This may occur at any number of stages in a manufacturing process, including the very critical steps involved in removing toxic, odiferous, or otherwise undesirable by-products from a waste stream. But even in the research lab, a considerable amount of effort is often devoted to separating the desired substance from the many components of a reaction mixture, or in separating a component from a complex mixture for example, a drug metabolite from a urine sample , prior to measuring the amount present.
Distillation - separation of liquids having different boiling points. This ancient technique believed to have originated with Arabic alchemists in BCE , is still one of the most widely employed operations both in the laboratory and in industrial processes such as oil refining. Solvent extraction - separation of substances based on their differing solubilities. A common laboratory tool for isolating substances from plants and chemical reaction mixtures.
Practical uses include processing of radioactive wastes and decaffeination of coffee beans. The separatory funnel shown here is the simplest apparatus for liquid-liquid extraction; for solid-liquid extraction, the Soxhlet apparatus is commonly used.
Chromatography - This extremely versatile method depends on the tendency of different kinds of molecules to adsorb attach to different surfaces as they travel along a "column" of the adsorbent material. Just as the progress of people walking through a shopping mall depends on how long they spend looking in the windows they pass, those molecules that adsorb more strongly to a material will emerge from the chromatography column more slowly than molecules that are not so strongly adsorbed.
Gel electrophoresis - a powerful method for separating and "fingerprinting" macromolecules such as nucleic acids or proteins on the basis of physical properties such as size and electric charge. The answer is that all depend on analytical techniques — measurements of the nature or quantity "assays" of some substance of interest, sometimes at very low concentrations.
A large amount of research is devoted to finding more accurate and convenient means of making such measurements. Many of these involve sophisticated instruments; among the most widely used are the following:. Spectrophotometers that examine the ways that light of various wavelengths is absorbed, emitted, or altered by atomic and molecular species. Mass spectrometers that break up molecules into fragments that can be characterized by electrical methods. Instruments NMR spectrometers that analyze the action of radio waves and magnetic fields on atomic nuclei in order to examine the nature of the chemical bonds attached to a particular kind of atom.
Today, using X-ray fluorescence spectrometry, two chemists can perform the same type of analysis on 7, samples per year. Materials science attempts to relate the physical properties and performance of engineering materials to their underlying chemical structure with the aim of developing improved materials for various applications.
Polymer chemistry - developing polymeric "plastic" materials for industrial uses. Connecting individual polymer molecules by cross-links red increases the strength of the material. Thus ordinary polyethylene is a fairly soft material with a low melting point, but the cross-linked form is more rigid and resistent to heat. Organic semiconductors offer a number of potential advantages over conventional metalloid-based devices. Fullerenes, nanotubes, and nanowires - Fullerenes were first identified in as products of experiments in which graphite was vaporized using a laser, work for which R.
Curl, Jr. Smally, and H. Kroto shared the Nobel Prize in Chemistry. Fullerene research is expected to lead to new materials, lubricants, coatings, catalysts, electro-optical devices, and medical applications. Nanodevice chemistry — constructing molecular-scale assemblies for specific tasks such as computing, producing motions, etc. Biosensors and biochips - the surfaces of metals and semiconductors "decorated" with biopolymers can serve as extremely sensitive detectors of biological substances and infectious agents.
This field covers a wide range of studies ranging from fundamental studies on the chemistry of gene expression and enzyme-substrate interactions to drug design. Much of the activity in this area is directed to efforts in drug discovery. Drug screening began as a largely scattershot approach in which a pathogen or a cancer cell line was screened against hundreds or thousands of candidate substance in the hope of finding a few "leads" that might result in a useful therapy.
This field is now highly automated and usually involves combinatorial chemistry see below combined with innovative separation and assay methods. Drug design looks at interactions between enzymes and possible inhibitors.
Computer-modeling is an essential tool in this work. Proteomics - This huge field focuses on the relations between structure and function of proteins— of which there are about , different kinds in humans. Proteomics is related to genetics in that the DNA sequences in genes get decoded into proteins which eventually define and regulate a particular organism. Chemical genomics explores the chain of events in which signaling molecules regulate gene expression.
In its most general sense, this word refers to any reaction that leads to the formation of a particular molecule. It is both one of the oldest areas of chemistry and one of the most actively pursued. Some of the major threads are.
Combinatorial chemistry refers to a group of largely-automated techniques for generating tiny quantities of huge numbers of different molecules "libraries" and then picking out those having certain desired properties. Although it is a major drug discovery technique, it also has many other applications. Green chemistry - synthetic methods that focus on reducing or eliminating the use or release of toxic or non-biodegradable chemicals or byproducts. Process chemistry bridges the gap between chemical synthesis and chemical engineering by adapting synthetic routes to the efficient, safe, and environmentally-responsible methods for large-scale synthesis.
You have just covered all of Chemistry, condensed into one quick and painless lesson— the world's shortest Chemistry course! Yes, we left out a lot of the details, the most important of which will take you a few months of happy discovery to pick up.
Chem1 Virtual Textbook. Learning Objectives Distinguish beween chemistry and physics ; Suggest ways in which the fields of engineering, economics, and geology relate to Chemistry; Define the following terms, and classify them as primarily microscopic or macroscopic concepts: element, atom, compound, molecule, formula, structure. The two underlying concepts that govern chemical change are energetics and dynamics.
What aspects of chemical change does each of these areas describe? So just what is chemistry? Thus we can view chemistry from multiple standpoints ranging from the theoretical to the eminently practical: Mainly theoretical Mainly practical Why do particular combinations of atoms hold together, but not others?
What are the properties of a certain compound? How can I predict the shape of a molecule? How can I prepare a certain compound? Why are some reactions slow, while others occur rapidly? Does a certain reaction proceed to completion?
Is a certain reaction possible? How can I determine the composition of an unknown substance? Boiling it down to the basics At the most fundamental level, chemistry can be organized along the lines shown here.
Dynamics refers to the details of that rearrangements of atoms that occur during chemical change, and that strongly affect the rate at which change occurs. Energetics refers to the thermodynamics of chemical change, related to the uptake or release of heat. This aspect of chemistry controls the direction in which change occurs, and the mixture of substances that are produced as a result. Composition and structure define the substances that are produced because of a chemical change.
Structure specifically refers to the relative arrangements of the atoms in space. The extent to which a given structure can persist is determined by energetics and dynamics. Synthesis refers to formation of new and usually more complex substances from simpler ones, but in the present context we use it in the more general sense to denote the operations required to bring about chemical change and to isolate the desired products. But if you need a single-sentence "definition" of Chemistry, this one wraps it up pretty well: Chemistry is the study of substances ; their properties, structure, and the changes they undergo.
Micro-macro: the forest or the trees Chemistry, like all the natural sciences, begins with the direct observation of nature — in this case, of matter. Chemical composition Mixture or "pure substance"?
Elements and compounds It has been known for at least a thousand years that some substances can be broken down by heating or chemical treatment into "simpler" ones, but there is always a limit; we eventually get substances known as elements that cannot be reduced to any simpler forms by ordinary chemical or physical means.
Elements and atoms The definition of an element given above is an operational one; a certain result or in this case, a non-result! He described in painful detail the composition of the bars and the heavy shackles on the pad locks. Plus, did you know that meditation can change your brain composition — just like exercise can change your body? He approaches the composition of a painting rather as a theatrical director might set the scene of a play.
He was the most distinguished representative of the English school of composition , and was knighted in When he plays a sonata it is as if the composition rose from the dead and stood transfigured before you.
Of writing he knew little and the art of composition appeared very difficult. The countess-dowager was not very adroit at spelling and composition , whether French or English, as you observe. Tausig, in my opinion, did possess exceptional genius in composition , though he left but few works behind him to attest it.
Because it is thick and has relatively low density, continental crust rises higher on the mantle than oceanic crust, which sinks into the mantle to form basins.
The lithosphere is the outermost mechanical layer, which behaves as a brittle, rigid solid. The lithosphere is about kilometers thick. The definition of the lithosphere is based on how earth materials behave, so it includes the crust and the uppermost mantle, which are both brittle.
Since it is rigid and brittle, when stresses act on the lithosphere, it breaks. This is what we experience as an earthquake. The two most important things about the mantle are: 1 it is made of solid rock, and 2 it is hot.
Scientists know that the mantle is made of rock based on evidence from seismic waves, heat flow, and meteorites. The properties fit the ultramafic rock peridotite, which is made of the iron- and magnesium-rich silicate minerals. Scientists know that the mantle is extremely hot because of the heat flowing outward from it and because of its physical properties. Heat flows in two different ways within the Earth: conduction and convection. Conduction is defined as the heat transfer that occurs through rapid collisions of atoms, which can only happen if the material is solid.
Heat flows from warmer to cooler places until all are the same temperature. The mantle is hot mostly because of heat conducted from the core. Convection is the process of a material that can move and flow may develop convection currents. Convection in the mantle is the same as convection in a pot of water on a stove. As the core heats the bottom layer of mantle material, particles move more rapidly, decreasing its density and causing it to rise.
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