicist. He made many important contributions to science that are still used today. Because of his discoveries, Dalton is known as the father of chemistry and the founder of our modern day atomic theory.
John Dalton was born on September 6, 1766 in Eaglesfield, England. His father, Joseph Dalton, was a weaver. Dalton also had two siblings, a brother and a sister. He and his family were Quakers and they did not have much money, but Dalton still received a good education at a nearby Quaker school. He was a very smart student and did very well at math. His teacher, John Fletcher, was a very good teacher and gave John a thirst for knowledge. John also had a mentor, Elihu Robinson, who provided him with understanding in math and science, meteorology especially. When Dalton was only twelve, he opened a school in Cumberland and taught there. However, because of the poor salary, he was forced to return home to work for his uncle.
In 1781, John moved to Kendall. In Kendall, with the help of his brother, he ran a school that offered a variety of different subjects, including twenty-one math and science classes. After twelve years of teaching at this school, he became a teacher at New College in Manchester. He stayed here until 1800 when he resigned to become the secretary of the Manchester Literary and Philosophical Society. In 1817, he became the president of this Society.
In 1787, he began recording many meteorological observations in a journal. Dalton continued this for 57 years and made over 200,000 observations and measurements on the weather in the area in which he lived. He had an interest in meteorology and this led him to study a great deal about this subject. Dalton made many conclusions about trade winds involving the Earth's rotation and temperature, but unbeknownst to him, George Hadley had already made these conclusions in 1735. He studied other topics as well including the formation of clouds and the concept of dew point. Dalton was the first to verify the theory that rain is caused by a decrease in temperature, not a change in atmospheric pressure. He published his first work, Meteorological Observations and Essays in 1793, which included his findings on these subjects. He did not attract much attention for these works.
In the following year, he presented his paper on color blindness to the Literary and Philosophical Society. Dalton and his brother were both colorblind. They did not know it until one year, for their mother's birthday, John bought her some stockings. When his mother received them, she was surprised and asked why John had bought her scarlet stockings. John had thought they were blue and turned to his brother to verify the color. Their mother asked another woman and found they were actually red. Dalton became very interested in colorblindness after this incident and published a paper called "Extraordinary Facts Relating to the Vision of Colors." He hypothesized that the cause of colorblindness was a discoloration of a liquid within the eye. He requested an autopsy be done when he died to see if his hypothesis was correct. Dalton's theory proved to be incorrect, but because of his comprehensive research, Daltonism became a common term for color blindness.
John Dalton conducted research on these and many other topics, but he is most well known for his discoveries relating to the atomic theory. During the time Dalton lived, scientists never understood the concept of states of matter because they did not comprehend heat. They did not realize that heat was a form of energy; they believed that heat was a substance called caloric that could transfer from one object to another. This explanation was called the caloric theory. Dalton used this theory to propose that a molecule of a gas is surrounded by caloric that repels other molecules. As the gas increases in temperature, the repulsive force gets stronger and the gas exerts a greater pressure on the walls of its container. Although this explanation is wrong, his works with this later helped him to come up with Dalton's law.
As one author put it, "Dalton's law states that in a mixture of different gases, such as air, the sum of the partial pressures of all the gases equals the total pressure of the mixture." The partial pressure of a gas is the pressure that gas would exert if only it were present. For example, air is made up of mainly nitrogen and oxygen. Nitrogen makes up 78 percent of air pressure in Earth's atmosphere and oxygen for 21 percent. Along with small quantities of other substances, these add up to the total air pressure in the atmosphere. This work with gases started Dalton thinking about substances on a level of particles that are too small to be seen, atoms.
Dalton contributed many things to the view we have on atoms today. He found clear and credible proof that atoms actually exist. He also found some of the first clues on the nature of atomic particles. Dalton's ideas about atoms were very different compared to that of the Greeks who were the first to propose the idea. His ideas stated that the characteristics of an atom determine the chemical and physical properties of a substance, no matter what the substance's form. For example, carbon atoms can be in the form of coal or diamonds. The old Greek theory would have seen these as being two different substances, not one. Dalton's theory said the atoms in these two substances would be very similar because they both are made up of the same element.
Dalton also conducted research on the way elements combine. He studied how two elements can combine in more than one way and how different quantities of a certain element, combined with another, can form different compounds. For example, one carbon atom and one oxygen atom combine to form carbon dioxide, while if one carbon atom combines with two oxygen atoms the result is carbon dioxide. Dalton concluded that when atoms of pure elements join in fixed proportions, they form units that today, are called molecules. He said when a certain number of atoms of a substance combine with the same number of atoms of another substance the resulting compound contains the same number of molecules as in the original substance. For example, ten sodium molecules combine with ten chloride molecules to form ten sodium chloride molecules.
Dalton was also the first person to classify elements according to their atomic mass. He gave water a formula related to HO and randomly gave hydrogen the atomic weight of one. By using this number, he could then calculate the atomic weight of oxygen. He used this same process with other compounds and was therefore able to create a table of all the known elements and their atomic weights. Although many of his values were incorrect, he had the right idea. Dmitry Mendeleyev later used Dalton's discoveries to arrange the periodic table that was based on atomic number, not mass.
In 1808, Dalton published his book "A New System of Chemical Philosophy." In this book, he made two statements. These statements, along with his other observations, form Dalton's atomic theory of matter. This theory is based on four postulates: Each element is composed of small particles called atoms, all atoms of a given element are identical and differ from those of any other elements, atoms are neither created nor destroyed in any chemical reaction, and a given compound always has the same numbers and kinds of atoms. These four postulates have some small exceptions, but are still the basis of modern day atomic theory.
John Dalton died on July 27, 1844 of a stroke, but not before recording the weather for that day. Dalton lived a very productive life. He made many contributions to the world of chemistry and physics and his works are the basis and foundation for our understanding of chemistry. His numerous discoveries and theories prove that he deserves the name, the father of chemistry.
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