Question

when compared to an ordinary liquid, water displays great many of strange behaviors that scientists do not fully understand. unlike other so - called \simple\ liquids. for example, water is the only liquid that expands when it freezes, which is responsible for lakes freezing from the top rather than the bottom. in addition, the new - discovered \water memory\ challenges our understanding of how molecules interact. waters unusually high surface tension is caused by cohesion, and allows insects to walk on waters surface. finally, the specific heat of water allows it to moderate environmental temperatures. these anomalies are of fundamental importance in many natural processes, such as the earths climate, and life itself.
jaundice is often a sign of a problem with the liver, gallbladder, or pancreas. jaundice is caused by excessive breakdown of red blood cells leading to a build - up of bilirubin, a yellow - orange bile salt. this build - up causes the skin and mucous membranes to turn yellow. doctors often use the hoys method to test for increased bile salts. sulfur powder is added to the urine sample, and if the powder sinks to the bottom, it is considered positive. in the image below, the sample on the left is plain water, while the sample on the right shows a problem with jaundice.
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1. which property of water is being demonstrated in this test?

a. cohesion
b. density
c. solvency
d. specific heat
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1. what is the purpose of the sample on the left?

a. it is a control.
b. it is a constant.
c. it is the dependent variable.
d. it is the independent variable.
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1. what is the independent variable in this test?

a. the bile salts
b. the sulfur powder
c. surface tension
d. cohesion

Explanation:

1. In the test, sulfur powder is added to detect bile - salts. The powder's behavior (sinking or not) is related to the density of the liquid it is in, not cohesion (attraction between like - water molecules), solvency (ability to dissolve substances), or specific heat (amount of heat per unit mass to raise temperature). So the property demonstrated is density.
2. In an experiment, a control is a standard against which other results are compared. The sample on the left is plain water, used to compare with the sample that may contain bile - salts. It is a control.
3. The independent variable is the factor that is deliberately changed or manipulated in an experiment. Here, the presence or absence of bile salts is what is being tested (manipulated), while the sulfur powder's behavior is the dependent variable.

Answer:

1. B. Density
2. A. It is a control
3. A. The bile salts