Properties of Solids
Michael Springborg heads up of the three groups in Physical Chemistry at the University of Saarland where the main activities concentrate on teaching and research. Wiley Series in Theoretical Chemistry. Undetected location. NO YES. Home Subjects Chemistry Physical Chemistry.
Selected type: Hardcover. Italian dressing is an example of a heterogeneous mixture Figure 1. Its composition can vary because it may be prepared from varying amounts of oil, vinegar, and herbs. It is not the same from point to point throughout the mixture—one drop may be mostly vinegar, whereas a different drop may be mostly oil or herbs because the oil and vinegar separate and the herbs settle. Other examples of heterogeneous mixtures are chocolate chip cookies we can see the separate bits of chocolate, nuts, and cookie dough and granite we can see the quartz, mica, feldspar, and more.
A homogeneous mixture , also called a solution , exhibits a uniform composition and appears visually the same throughout. An example of a solution is a sports drink, consisting of water, sugar, coloring, flavoring, and electrolytes mixed together uniformly Figure 1. Each drop of a sports drink tastes the same because each drop contains the same amounts of water, sugar, and other components. Note that the composition of a sports drink can vary—it could be made with somewhat more or less sugar, flavoring, or other components, and still be a sports drink.
Other examples of homogeneous mixtures include air, maple syrup, gasoline, and a solution of salt in water. Although there are just over elements, tens of millions of chemical compounds result from different combinations of these elements. Each compound has a specific composition and possesses definite chemical and physical properties that distinguish it from all other compounds. And, of course, there are innumerable ways to combine elements and compounds to form different mixtures.
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A summary of how to distinguish between the various major classifications of matter is shown in Figure 1. Oxygen constitutes nearly one-half and silicon about one-quarter of the total quantity of these elements. A majority of elements on earth are found in chemical combinations with other elements; about one-quarter of the elements are also found in the free state. An atom is the smallest particle of an element that has the properties of that element and can enter into a chemical combination.
Consider the element gold, for example. Imagine cutting a gold nugget in half, then cutting one of the halves in half, and repeating this process until a piece of gold remained that was so small that it could not be cut in half regardless of how tiny your knife may be. This atom would no longer be gold if it were divided any further.
The first suggestion that matter is composed of atoms is attributed to the Greek philosophers Leucippus and Democritus, who developed their ideas in the 5th century BCE. However, it was not until the early nineteenth century that John Dalton — , a British schoolteacher with a keen interest in science, supported this hypothesis with quantitative measurements.
Since that time, repeated experiments have confirmed many aspects of this hypothesis, and it has become one of the central theories of chemistry. An atom is so small that its size is difficult to imagine. Although the cross-section of one strand is almost impossible to see without a microscope, it is huge on an atomic scale.
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A single carbon atom in the web has a diameter of about 0. Figure 1. An atom is so light that its mass is also difficult to imagine. It is rare to find collections of individual atoms. Only a few elements, such as the gases helium, neon, and argon, consist of a collection of individual atoms that move about independently of one another. Other elements, such as the gases hydrogen, nitrogen, oxygen, and chlorine, are composed of units that consist of pairs of atoms Figure 1.
One form of the element phosphorus consists of units composed of four phosphorus atoms. The element sulfur exists in various forms, one of which consists of units composed of eight sulfur atoms. These units are called molecules. A molecule consists of two or more atoms joined by strong forces called chemical bonds.ipdwew0030atl2.public.registeredsite.com/102306-the-best-mobile.php
NMR studies of electronic properties of solids - Scholarpedia
The atoms in a molecule move around as a unit, much like the cans of soda in a six-pack or a bunch of keys joined together on a single key ring. A molecule may consist of two or more identical atoms, as in the molecules found in the elements hydrogen, oxygen, and sulfur, or it may consist of two or more different atoms, as in the molecules found in water. Each water molecule is a unit that contains two hydrogen atoms and one oxygen atom. Each glucose molecule is a unit that contains 6 carbon atoms, 12 hydrogen atoms, and 6 oxygen atoms.
Like atoms, molecules are incredibly small and light. If an ordinary glass of water were enlarged to the size of the earth, the water molecules inside it would be about the size of golf balls.
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- 1. Introduction.
Water consists of the elements hydrogen and oxygen combined in a 2 to 1 ratio. Water can be broken down into hydrogen and oxygen gases by the addition of energy. One way to do this is with a battery or power supply, as shown in Figure 1. The breakdown of water involves a rearrangement of the atoms in water molecules into different molecules, each composed of two hydrogen atoms and two oxygen atoms, respectively.
They are generally incompressible, meaning they cannot be compressed into smaller shapes. Because of the repeating geometric structure of the crystal, all the bonds between the particles have equal strength. This means that a crystalline solid will have a distinct melting point, because applying heat will break all the bonds at the same time.
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This means that properties such as refractive index how much light bends when passing through the substance , conductivity how well it conducts electricity and tensile strength the force required to break it apart will vary depending on the direction from which a force is applied. There are four types of crystalline solids: ionic solids, molecular solids, network covalent solids and metallic solids. Because of the strong attraction between opposite charges, it takes a lot of energy to overcome ionic bonds.
This means that ionic compounds have very high melting points, often between and 1, degrees Celsius to 1, degrees Fahrenheit. While the crystals themselves are hard, brittle and nonconductive, most ionic compounds can be dissolved in water, forming a solution of free ions that will conduct electricity. They may be simple binary salts like sodium chloride NaCl , or table salt, where one atom of a metallic element sodium is bonded to one atom of a nonmetallic element chlorine.
Electronic Structure and the Properties of Solids: The Physics of the Chemical Bond
Because covalent bonding involves sharing electrons rather than outright transfer of those particles, the shared electrons may spend more time in the electron cloud of the larger atom, causing weak or shifting polarity. This electrostatic attraction between the two poles dipoles is much weaker than ionic or covalent bonding, so molecular solids tend to be softer than ionic crystals and have lower melting points many will melt at less then C, or F. Most molecular solids are nonpolar. These nonpolar molecular solids will not dissolve in water, but will dissolve in a nonpolar solvent, such as benzene and octane.
Polar molecular solids, such as sugar, dissolve easily in water. Molecular solids are nonconductive. Fullerene "buckyballs" are also molecular solids. In a network solid, there are no individual molecules.