Mixtures of Matter

Most everyday matter occurs as mixtures— combinations of two or more substances. 

Real-World Reading Link That familiar hiss when you open a soft-drink bottle is the sound of gas escaping. You might have noticed that when you leave the bottle opened, eventually most of the carbon dioxide, will escape. But the soft drink will remain sweet no matter how long you leave the bottle opened. 

You have already read that a pure substance has a uniform and unchanging composition. What happens when two or more subtances are combined A mixture is a combination of two or more pure substances in which each pure substance retains its individual chemical properties. The composition of mixtures is variable, and the number of mixtures that can be created by combining substances is infinite. Although much of the focus of chemistry is the behavior of substances, it is important to remember that most everyday matter occurs as mixtures. Substances tend to mix naturally it is difficult to keep any substance pure. 

A heterogeneous mixture is a mixture that does not blend smoothly throughout and in which the individual substances remain distinct. The salad dressing mixture is an example of a heterogeneous mixture. Its composition is not uniform—the substances have not blended smoothly and remain distinct. In another example, fresh-squeezed orange juice is a heterogeneous mixture of juice and pulp. 

The pulp component floats in the juice component. We can therefore say that the existence of two or more distinct areas indicates a heterogeneous mixture. 

A mixture is a combination of two or more pure substances in which each substance retains its individual properties. Concrete, most rocks, most metal objects, all food, and the air you breathe are mixtures that are often composed of many different substances. The composition of a mixture is variable. For example, the composition of salt water can be varied by changing the amount of salt or water in the mixture. 

Two types of mixtures exist. A heterogeneous mixture is one that is not blended smoothly throughout. Examples of heterogeneous mixtures include smoky air and muddy water. You may have to use a magnifying glass or even a microscope, but if you can identify bits of one or more of the components of a mixture, the mixture is heterogeneous. 

When scientists speak of the composition of matter, they are referring to the kinds and amounts of components of which the matter is made. On the basis of composition alone, all matter can be classified into two broad categories substances or mixtures. You have already learned that a pure substance is a form of matter with a uniform and unchanging composition. You also know that the intensive properties of pure substances do not change, regardless of the physical state or amount of the substance. But what is the result when two or more substances are combined  

A homogeneous mixture has constant composition throughout it always has a single phase. Let s examine the salt-water mixture using the eyedropper. A drop of the mixture from the top of the beaker has the same composition as a drop from the bottom of the beaker. In fact, every drop of the mixture contains the same relative amounts of salt and water. 

Homogeneous mixtures are also referred to as solutions. You are probably most familiar with solutions in a liquid form, such as cough suppressant medicine and lemonade, but solutions may contain solids, liquids, or gases. Table 3-3 lists the various types of solution systems and gives an example of each. Solutions are very important in chemistry, and, in fact, this textbook devotes an entire chapter to the study of solutions. 

Coins issued by the U.S. Mint are metal alloys. The combination of multiple metals gives the coins specific properties such as color, weight, and durability. 

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If the 244Pu/238U ratio in the fresh supernova debris is P and that in the interstellar matter (old debris) is Q, the initial Pu/238 ratio (a) in the mixture of matter from which the solar system was formed is... 

Similarly, the initial 120I/127I ratio (p) in the mixture of matter from which the solar system was formed is... 

The next problem will show the same difficulty with the unreflected usage of Le Chatelier s principle students should state whether the addition of a solid substance to a mixture of matter, which is in equilibrium, leads to the change of concentrations or not. 

A very important aspect of the understanding of matter is the separation of mixtures of matter into their consituent pure substances. Consider, the treatment of... 

The various heating methods produce a vapor that is a mixture of gas, very small droplets, and small particles of solid matter (particulates). Before droplets or particulates can coalesce, the whole vapor is swept into the plasma flame for analysis. Clearly, the closer the heating source is... 

Unusual behavior has also been observed in soHd mixtures of He and He. In principle, all soHd mixtures should separate as absolute 2ero is approached, but because of kinetic limitations, this equiHbrium condition is almost never observed. However, because of high diffusivity resulting from the large 2ero-point motion in soHd helium, this sort of separation takes place in a matter of hours in soHd mixtures of He and He (53,61). The two-phase region for the soHd mixture is outlined by the dashed curve in Figure 4. The two-phase dome is shallow, and its temperature maximum is 0.38 K. 

Air-laid pulp-forming lines generally consist of three or more forming heads ia tandem. Liae widths range from 1 to 3 m and operate at speeds of some 400 m /min. Web weights range from 70 to 2000 g/m at throughputs of about 1000 kg/h. Air-laid pulp lines can be modified to process mixtures of textile and pulp fibers and to accommodate the addition of particulate matter. 

Commercial condensed phosphoric acids are mixtures of linear polyphosphoric acids made by the thermal process either direcdy or as a by-product of heat recovery. Wet-process acid may also be concentrated to - 70% P2O5 by evaporation. Liaear phosphoric acids are strongly hygroscopic and undergo viscosity changes and hydrolysis to less complex forms when exposed to moist air. Upon dissolution ia excess water, hydrolytic degradation to phosphoric acid occurs the hydrolysis rate is highly temperature-dependent. At 25°C, the half-life for the formation of phosphoric acid from the condensed forms is several days, whereas at 100°C the half-life is a matter of minutes. 

Canadian and European practice (2—4) and geologists and archaeologists in the United States use bitumen or asphaltic bitumen as a synonym for asphalt, and apply asphalt to the mixture of bitumen and inorganic matter that is used for paving purposes. On the other hand, pitches and tars are derived from the destmctive distillation of coal, cmde oils, and other organic materials. 

Bitumen Soluble in Carbon Disuffide (ASTMD4). Asphalt is defined as a mixture of hydrocarbons that are completely soluble in carbon disulfide. Trichloroethylene or 1,1,1-trichloroethane have been used in recent years as safer solvents for this purpose. The procedure for these and other solvents for asphalt with Htde or no mineral matter are described in ASTM D2042. 

Pieces of coal are mixtures of materials somewhat randomly distributed in differing amounts. The mineral matter can be readily distinguished from the organic, which is itself a mixture. Coal properties reflect the individual constituents and the relative proportions. By analogy to geologic formations, the macerals are the constituents that correspond to minerals that make up individual rocks. For coals, macerals, which tend to be consistent in their properties, represent particular classes of plant parts that have been transformed into coal (40). Most detailed chemical and physical studies of coal have been made on macerals or samples rich in a particular maceral, because maceral separation is time consuming. 

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