Freezing and Boiling Point Effects

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The Effects of NaCl and EtOH on Water's Freezing and Boiling Points
(Watch out for tricks!)

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Starting materials

Distilled water
NaCl
3 pints Ethanol (at least 70% [rubbing alcohol])
Wooden spoons and plastic ice-tea spoons for stirrers
Large styrofoam cups (for freezing/melting point studies)
Sauce pans and electric hotplate (nothing with flames unless you are giving a lesson on how to contend with explosions!)
Thermometers that go from -10°C to +120°C
"Boiling chips" (small bits of crushed rock work well)

Preparations for the Day Before

500 grams of NaCl dissolved in warm water and made up to 2,000 ml. Call this "Stock Salt Soluton." Once made, make the following:
1. Take 600 ml of stock salt solution and add 300 ml of water to it
2. Take 300 ml of stock salt solution and add 600 ml of water to it
3. 1 liter of distilled water
4. Take a quarter of each of the above four (including the stock salt solution) and pour into icecube trays and freeze overnight.
5. Take a quarter of each of the above four and place in the refrigerator overnight.
6. The remainders of the 4 liquids are allowed to sit at room temperature for use in the boiling point studies the next day.
Take 1 pint of ethanol and add 1 pint of water
Take 1/2 pint of ethanol and add 1.5 pint of water
Take 1/4 pint of ethanol and add 1.75 pint of water
Take a quarter of each of the above four (including a pint of the "pure" alcohol) and pour into icecube trays and freeze overnight.
Take a quarter of each of the above four and place in the refrigerator overnight.
The remainders of the 4 liquids are allowed to sit at room temperature for use in the boiling point studies the next day.

Freezing/Melting Point Determinations

1 Into a styrofoam cup place two of the pure water ice cubes and about half that volume of the refrigerated pure water. Insert the thermometer into the cup and using the plastic spoon, stir. Keep reading the thermometer until the temperature steadies. Of course for the pure water system, the temperature should come to what reading? Record your result! You stir with the plastic spoon and not the thermometer for two reasons: you don't want to break the thermometer on the ice, and the spoon's paddle-shape is a better stirrer. Setup:
To the left
of Title.
2 One by one do the same with each of the other types of ice-cubes and their corresponding refrigerated liquids. (Obviously don't use any liquids that failed to freeze overnight.) Don't forget to record your data as you go!

Boiling/Condensation Point Determinations

3 Into a sauce pan place several inches of the pure water that was sitting at room temperature. Insert several of the bits of crushed rock and the thermometer into the pan. Turn on the heat to high. Using a wooden spoon, stir. Keep reading the thermometer until the temperature steadies. Of course for the pure water system, the temperature should come to what reading? Record your result! Then discard your boiling liquid in the following manner: Add approximately an equal amount of cold tap water to the pan and then carry the pan to the sink to dump it. In this way, if you bump into someone along the way, no one will be scalded. You stir with the wooden spoon and not the thermometer for two reasons: you don't want to break the thermometer on the ice, and the spoon's paddle-shape is a better stirrer. Setup:
To the right
of Title.
4 One by one do the same with each of the other types of room temperature liquids. Don't forget to record your data as you go!

CALCULATIONS

Calculate the concentrations of all liquids in terms of both %(w/v), molarity and molality
Calculate the values of freezing point depression and boiling point raising for all solutions.
Make three sets of graphs:
1. Depressions and raisings versus percent* concentration
2. Depressions and raisings versus molarity** concentration
3. Depressions and raisings versus molality*** concentration
From the graphs, determine whether the depressions and raisings correlate most closely with percent, molarity, or molality.

* A "one percent" solution (w/v) is made by adding 1 gram of the substance to a container and making it up to 100 ml with water. Note: the final volume is 100 ml.
** A "one molar" solution is made by adding 1 mole of the substance and then dissolving it up to a liter. Note: the final volume is one liter.
*** A "one molal" solution is made by adding 1 mole of the substance to one liter of water. Note: the final volume is more than one liter.

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1	Into a styrofoam cup place two of the pure water ice cubes and about half that volume of the refrigerated pure water. Insert the thermometer into the cup and using the plastic spoon, stir. Keep reading the thermometer until the temperature steadies. Of course for the pure water system, the temperature should come to what reading? Record your result! You stir with the plastic spoon and not the thermometer for two reasons: you don't want to break the thermometer on the ice, and the spoon's paddle-shape is a better stirrer.	Setup: To the left of Title.
2	One by one do the same with each of the other types of ice-cubes and their corresponding refrigerated liquids. (Obviously don't use any liquids that failed to freeze overnight.) Don't forget to record your data as you go!

3	Into a sauce pan place several inches of the pure water that was sitting at room temperature. Insert several of the bits of crushed rock and the thermometer into the pan. Turn on the heat to high. Using a wooden spoon, stir. Keep reading the thermometer until the temperature steadies. Of course for the pure water system, the temperature should come to what reading? Record your result! Then discard your boiling liquid in the following manner: Add approximately an equal amount of cold tap water to the pan and then carry the pan to the sink to dump it. In this way, if you bump into someone along the way, no one will be scalded. You stir with the wooden spoon and not the thermometer for two reasons: you don't want to break the thermometer on the ice, and the spoon's paddle-shape is a better stirrer.	Setup: To the right of Title.
4	One by one do the same with each of the other types of room temperature liquids. Don't forget to record your data as you go!