Posts Tagged Chemistry Schools
The "solvent" in air is nitrogen, a diatomic element that accounts for 78% of Earth's atmosphere. Oxygen, also diatomic, constitutes an additional 21%. Argon, which like all noble gases is monatomic, ranks a distant third, with 0.93%. The remaining 0.07% is made up of traces of other noble gases; the two compounds mentioned, carbon dioxide and water (in vapor form); and, high in the atmosphere, the triatomic form of oxygen known as ozone (O 3 ).
The most significant solid solutions are alloys
December 9, 2009
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In dissolving the salt, water molecules surround ions that make up the salt, holding them in place through the electrical attraction of opposite charges. Due to the differences in electronegativity that give the water molecule its high polarity, the hydrogen atoms are more positively charged, and thus these attract the negatively charged chlorine ion. Similarly, the negatively charged oxygen end of the water molecule attracts the positively charged sodium ion. As a result, the salt is "surroun
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The hydrocarbon end (R-) is said to be lipophilic, or "oil-loving"; on the other hand, the carboxylate end (-COO-) is hydrophilic, or "water-loving." As a result, soap can dissolve in water, but can also clean greasy stains. When soap is mixed with water, it does not form a true solution, due to the presence of the hydrocarbons, which attract one another to form spherical aggregates called micelles. The lipophilic "tails" of the hydrocarbons are turned toward the interior of the micelle, while
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Everyone has had the experience of eating spicy foods and then trying to cool down the mouth with cold water—and just about everyone has discovered that this does not work. Though a great deal of milk is composed of water, it also contains tiny droplets of fats and proteins that join with the oils in spicy substances, thus cooling down the mouth.
CROSSING THE OIL / WATER BARRIER
The active ingredient in a dry-cleaning chemical usually has nonpolar molecules, because the toughest stains ar
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DILUTION AND CONCENTRATION.
Another useful set of qualitative terms for solutions also relates to the relative amount of solute that has been dissolved. But whereas saturation is an absolute condition at a certain temperature (in other words, the solution is definitely saturated at such-and-such a temperature), concentration and dilution are much more relative terms.
When a solution contains a relatively small amount of solute, it is said to be dilute; on the other hand, a solution with a re
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OTHER QUANTITATIVE TERMS.
Another quantitative means of describing a solution is in terms of mass percent: the mass of the solute divided by the mass of the solution, and multiplied by 100%. If there are 25 g of solute in a solution of 200 g, for instance, 25 would be divided by 200 and multiplied by 100% to yield a 12.5% figure of solution composition.
Molarity also provides a quantitative means of showing the concentration of solute to solution. Whereas mass percent is, as its name indicat
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Download Solutions of Nature Science Ability Practice Test of Simak UI 2010
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In a homogeneous mixture, by contrast, there is no difference between one area of the mixture and another. If coffee has been brewed properly, and there are no grounds at the bottom of the pot, it is homogeneous. If sweetener is added to tea while it is hot, it too should yi
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CONCEPT
Certainly there is a special place in chemistry for solutions in which water—"the universal solvent"—provides the solvent medium. Coffee, tea, soft drinks, and even water itself (since it seldom appears in pure form) are solutions, but the meaning of the term is not limited to solutions involving water. Indeed, solutions do not have to be liquid; they can be gaseous or solid as well. One of the most important solutions in the world, in fact, is the air we breathe, a combination
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