Question

A student noticed that salt water provides more buoyancy (i.e. things float more easily) than freshwater, and asked the question: does the kind of salt affect the buoyancy of the water? She used six different kinds of salt to make salt water, and she made one solution of each type. All salt water samples were the same volume and the same concentration. The six kinds of salt used were: sodium chloride, potassium chloride, cesium chloride, sodium bromide, potassium bromide and cesium bromide. She then measured the maximum weight that could float for ten seconds in a small boat placed on the surface of each solution. Which of the following is the dependent variable in this experiment?

a. The size of the boat.

b. The type of salt used.

c. The volume of solution made.

d. The weight supported by the boat

e. The concentration of salt in the solutions

A red blood cell placed in 50% NaCl solution will

	a.	None of the choices are correct.
	b.	swell and eventually burst due to water intake.
	c.	stay the same size.
	d.	undergo crenation.

Answer 1

D is the answer.

There are two variables in the experiment:

* Dependent variables are those variable which depend on the independent variable. In an experiment, we can say the output of an experiment is the dependent variable. That's why buoyancy of boat is Dependent variable.

* Independent variable: They don't depend on other variable. It is the input in an experiment. Types of salt is an independent variable.

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Answer) D is the answer.

The hypertonic solution is the 50% NaCl solution. The water potential is lesser in 50% NaCl solution as compared to the red blood cell. Water movement occurs from the higher water potential to the lower water potential. That's why water moves outside the red blood cell via exo-osmosis. This leads to crenate the red blood cell.

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