Links/Connections

WITHIN CHEMISTRY

Solutions and solution concentrations are very important in solubility and precipitation, chemical reactions, stoichiometry, chemical equilibria, acids and
bases, electrochemistry, separations, qualitative analysis, and rates of reactions. See the respective SourceBook modules.

BETWEEN CHEMISTRY AND OTHER DISCIPLINES

Biological sciences require a thorough understanding of aqueous solutions and concentrations. Health-related sciences—as pharmacy, nursing, medicine, and
dentistry—make extensive use of solutions. Solutions are also of concern in chemical engineering and related fields. Because both air and natural waters are
solutions, environmental scientists are considerably involved with solutions.

TO THE CONTEMPORARY WORLD

Personal

Consider the concentrations of key ingredients of various items in your home. Look at a box of breakfast cereal that is vitamin fortified and note the
concentration units that are used. Check other food and beverage items as well. If you have a bottle of tincture of iodine in your medicine chest, note the units of concentration that are used. Check other over-the-counter drug items; e.g., 0.09% saline, 3% hydrogen peroxide. How about shampoos? Cleaning solutions? Adhesives?

Community

Both air and natural water supplies are solutions. Water supplies typically have many ions and polar molecules dissolved in them. Consider the water supply
system in your community. Is your water considered a “hard-water” supply? Why is it called hard water? How can you test for the hardness? (See Biogeochemical Cycles module.)  How is the level (concentration) of chlorine in your water determined? Find out by contacting the appropriate “water
chemist” in your community. Are there pollutants in your water supply? How are they measured? Or are they? What about air pollution in your community?
Acid rain? More detailed information can be found in the Chemistry in the Community (ChemCom) units on water and the atmosphere.

Other ecological situations can be considered; e.g., DDT (an organic pesticide once in very wide use), accumulates in the fatty tissues of animals. Determine how this fact fits with the classic expression: “like dissolves like.” Also water passing through a landfill or garbage dump dissolves many substances that can
eventually  contaminate water supplies. These problems involving solutions can provide interesting class discussions, especially when probed to find answers
solutions!) to these problems.

Many workers in your community use solutions in their work, whether they know it or not. Have students think of persons who deal with solutions. A few
hints follow: Gasoline has additives in addition to its mixed hydrocarbon content. Antifreeze is an ethylene glycol/water solution with added rust inhibitors. Hair stylists use “permanent” wave solutions and shampoos, which may be either true solutions or colloids. Many food and beverage solutions can be obtained in stores and restaurants. [The brine (aqueous NaCl solution) used in pickles provides a good example of solution control. If the Clconcentration in the brine is too high, the pickles will shrivel up.] The use of solutions in the medical field was briefly noted above. Divers use a helium/oxygen gas mixture forbreathing in
order to avoid “the bends.” (Helium is not as soluble in water as is nitrogen.)

            The World

            The oceans provide the most abundant aqueous solution on earth. The seas contain 97.6% of the water on this planet. The water content of the ice caps and
            glaciers (1.9%), ground water (0.5%), rivers and lakes (0.02%), soil moisture (0.01%), and the atmosphere (0.0001%) is significantly lower. Although we
            normally consider ocean water as salt water, ions other than Na + and Cl – are also quite prevalent as are dissolved gases and organic materials. A
            consideration of the components of the ocean water is an interesting exercise. See the article on “Oceans and Seas” in the Encyclopaedia Britannica or the
            Chemistry of Seawater module for details.

            Naturally, the atmosphere is another important solution composed of nitrogen, oxygen, argon, carbon dioxide, water vapor, smaller amounts of sulfur oxides
            and nitrogen oxides, etc. Colloidal dust particles exist in both water and air supplies.

            Another important solution example is the eutrophication of fresh-water lakes and streams, i.e., the overgrowth of algae due to excessive nutrients (nitrates
            and phosphates, in particular) in the water from fertilizer runoff from homes, farms, golf courses, etc. and from detergents (phosphates).
 

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