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General Chemistry Principles, Patterns, and Applications, 2011

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must be better.” Instead of using the recommended mixture (30% ethylene glycol/70% water), he decided to<br />

reverse the amounts <strong>and</strong> used a 70% ethylene glycol/30% water mixture instead. Serious engine problems<br />

developed. Why?<br />

9. The ancient Greeks produced “Attic ware,” pottery with a characteristic black <strong>and</strong> red glaze. To separate<br />

smaller clay particles from larger ones, the powdered clay was suspended in water <strong>and</strong> allowed to settle. This<br />

process yielded clay fractions with coarse, medium, <strong>and</strong> fine particles, <strong>and</strong> one of these fractions was used<br />

for painting. Which size of clay particles forms a suspension, which forms a precipitate, <strong>and</strong> which forms a<br />

colloidal dispersion? Would the colloidal dispersion be better characterized as an emulsion? Why or why not?<br />

Which fraction of clay particles was used for painting?<br />

10. The Tyndall effect is often observed in movie theaters, where it makes the beam of light from the projector<br />

clearly visible. What conclusions can you draw about the quality of the air in a movie theater where you<br />

observe a large Tyndall effect?<br />

11. Aluminum sulfate is the active ingredient in styptic pencils, which can be used to stop bleeding from small<br />

cuts. The Al 3+ ions induce aggregation of colloids in the blood, which facilitates formation of a blood clot. How<br />

can Al 3+ ions induce aggregation of a colloid? What is the probable charge on the colloidal particles in blood?<br />

12. ♦ The liver secretes bile, which is essential for the digestion of fats. As discussed inChapter 5 "Energy Changes<br />

in Chemical Reactions", fats are biomolecules with long hydrocarbon chains. The globules of fat released by<br />

partial digestion of food particles in the stomach <strong>and</strong> lower intestine are too large to be absorbed by the<br />

intestine unless they are emulsified by bile salts, such as glycocholate. Explain why a molecule like<br />

glycocholate is effective at creating an aqueous dispersion of fats in the digestive tract.<br />

Saylor URL: http://www.saylor.org/books<br />

Saylor.org<br />

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