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What is Dissolving?
Solubility curves
Polar and not-so-polar
The Universal Solvent
Squeaky Clean
100
What is the difference between a solute and a solvent?
A solute dissolves IN the solvent. A solvent does the dissolving.
100
What is "solubility?"
Solubility is the mass of a substance that dissolves in a certain volume of water at a certain temperature.
100
Give an example of a polar molecule.
Water
100
What is the chemical formula of the "Universal Solvent?"
H2O
100
What substance is required to get grease/oil out of fabrics?
Soap/detergent
200
Explain how water dissolves sodium chloride.
The polar areas of water molecules attract the oppositely charged ions of sodium chloride.
200
Compare the solubilities of sugar and salt, as temperature increases.
More sugar dissolves in water than does salt, at any temperature. At higher temperatures, MUCH more sugar dissolves than salt does.
200
Would you choose ethanol, water, or oil to dissolve a nonpolar molecular substance? Explain.
Oil would be the best solvent because nonpolar solvents dissolve nonpolar solutes. Like dissolves like.
200
Draw a picture of a water molecule, including its polarity.
Two hydrogens = the + region One oxygen = the - region
200
Explain why you cannot satisfactorily clean greasy dishes with plain water.
Water molecules ar epolar and are unable to dissolve (and thus remove) nonpolar oils from greasy dishes.
300
Explain the phrase, "Like dissolves like."
Polar solvents dissolve polar solutes, and nonpolar solvents dissolve nonpolar solutes.
300
What is a SATURATED SOLUTION?
A solution is saturated when...the solvent cannot dissolve any more solute at a given temperature.
300
Polar solvents dissolve polar solutes. What other solutes can they dissolve and why?
Polar solvents dissolve ionic solutes because ionic solutes have a charge that the polar solvents are attracted to.
300
How is frozen water different from all other substances in solid form?
Frozen water, or ice, floats on top of its liquid. In other words, its density is less than its liquid.
300
Why might hairspray get pen ink out of fabric when water cannot?
Like dissolves like. Water is polar, and since it does not dissolve ink, the ink must be nonpolar. Hairspray contains an alcohol that is nonpolar, so it dissolves the ink.
400
Explain why sugar dissolves faster than salt does in water.
Sugar is dissolved molecule by molecule. Salt is dissolved ion by ion. Salt ions are much, much smaller than sugar molecules, so it takes longer for salt to dissolve.
400
Compare the solubility of sucrose and carbon dioxide, as temperatures increase.
As the temperature increases, more sucrose dissolves and less carbon dioxide dissolves.
400
What percent of Earth's water is FRESH WATER?
ONLY 2.8% of Earth's water is fresh. The remaining 97.2% is ocean water.
400
Explain why water is polar.
A water molecule consists of 2 hydrogen atoms and 1 oxygen atom, which are covalently bonded. Because the oxygen atom has 8 positively charged protons, the electrons in the molecule "drift" slightly toward the oxygen end of the molecule, making it slightly negative. As a result, the hydrogen end of the molecule is slightly positive.
400
Many mechanics prefer to use waterless hand cleaners to clean their greasy hands. Explain: A. what kind of materials are likely to be found in these cleaners. B. why using these cleaners is more effective than washing with water.
A. They are likely to contain nonpolar materials. B. Because they can dissolve nonpolar greases and oils.
500
Suppose there are two identical fish tanks with identical conditions except for temperature. Tank A is maintained at a temperature of 5 degrees higher than is Tank B. Which tank could support the greater number of similar fish? EXPLAIN in detail
Tank B is cooler, so it could support more fish. This is because fish require oxygen, and gases dissolve better at cooler temperatures. This means that Tank B would have more oxygen dissolved in it, and it would be able to support more fish.
500
Given you knowledge of gas solubility, explain why a bottle of warm cola produces more "fizz" when opened thatn does a bottle of cold cola.
The solubility of carbon dioxide in cola decreases as the cola temperature increases. As a result, there is a greater release of excess dissolved carbon dioxide from warmer cola than from colder cola.
500
From each of these pairs, select the water source more likely to contain the higher conecentration of dissolved oxygen. Give a reason for each choice. A. a river with rapids or a calm lake B. a lake in spring or the same lake in summer C. a lake containing only black crappie or a lake containing only black bullhead
A. A river with rapids, because rapids promote mixing air with water. B. The lake in spring; it would be cooler, thus increasing the solubility of oxygen. C. Overall, black crappies require more oxygen than black bullheads to survive. Therefore, the lake containing the black crappies probably has more dissolved oxygen.
500
Why does water boil at a higher temperature than rubbing alcohol does? Use the terms POLAR/ITY, GAS, LIQUID, MOLECULES, INTERMOLECULAR FORCES
Water boils at a higher temperature than rubbing alcohol does because the POLARITY of its MOLECULES causes high INTERMOLECULAR FORCES. In other words, the positive end of each water molecule is attracted to the negative end of another water molecule, holding the molecules together. This prevents water from turning from a LIQUID to a GAS at low temperatures, as the molecules require a lot of energy, or heat, before the boiling point is reached. Rubbing alcohol does not have these strong intermolecular forces, so its boiling point is reached at cooler temperatures.
500
Explain how dishwashing soap gets the grease off a dirty pot. Use the terms HYDROPHYLLIC, HYDROPHOBIC, POLAR, NONPOLAR, GREASE, AND WATER, and RINSE
The hydrophyllic, or polar, end of the soap molecule attaches to water. The hydrophobic, or nonpolar end of the soap molecules attaches to the grease. The grease is then suspended in the water and can be rinsed away.