Models are an important part of chemistry because they show how a scientific theory can be changed over time due to new evidence. For example Greek philosopher Democritus proposed the existence of atoms, but his argument lacked experimental support. Because his theory was not based on scientific method, it was dismissed until Dalton used experimental methods to change Democritus’s idea into scientific theory. The most prominent example of how a scientific model can change over time is the atom. John Dalton an English chemist was the first person to propose an atomic theory and back it up with experimental evidence. He decided to study the ratios of elements when they combine in chemical reactions. He observed this and was able to come up …show more content…
He kept the gasses in glass tubes and at the end of each side of the tube, laid an electrode. The electrodes were connected to electricity, and on one side the electrode was charged positively, and on the other side it had a negative charge. He found that it formed a glowing beam, which he called a cathode ray. He knew from previous knowledge that opposite charges attract and like charges repel, so he hypothesized that a cathode ray is a flood of small negatively charged particles moving at a high speed, because the rays flowed in the direction of the positive electrode, which meant that the rays must be negative. To test his findings, he used an experiment where he measured the ratio of charge of an electron to its mass and he discovered that the ratio is constant, and that this ratio did not depend on the kind of gas nor the type of metal used for the electrodes. Then shortly after, U.S physicist Robert A. Millikan conducted an experiment where he had to find the amount of charge carried by an electron. He used the value he found and the charge-to-mass ratio of an electron that Thomson had discovered, to determine the mass of an electron. He was extremely close to the fact that is accepted today, which is that the electron carries one unit of negative charge, and its mass is 1/1840 the mass of a …show more content…
Rutherford and his coworkers experiment consisted of shooting a narrow beam of alpha particles at a sheet of gold foil, which was supposed to allow the particles to pass easily through. The majority of the particles passed through with ease, except for a select few that bounced off straight back at the source. This caused Rutherford to conclude that an atom is mostly empty space because of the lack of deflection and he was also able to conclude that all of the positive charge of an atom and nearly all its mass is concentrated in the core of the atom, which he called the nucleus. He came to this conclusion because it was the only way to account for the particles that were actually being deflected, which required a certain amount of positive
In 1895, Professor Wilhelm C. Roentgen, a German physicist, was working with a cathode ray tube, much like our fluorescent light bulb. The tube consisted of positive and negative electrodes encapsulated in a glass envelope. On November 8, 1895, Roentgen was conducting experiments in his lab on the effects of cathode rays. He evacuated all the air from the tube and passed a high electric voltage through it after filling it with a special gas. When he did this, the tube began to give off a fluorescent glow. Roentgen then shielded the tube with heavy black paper and discovered a green colored fluorescent light could be seen coming from a screen located a few feet away from the tube.
Physicist in the 1900 first started to consider the structure of atoms. The recent discovery of J. J. Thomson of the negatively charged electron implied that a neutral atom must also contain an opposite positive charge. In 1903 Thomson had suggested that the atom was a sphere of uniform positive electrification , with electrons scattered across it like plum in an pudding. (Later known as the Plum Pudding Model)
physics. The work of Ernest Rutherford, H. G. J. Moseley, and Niels Bohr on atomic
Further research is conducted to test the theory and the model. As advances in technology occur, more information can be obtained and so the theories and models can then be altered. If the model or theory seems to hold true in numerous areas of science, a scientific law is formed. These laws provide a greater level of understanding and explain why many things happen. An example of a law is Sir Isaac Newton’s law of Inertia.
This includes the introduction of the heliocentric model and the debate about pluto being a planet, that ended up changing view points on many topics.
Carl G. Hempel was of the most influential proponents of what is now regarded as the classic view of explanation in science. In his work, Philosophy of Natural Science, he created the deductive-nomological model which is the following account of scientific explanation, where an explanation is set out as a formalized argument. This is the principle format for works such as Aristotle’s Physica, Ptolemy’s Almagest, Newton’s Principia and Opticks, Franklin’s Electricity, Lavoisie’s Chemistry, and Lyell’s Geology. Thomas Kuhn calls these achievements Paradigms. Through these paradigms normal science developed. In Kuhn’s book, The Structure of Scientific Revolutions, he argues that normal science in a way hinders the development of new phenomenon. He says that there must be a change in a paradigm to create a scientific revolution. Throughout this essay I will explain what Hempel’s model consists of and how it relates to Kuhn’s view.
Scientific theory by definition seeks to explain observed phenomena by stating the causal reasons that led to the event. The central component of the theory must adhere to the principles of
he found the number of alpha particles emitted per second by a gram of radium.
Theory is an attempt to explain the unexplained, to give title to the untitled and to give reason to the unreasonable. It is a combination of existing knowledge and newly acquired knowledge that allows us to make assumptions in order to realize reasonably foreseeable outcomes. It is only in the realms of science, physics and mathematics that the repeated application
To begin, theories change in different ways. For example, theories change if facts are found to be incorrect, maybe something was not thought out enough, and if any of the trials fail. In 460-370 B.C some scientists were to believe that atoms were completely solid because atoms were so small they couldn’t split. In 500 B.C Leucippus and Democritus proposed that all matter is composed of tiny particles called atoms that can't be split into smaller pieces. In 1821 Michael Faraday discovered electricity by carrying a wire with an electric current to a magnetic pole and then the wire rotated. Also, in 1930-2006 scientists decided that Pluto was not a planet but was a dwarf planet and the reason why Pluto is no longer a planet is because astronomers
The 1800’s was a time of development in science. New and what seemed like crazy ideas were surfacing. These ideas were more easily accepted than in past years. There were new theories such as the Cell Theory by Mathias Schleiden and Theodor Schwann in 1838 (Farah 626) and the Atomic Theory by John Dalton (Farah 628).A little over a decade after the Cell Theory was proposed, Louis Pasteur discovered bacteria in 1850 (Farah 627).
According to the de Broglie relation and Bragg's law, a beam of 54 eV had a wavelength of 0.167 nm. The experimental outcome was 0.165 nm via the grating equation, which closely matched the predictions. Davisson and Germer's accidental discovery of the diffraction of electrons was the first direct evidence confirming de Broglie's hypothesis that particles can have wave properties as well.
Throughout Thomson’s life he made many contributions to science. These include discoveries in thermodynamics and the age of the Earth, as well as innovating the Transatlantic Cable and inventing a tide meter. After exploring thermodynamics for some time, he developed the second law of thermodynamics. This law states that there cannot be a reaction that is completely efficient; a portion of the energy is lost to heat in each reaction. It also says that heat flows to areas that...
A scientific theory is an explanation that is well- substantiated explanation in regards to some aspect of the natural world that is attained through scientific method and is tested numerous times and usually confirmed through vigorous observation and experimentation. The term theory can be seen as a collection of laws which allow you to show some kind of phenomenon. The strength of a scientific theory associated with the diversity of phenomena can explain its elegance and simplicity. However when new evidence is gathered a scientific theory can be changed or even rejected if it does not fit the new findings, in such cases a more accurate theory is formed. Scientific theories are used to gain further
Dalton’s idea is that all things are made of small bits of matter, these bits of matter where too small to be seen even with a microscope. Scientists began to think these small bits of matter were responsible for chemical changes. They thought that when these bits of matter combined, a chemical change took place. Dalton assumed that there was a special pattern in the elements and was partly responsible for the periodic table. Dalton in 1787 started to keep a journal.