Instructions
Properties of matter are characteristics that help us to identify that matter because
each type of matter has its own unique set of properties. Properties may be determined
by changes in the physical form of the material. These are called physical properties
and include such things as density, melting point, and solubility. Other properties are
determined by how the material reacts or fails to react with other materials. In the
process of these determinations, the chemical composition of the material changes and
so these properties are called chemical properties. Both kinds of properties are very
useful in identifying a substance.
This experiment focuses on various white solids found around the house that may
appear identical to the casual observer. Becuase appearance fails as a distinguishing
characteristic, these chemicals must be identified by their chemical and physical
properties that are not readily apparent. Solubility (whether a substance dissolves or
not in another), pH (how acidic or basic the substance or its solution is), and reaction to
heat and other chemicals are simple tests that can be used to help differentiate
between several white household solids.
For example, both lye and salt readily dissolve in water, so solubility tests may not
distinguish between the two. But lye produces a basic solution while salt does not
change the acidity or basicity of its solvent. If we have an unknown substance known to
be either lye or salt, we can distinguish between them by testing the acidity or basicity
of their solutions with pH paper. pH paper is a special paper that has been treated with
chemicals so that it turns red in an acid that contains H+ ions, greenish-yellow in a
neutral solution, and blue in a base that contains OH- ions. (Ions will be studied in
Lesson 4). A lye solution would turn pH paper blue, and a salt solution would not change
the color of the pH paper.
You will be observing and recording information about the properties of six identified or
known white solids. Then you will be asked to identify an unknown> sample of one of
the six substances by observing its properties and comparing them to your previously
recorded data about the six solids.
You will be responsible for recording the data. Be very careful in making your
observations and recording them because you will need to use this data to identify your
unknown.
Table I: Household Chemicals Used in this Experiment
Item
Baking soda
Borax®
Chalk
Epsom Salt® Use
leavening agent
cleaning agent
antacid
soaking sore muscles Maalox® antacid Plaster of Paris® figurines Chemical Name
sodium bicarbonate
sodium tetraboratedecahydrate
calcium carbonate
magnesium sulfate heptahydrate
magnesium hydroxide
(active ingredient)
calcium sulfate hemihydrate Formula
NaHCO3
Na2B4O7•10H2O
CaCO3
MgSO4•7H2O
Mg(OH)2
CaSO4•½H2O Note: It is suggested that you carry out each of the six tests on only one substance at a
time. This way you will not get the substances mixed up. Instructions: steps Initial Steps:
1. Review this page carefully. You are required to complete the Lesson 3 Prelab
Quiz. Only after you have scored full points of the quiz, will you gain access to the
Lesson 3 Report Sheet in the Lesson 3 Experiment folder. Make sure that you print
out the Report Sheet. Prepare to write down your observations on the Report Sheet.
You may also want to print out this page to refer to while you perform the
experiment. 2. Put on your safety glasses and gloves before starting the experiment!!! 3. Use your wax pencil to mark six different small weighing boats with identifying
marks for the six different substances you will be obtaining. For example, BS for
baking soda or ES for epsom salt, etc. The six substances are baking soda, Borax,
chalk, Epsom Salt, Maalox, and Plaster of Paris. 4. Remove about ½ teaspoon of one of the six substances from the bag and place it
in a small weighing boat, Make note of what it is. Keep the rest of the Epsom Salt in
a safe place. You will need it to complete Lesson 5 experiment.Observe the physical
appearance of the substance and record on your report sheet. This should include
the color and texture of the substance. Four tests will be conducted: Solubility Test Acidity/Basicity Test Heating Test Reaction with Vinegar Test Specific instructions for these tests can be found in the following pages. From Lesson 2 Experiment Kit: 1 styrofoam cup 1 bag of Baking Soda® 1 bag of Borax® 1 bag of Chalk 1 bag of Epson Salt® 1 bag of Maalox® 1 bag of Plaster of Paris® 1 bag of white powder labled "Power A" From General Kit: Scoopula pH test paper with color chart Plastic petri dish with lid 5 thin stem plastic pipettes Glass stirring stick Crucible tongs 7 small aluminum weigh boats Wax pencil 10 mL graduated cylinder 50 mL beaker Candle 9" x 12" x 1-1/4" aluminum baking pan Safety glasses (for over other eyewear) that have the wrap around feature Disposable gloves (large size, twelve pairs) 13 x 100 ml test tube with a rubber stopper Home supplies: Measuring spoon set Clear white vinegar A pen or pencil to record observations 2 regular ceramic mugs Take out the test tube, make sure it is clean and set it upright in a ceramic mug.
If the test tube is dirty, wash it well and rinse with water BEFORE using. Use your scoopula to place an amount of solid about the size of a few grains of
rice (no more than 2 mm if measured from the bottom of the test tube) in the
bottom of the test tube. If unsure of this amount, use your ruler. Add enough room temperature water to fill the test tube half full. Put the small stopper in the test tube. It should fit snugly. Then shake the test
tube vigorously for one minute. Observe the contents of the test tube and record what you see on the Report
Sheet. Be as descriptive as possible, noting approximately how long it took for
the solid to dissolve. If the solid dissolved, the solution will be clear. If the
solution is milky white, it did not dissolve, but formed an insoluble emulsion. If
there is solid remaining at the bottom of the test tube, the solid is not fully
soluble. Remember your observations are going to be used to identify an
unknown sample of one these substances. If the solid did not totally dissolve, remove the stopper. Fill about ¾ of a
styrofoam cup with very hot tap water. If you wish, you can place the styrofoam
cup into the other ceramic mug to keep it stable. Immerse the test tube in the
hot water for approximately 2 minutes. Remove the test tube from the cup of hot
water. Once again, put the small stopper in the test tube. Then shake the test
tube vigorously for 1 minute. Observe the contents and record what you see. Keep the contents of the test tube for the next test. Acidity/Basicity Test
Rain water always contains some dissolved carbon dioxide that tends to make the water
slightly acidic. Depending on where your tap water comes from, your water may be
slightly acidic. If your tap water turns the pH paper red, substitute any brand of bottled
water for these tests.
Testing the pH of your tap water or bottled water:
Determine by looking at the color of the pH paper whether the solution is more acidic,
more basic or the same pH as your tap or bottled water.
Record your findings, which should include the color of the pH paper, the approximate
pH of the solution, and whether the solution is more acidic, more basic, or the same pH
as your tap or bottled water. Note: Test ALL solutions, even if you think that little of the solid dissolved.
12. Dip the clean glass stirring rod into tap or bottled water and then touch the rod to
a piece of pH paper, approximately ½ inch long. A general guide to the pH paper
colors follows. However, use the color chart that is included with the roll of pH paper
for the exact color and pH number.
Color
red
orange
light green
dark green
blue pH
1 to 3
4 to 6
7
8 to 10
11 to 14 Acidity / Basicity
strongly acidic
acidic
neutral
basic
strongly basic 13. On the Report Sheet, record the color of the pH paper, the pH number, and
whether the substance is acidic, basic, or neutral for the tap or bottled water. 14. Allow the solution from the solubility test to cool for at least 3 minutes (if it had
been heated ), then dip the clean, glass stirring rod into the solution and touch it to
an unused ½ inch piece of pH paper. 15. When done with your test, pour the solution down the drain and use some soap
and water to wash and rinse out your test tube. Then invert your test tube to dry.
One good way to do this is to put a paper towel at the bottom of a cup and then
invert the wet test tube in the cup. 16. Use the clean scoopula to place a pea-sized portion of the solid into one of the
aluminum weigh boats. If you have used all of the provided weigh boats, you can
make your own by cutting a piece of aluminum foil that is about 5 cm x 5 cm and
form it into a small dish by pressing it around the bottom of your 50 mL beaker from
your lab kit. 17. You will use the crucible tongs to hold the aluminum foil dish about 3 to 5 cm
above a candle flame. Have a heat resistant plate immediately next to the candle to
set the dish on after heating. 18. Light the candle and position the aluminum dish about 3 to 5 cm above the
flame. 19. Heat the dish and its contents for up to 1 minute, making note of how long it
takes for a change to take place. Some may melt immediately while others appear
to melt slowly. When you see the substance begin to melt or smoke, remove
the dish from the heat source immediately . Some solids may change from
being a crystalline solid to a powder, but don’t melt. Others may change color and
some don’t seem to change at all. Be sure your observations are thorough. 20. Using your crucible tongs, move the dish to the heat resistant plate and let it
cool. After all the white solids have been tested and the foil is cool, crumple up the
foil and throw in the garbage. Vinegar is a dilute solution of a weak acid, called acetic acid. It often produces bubbles
of gas when it reacts with substances. Look for bubbles of gas during this test.
21. Use your 50 mL beaker to obtain about 5 mL clear white vinegar.
22. With a thin stem plastic pipette, add 5 drops of vinegar to the solid left in your
weighing boat.
23. Record your observations on the Report Sheet.
24. Discard the solid and weighing boat, unless you wish to keep for verification of
your unknown "Powder A" later.
25. Repeat steps #6 to #25 with each of the other known substances in Table I.
Table I: Household Chemicals Used in this Experiment
Item
Baking soda
Borax®
Chalk
Epsom Salt® Use
leavening agent
cleaning agent
antacid
soaking sore muscles Maalox® antacid Plaster of Paris® figurines Chemical Name
sodium bicarbonate
sodium tetraboratedecahydrate
calcium carbonate
magnesium sulfate heptahydrate
magnesium hydroxide
(active ingredient)
calcium sulfate hemihydrate Formula
NaHCO3
Na2B4O7•10H2O
CaCO3
MgSO4•7H2O
Mg(OH)2
CaSO4•½H2O 26. After completing your observations of the six white solids, perform steps #1 to
#21 on your unknown sample in order to determine which of the original six
substances it is.
27. Clean-up: Empty the hot water from the styrofoam cup, dry it out well, and save
it for future experiments. Do NOT throw the cup away.
28. Go to the L03 Lab folder in ANGEL. In there, complete the Lesson 3 Prelab Quiz.
You won't have access to the Lesson 3 Report Sheet, which is located in the same
folder, until you get 100% correct in the quiz.

 

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