Supersaturated Solutions Lab # 1 Name ___________________

True solutions are homogeneous mixtures of two or more pure substances, where the solute is

uniformly (evenly) dispersed throughout the solvent. Solutions can be unsaturated, saturated,

or supersaturated depending on the amount of solute dissolved in the solvent and the

temperature of the solution.

Unsaturated Solution

Less than the maximum amount of solute for that temperature is dissolved in the

solvent.

Saturated Solution

Solvent holds as much solute as is possible at that temperature.

Supersaturated Solution

Solvent holds more solute than is normally possible at a particular temperature.

These solutions are unstable and crystallization can be stimulated by adding a

seed crystal, scratching the side of the flask, or inserting a stirring rod.

As a solution is heated, solubility of a solid

solute will increase. This is illustrated by a

cup of coffee with sugar. The hotter the

coffee is, the more sugar that can be

dissolved into it. As the coffee cools down,

excess sugar comes out of solution and

settles on the bottom of the cup.

A supersaturated solution can be created

by heating a solution. Look at the diagram to

the right. The ∆ means change and indicates

that heat is added. If a saturated solution

with extra solute present is heated, the extra

solute will dissolve. As this solution is

cooled, it becomes supersaturated. This

means that it holds more solute than is

normally possible at that temperature. To

make the excess solute suddenly come out

of solution and form a solid, the

supersaturated solution needs to be slightly

disturbed in some way.

Purpose

The purpose of this lab is to produce and observe a

supersaturated solution through at different stages of

formations or morphs.

Materials

5.0 g Sodium Acetate - Na(C2H3O2)

Test Tube, test tube rack & test tube holder

5.0 mL of Tap Water

Beaker

Hot Plate

Stirring rod

Procedure

A. Put 5.0 g of Sodium Acetate in the bottom of the test tube.

B. Add 5.0 mL of water to the Sodium Acetate in the test tube. Use a stirring rod to stir the solution to help

dissolve as much sodium acetate as you can. Record your observations in the data table. At this point the

solution is at Morph 1.

C. Heat the test tube containing the solution you have just created by placing it in a hot water bath. Heat it

slowly and stir gently until the rest of the Sodium Acetate becomes dissolved. Record your observations

in the data table. At this point the solution is at Morph 2.

D. When all of the Sodium Acetate is dissolved, carefully remove the test tube from the water bath. Place

the test tube in a test tube rack and leave undisturbed on the lab counter for at least 15 minutes to cool.

E. After 15 minutes of cooling time have passed, carefully drop a crystal of solute into the supersaturated

solution and observe what happens. Record your observations in the data table. At this point the solution

is at Morph 3.

Data Table

The word morph

means change

when it is used as

a verb and form

when it is used as

a noun!

Draw what is occurring in the test tube and describe it in words.

Morph 1

Morph 2

Morph 3

Analysis Questions

Use the information in the introduction of this lab and your class notes to provide information to help

answer the following questions.

1. At Morph 1 was the solution unsaturated, saturated, or supersaturated? Explain your answer.

2. At Morph 2 was the solution unsaturated, saturated, or supersaturated? Explain your answer.

3. At Morph 3 was the solution unsaturated, saturated, or supersaturated? Explain your answer.

4. When sodium acetate dissolves in solution, it breaks up into a positive sodium ion and a negative

polyatomic acetate ion. This separation of ions in water is called dissociation. Write a chemical equation

that shows the process for the dissociation of Sodium Acetate in water in the space below. In doing so, use

brackets and +/- symbols to identify the ions.

5. During which Morph was all the Sodium Acetate fully dissociated into free moving ions?

6. During which Morph(s) was the Sodium Acetate present in both a solid and dissociated form?

7. Heating is important in the formation of a supersaturated solution.

What does heat do to the kinetic energy in a solution?

What does heat do to the speed at which ions and molecules move within a solution?

As a supersaturated solution cools, what happens to the kinetic energy in the solution?

As a supersaturated solution cools, what happens to the speed at which ions and water molecules

move?

8. 11The sudden changes that occur when excess solid solute comes out of a supersaturated solution are

pictured below.

Write a paragraph the fully describes how the supersaturated solution was formed and why the Sodium

Acetate came out of the supersaturated solution.

Solubility & Conductivity Lab #2

It is common knowledge that oil and water don’t mix, but do you know why? Some substances dissolve in each other and some do not. The purpose of this lab demonstrates how a characteristic of substances called Polarity affects whether substances dissolve in each other. It will provide you with the basis for classifying substance with respect to their polarity by knowing only that water is a polar substance.

EQUIPMENT: 24-Well plate CHEMICALS: Spatula or scoop Stirring-rod

Water, H20

Vegetable Oil Sodium chloride, Table Salt, NaCl

Disposable pipettes Ammonium chloride, NH4Cl

Paper towels Conductivity tester Goggles

Methyl alcohol, Wood Alcohol, CH3OH Sodium bicarbonate, Baking Soda, NaHCO3

Sucrose, Table Sugar, C12H22O11

Urea, NH2CONH2

PRINCIPLES: Determining polar nature, solubility, and conductivity

Chemists say that ‘like dissolves like,’ meaning that substances with similar chemical characteristics will dissolve in each other. Specifically, polar solvents tend to dissolve polar solutes, and non-polar solvents tend to dissolve non-polar solutes. Non-polar and polar liquids are insoluble. Chemists also know that some solutions conduct electricity while others do not. Those that do contain electrolytes which are ions in solution; if there aren’t any ions, the solution can’t conduct electricity.

It is possible to determine the polar nature of various substances knowing that ‘like dissolves like.’ Polar substances WILL DISSOLVE in WATER (a polar solvent), while non-polar solutes DO NOT. Non-polar substances dissolve only in other non-polar materials. Determine the polarity of each item in the table by testing its solubility in water and in oil. Then determine the presence of electrolytes in the solutions by using the conductivity tester.

PROCEDURE: Place the well plate so that 6 wells are horizontal and 4 wells are vertical. 1. Carefully add distilled water to the top 6 wells across the plate. This is one of your solvents.

2. Carefully add vegetable oil to the bottom 6 wells across the plate. This is one of your solvents. 3. Use a spatula (for solids) add a small amount (just enough to cover the TIP of the spatula) of the item to be tested. For liquid solutes add 2 to 3 drops. 4. Add one solute to one well of water then to one well of oil. Do this for each of the 6 solutes. 5. Using a glass stirring rod, mix the solutes into the solvents. Stir for up to 2 minutes. If you used too

much solute for the small amount of solvent, you may mistakenly think the solute is insoluble! 6. Check to see if the substance dissolves into the solvent to make a solution. Check for signs of solubility such as the disappearance of the solute. If you are unsure, repeat step 4, and watch to see if the substance dissolves. 7. Record your observations of solubility in the data table. 8. Write whether the substance is polar or non-polar, based on your observations, in the data table. 9. Dip the conductivity tester in each well to see if the solution conducts electricity. Wipe the tester off between each test. Record your observations in the data table. 10. Carefully pour the entire contents of the well plate into the waste beakers provided by the teacher.

CLEAN-UP: 1. Wash out the well plate, with soap and water, then dry with a clean paper towel.

2. Return all cleaned items to lab station and throw away the paper towels. Page 5of 28

Chemistry: Finding Solutions Name Station

Copyright © 2011 Stevens Institute of Technology, Center for Innovation in Engineering and Science Education; Page 6 of 28; All rights reserved.

DATA TABLE

SOLUTE DISSOLVES in

H2O?

DISSOLVES in OIL? POLAR or NON_POLAR?

Conducts Electricity?

NaCl

NH4Cl

CH3OH

NaHCO3

C12H22O11

NH2CONH2

OIL

Making a 1.0 Molar Solution Lab #3

Chemistry HS/Science

Unit: 10 Lesson: 02

Solutions are used in many everyday products. The preparation of a solution requires use of a

periodic table and careful laboratory procedures. Make your calculations using dimensional analysis

and significant figures.

Molarity (M) is defined as the number of moles of solute divided by the number of LITERS of solution.

Molarity = Moles of solute

Liters of solution

Procedures for the preparation of .25 L of a 1.0 M solution of copper (II) sulfate pentahydrate: • Calculate the molar mass of copper (II) sulfate pentahydrate Cu(SO4) ∙ 5H2O: ____________ g/mol

• How do you obtain one mole of copper (II) sulfate pentahydrate?

• How much water do you add to make a liter of solution?

• Why would using a pipette be useful when making this solution?

• Explain which would dissolve faster, whole crystals or crushed crystals. • Use the molarity equation to calculate how many moles you will need to make 250 mL (0.25

L) of 1.0 M solution of copper (II) sulfate pentahydrate. Convert moles to grams.

• Tell your teacher that your group is ready to make your solution. Be prepared to explain your process to make this 1.0 M solution.

Teacher approval • grams of copper (II) sulfate pentahydrate in a 250 mL volumetric flask. Fill

the volumetric flask about half full, and swirl the flask to dissolve the solute. When all of the copper (II) sulfate pentahydrate has dissolved, carefully fill the flask to the 250 mL mark using a pipette if needed. Swirl one more time.

• Clean up your lab table. Pour your copper (II) sulfate pentahydrate solution into a container, as

directed by your teacher.

Solution Dilutions

Each group will prepare 100 mL of a 0.25 M copper (II) sulfate pentahydrate from the 1.0 M solution you have already prepared. Use the dilution equation: M1V1 = M2V2 to calculate how much 1.0 M solution you need to make 100 mL of 0.25 M solution. Please show your work. Write your own procedures for diluting the solution.

Tell your teacher that your group is ready to make your solution. __________________ Teacher approval