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Date_______________
Synergy?
Background
Synergy is when two or more things working together increase their effectiveness in a task. In this
laboratory investigation, the effect of mixing solutes on the lowering of the freezing point of water will
be explored. How does the mixing of two solutes affect the lowering of the freezing point of water? Do
two solutes work together to decrease the freezing point or do they reduce the effectiveness of the
individual solutes on lowering the freezing point of water?
Objectives
1. After completing this laboratory investigation, the student will be able to describe the effect of mixing
solutes on the lowering of the freezing point of water.
Problem Statement
Determine the relationship between the mixing of two solutes effect on the freezing point depression of
water compared with the individual solutes effect on the freezing point.
Guidelines
The substances to be used for this laboratory investigation can be selected from the following
compounds: glucose, sucrose, sodium chloride, calcium chloride, magnesium chloride, potassium
acetate, and calcium magnesium acetate, and aluminum chloride.
Materials/Equipment (per group)
400 mL beaker (3)
Chemical compounds listed in Guidelines above (10 g)
Crushed or small cubed ice (300 g)
Deionized water
Electronic balance
Laptop or netbook computer
Styrofoam cup (3)
Temperature probes (3)
Weighing dishes (4)
Vernier LabPro w/Logger Pro Software
Procedure
1. Attach a Vernier LabPro with three temperature probes to the laptop and open the Logger Pro
software. Set the timing for 15 minutes.
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Date_______________
2. Place a weighing dish on the electronic balance and zero the balance. Measure out as exactly as
possible two 5 gram samples of a substance (Substance 1) from the chemical list. Repeat for a
second substance (Substance 2). Record the name of each substance and it’s mass to the
nearest hundredth of a gram in the data table.
3. Label three Styrofoam cups as 1, 2, and mixture.
4. Place a Styrofoam cup on the electronic balance and zero the balance. Add approximately 50 g
of the ice and then add distilled water until the mass is approximately 100 g. Record the mass of
the ice-water mixture to the nearest hundredth of a gram in the data table. Repeat this process
for the other two Styrofoam cups.
5. Place each Styrofoam cup inside of a 400 mL beaker and insert a temperature probe into each
ice-water mixture. Select Collect in Logger Pro, and stir each mixture until each temperature has
reached a minimum. Record this temperature as the freezing point of water.
6. Leaving the temperature probes in the ice-water mixtures, add each substance (Substance 1,
Substance 2, and a combination of Substances 1 & 2) to a separate cup and stir continuously
until all temperatures reaches a minimum. This may take some time but after the temperature
begins to rise noticeably in all cups, select Stop to end the data collection. Search the data
collected and record the minimum temperature of each solution in the data table.
7. Repeat the entire procedure using 2 completely different substances from the chemical list
(Substances 3 and 4).
Data Table
Trial 1
Substance 1
Substance 2
Substance 1 and 2 Mixture
1
2
Substance 3
Substance 4
Substance 3 and 4 Mixture
3
4
Substance name
Mass of substance (g)
Mass of ice-water mixture (g)
Freezing point of water (oC)
Minimum temperature of
solution (oC)
Trial 2
Substance name
Mass of substance (g)
Mass of ice-water mixture (g)
Freezing point of water (oC)
Minimum temperature of
solution (oC)
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Data Analysis
1.
2.
3.
4.
5.
Calculate the molar mass of each substance.
Calculate the number of moles each solute used.
Convert the mass of solvent used to kilograms.
Calculate the molality of each solution.
Calculate the freezing point depression for each solution.
Substance 1
Substance 2
Substances 1 & 2 Mixture
1
2
Substance 3
Substance 4
Substances 3 & 4 Mixture
3
4
Substance name
Molar mass of substance (g)
Moles of solute (mol)
Mass of solvent (kg)
Molality of solution (m)
Freezing point depression of
solution (oC)
Substance name
Molar mass of substance (g)
Moles of solute (mol)
Mass of solvent (kg)
Molality of solution (m)
Freezing point depression of
solution (oC)
Conclusions
1. How does the sum of the freezing point depressions of the individual substances compare to
their mixtures? Provide data to support your conclusion.
2. Do two solutes work together to decrease the freezing point or do they reduce the effectiveness
of the individual solutes on lowering the freezing point of water? Provide data to support your
conclusion.