Instructor`s Copy Lab Worksheet

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Instructor’s Copy

Lab Worksheet – Pass The Salt

Data Table 1: The Effect of Temperature On Two Different Solutes

Observations Potassium nitrate Sodium chloride ice water

Not all is dissolved

hot water

All of solid is dissolved

ice water (2 nd

)

Crystals form

Situation

Most dissolved

No change

No change

Data Table 2: Factors Affecting A Gaseous Solute

Observation

Gas bubbles are visible*

When bottle is opened

Test tube is shaken

Test tube is heated

More bubbles are seen

More bubbles are seen

* Make sure students know that the bubbles are visible because the solute (carbon dioxide)

are “settling out” of the solution.

Questions:

1. In a solution of salt water,

(a) what is the solute?

salt

(b) what is the solvent?

water

2. Give five examples of solutions that you use on a regular basis. Identify the solute and solvent in

each of the solutions.

Answers will vary.

(a) ___________________________________________________________________________

(b) ___________________________________________________________________________

(c) ___________________________________________________________________________

(d) ___________________________________________________________________________

(e) ___________________________________________________________________________

3. Why is it necessary to keep all the conditions of an experiment identical except for the factor

being studied?

The only way to attribute a difference to one factor is to vary only one factor.

4. Give two example of gases dissolved in liquids.

(a) Carbon dioxide in water

(b) Nitrogen in blood (divers) or oxygen in blood to get to cells.

5. What are the two factors affecting solubility examined in this experiment?

(a)

temperature

(b)

type of solute

6. Based on what you observed in this experiment, how does temperature affect the solubility of

an ionic solute in water?

Increasing the temperature allows some ionic solids to dissolve better. It did not affect

sodium chloride much.

7. Based on what you observed in this experiment, what factors favor the dissolving of gases in

liquids?

Increase pressure (it didn’t come out of solution until the bottle was opened), not shaken,

and colder temperatures.

8. In terms of molecular motion, explain the differences between the dissolving of solids in liquids

and the dissolving of gases in liquids.

Answers will vary.

9. Which solid, potassium nitrate or sodium chloride, is more soluble in water at the temperatures

given?

(a) 10 o

C

sodium chloride

(b) 90 o

C

potassium nitrate

Synthesis

1. What effect would an increase in pressure have on the solubility of solids in liquids?

Almost no effect.

2. What effect would an increase in pressure have on the solubility of gases in liquids?

It would increase solubility.

3. The potassium nitrate solution, as you prepared it, is a saturated solution at the higher

temperature. What does this mean?

As much solid is dissolved as can be dissolved at any given temperature.

4. Many people drink both iced tea and hot tea with lemon juice and sugar to enhance the flavor.

Explain any differences in the rate of dissolving both the sugar and the lemon juice in the two

types of tea.

Answers will vary but may include: sugar will dissolve better in hot tea. Lemon juice just

mixes in, it doesn’t really dissolve.

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