He thought, however, that shape, size, and mass were the only properties differentiating the different types of atomos. According to Democritus, other characteristics, like color and taste, did not reflect properties of the atomos themselves, but rather, resulted from the different ways in which the atomos were combined and connected to one another.
The early Greek philosophers tried to understand the nature of the world through reason and logic, but not through experiment and observation. As a result, they had some very interesting ideas, but they felt no need to justify their ideas based on life experiences. In a lot of ways, you can think of the Greek philosophers as being "all thought and no action. Greek philosophers dismissed Democritus' theory entirely. Sadly, it took over two millennia before the theory of atomos or "atoms," as they are known today was fully appreciated.
Greek philosophers were "all thought and no action" and did not feel the need to test their theories with reality. In contrast, Dalton's efforts were based on experimentation and testing ideas against reality. While it must be assumed that many more scientists, philosophers, and others studied composition of matter after Democritus, a major leap forward in our understanding of the composition of matter took place in the 's with the work of the British scientists John Dalton.
He started teaching school at age twelve, and was primarily known as a teacher. In his twenties, he moved to the growing city of Manchester, where he was able to pursue some scientific studies.
His work in several areas of science brought him a number of honors. Although today's modern "atomic theory" is based on the "atomos" theory; the "Earth, air, fire, and water" theory was the accepted theory for over years. This is because Aristotle proclaimed his support for the "Earth, air, fire and water" model! Dalton's atomic theory John Dalton, an English schoolmaster, proposed the first modern atomic theory. John Dalton was a teacher of mathematics and science by the age of 12; his life was a most remarkable mix of study and inspiration.
In Dalton developed a system of chemical symbols for the known elements and compounds of time. In addition, he proposed that a chemical combination of different elements occurred in simple numerical ratios by weight.
He suggested that all elements are composed of tiny, indestructible particles, he called atoms. Dalton proposed that the atoms of any particular element were all alike and had the same weight. Almost all of the parts of Idea e are addressed once in Chapter 6: Properties of Matter, in the description of the phases of matter.
The different motion of the particles of solids, liquids, and gases is illustrated with an analogy to the movement of children in and after class. The different arrangement and motion of particles of solids and liquids are linked briefly to the definite shape and volume of solids and to the lack of definite shape of liquids.
In addition, the different strength of attraction between particles of diamond, graphite, and soot is connected to the fact that these materials have different properties without stating what the properties are. Idea f: Changes of state—melting, freezing, evaporating, condensing—can be explained in terms of changes in the arrangement, interaction, and motion of atoms and molecules.
The following presentation of Idea b shows which parts of the idea are treated in bold and what alternative vocabulary, if any, is used in brackets : Changes of state—melting, freezing, evaporating, condensing—can be explained in terms of changes in the arrangement, interaction, and motion of atoms and molecules. Explanations of freezing and evaporation at the molecular level are not included.
Building a Case. Like every chapter in Science Insights: Exploring Matter and Energy , the chapters that are related closely to the kinetic molecular theory include numerous features e. For example, some features simply emphasize labeling various phenomena as physical changes e. In other cases, the connection that the material tries to make is contrived and relates only tangentially to the content of the section.
For example, in a section on the properties of gases and their explanation at the molecular level, the text states in Integrating the Sciences that during photosynthesis, plants release oxygen [a gas] into the air and suggests that students see bubbles of oxygen forming on plant leaves in an aquarium p.
Beyond Literacy. Science Insights: Exploring Matter and Energy goes far beyond the key idea that all matter is made up of atoms and includes content that is more appropriate for high school students, well beyond the scope of the science literacy ideas in Benchmarks for Science Literacy American Association for the Advancement of Science, and National Science Education Standards National Research Council, However, when treating the kinetic molecular theory, the material does not go too much beyond the level of sophistication of the key ideas.
Identified errors occur most frequently in drawings and other diagrams. They take the form of representations that are likely to either give rise to or reinforce misconceptions commonly held by students.
Following are physical science examples of the kinds of misleading illustrative materials of most concern to the evaluation teams:. Diagrams and drawings that show atoms or molecules of solids, liquids, and gases in colored backgrounds for example, water molecules inside blue drop shapes and that thereby can initiate or reinforce the misconception that particles are contained in solids, liquids, and gases, in contrast to the correct idea that substances consist of particles with empty space between particles.
Diagrams of solids and occasionally liquids that do not depict the motion of atoms or molecules can give rise to, or reinforce, the misconception that atoms or molecules of solids or liquids are still. Diagrams that show molecules of liquids much farther apart than the molecules of solids are misleading; in most liquids, molecules are only a little farther apart.
Each of the elements is given a name and a one- or two-letter abbreviation. Often this abbreviation is simply the first letter of the element; for example, hydrogen is abbreviated as H, and oxygen as O. Sometimes an element is given a two-letter abbreviation; for example, helium is He. When writing the abbreviation for an element, the first letter is always capitalized and the second letter if there is one is always lowercase.
Atoms: A single unit of an element is called an atom. The atom is the most basic unit of matter , which makes up everything in the world around us. Each atom retains all of the chemical and physical properties of its parent element. At the end of the nineteenth century, scientists would show that atoms were actually made up of smaller, "subatomic" pieces, which smashed the billiard-ball concept of the atom see our Atomic Theory I: The Early Days module.
Compounds: Most of the materials we come into contact with are compounds, substances formed by the chemical combination of two or more atoms of the elements. A single "particle" of a compound is called a molecule. Dalton incorrectly imagined that atoms "hooked" together to form molecules. However, Dalton correctly realized that compounds have precise formulas.
Water, for example, is always made up of two parts hydrogen and one part oxygen. The chemical formula of a compound is written by listing the symbols of the elements together, without any spaces between them.
If a molecule contains more than one atom of an element, a number is subscripted after the symbol to show the number of atoms of that element in the molecule. The formula for water can be written as either H 2 O or HO 2. The idea that compounds have defined chemical formulas was first proposed in the late s by the French chemist Joseph Proust. Proust performed a number of experiments and observed that no matter how he caused different elements to react with oxygen, they always reacted in defined proportions.
For example, two parts of hydrogen always reacts with one part oxygen when forming water; one part mercury always reacts with one part oxygen when forming mercury calx. Dalton used Proust's Law of Definite Proportions in developing his atomic theory. The law also applies to multiples of the fundamental proportion, for example:.
In both of these examples, the ratio of hydrogen to oxygen to water is 2 to 1 to 1. When reactants are present in excess of the fundamental proportions, some reactants will remain unchanged after the chemical reaction has occurred. The story of the development of modern atomic theory is one in which scientists built upon the work of others to produce a more accurate explanation of the world around them.
This process is common in science, and even incorrect theories can contribute to important scientific discoveries. Dalton, Priestley, and others laid the foundation of atomic theory, and many of their hypotheses are still useful.
However, in the decades after their work, other scientists would show that atoms are not solid billiard balls, but complex systems of particles. Thus, they would smash apart a bit of Dalton's atomic theory in an effort to build a more complete view of the world around us. Tracking the development of our understanding of the atomic structure of matter, this module begins with the contributions of ancient Greeks, who proposed that matter is made up of small particles.
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