Physical and Chemical Changes Lab
Name ____________________________
25 Points
Period _________
Date ____________
Introduction: As you read this it is probably fall. Summer flowers are fading and dying. Leaves are
changing from green to red, yellow and orange. All these changes involve chemistry.
As you have learned, chemistry is the study of matter and the changes that it undergoes. These changes
can be classified as physical, chemical, or nuclear. This lab will focus on physical and chemical changes.
When a physical change occurs, the physical properties of a substance – such as its size, shape, state, or
density – are altered, but its chemical composition remains the same. Examples of physical changes
include melting ice, crushing gravel, tearing paper, grinding pepper, and boiling water. No new
substances are formed as a result of these changes.
Chemical changes, also known as chemical reactions, result in the formation of one or more new
substances with different chemical properties and compositions from the original material. Examples of
chemical changes include plants dying, leaves changing color, paper burning, bananas ripening, bread
baking, or iron rusting. Some signs of chemical changes include a change in color, the formation of a
precipitate (a new solid substance that settles out of solution), the production and release of a gas, or a
change in temperature.
In this investigation, you will conduct tests on several substances and then use your data to determine
whether the resulting changes were chemical or physical. As you observe each change, remember to ask
yourself, “Has the change altered the identity of the substance?”
Pre-Lab Questions:
1. What are the 4 observable signs that indicate a chemical change is taking place?
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2. Define precipitate as it relates to this lab. _________________________________________________
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3. Identify the following as either a chemical (C) or physical (P) change:
a.
b.
c.
d.
e.
burning wood
dry ice changing to a gas
freezing water
ripening fruit
dissolving sugar in water
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4. Why are you instructed to feel outside the test tube after two chemicals are mixed, as in Steps 5 and 6
of this investigation? ________________________________________________________________
5. What are some safety cautions you need to observe during this investigation? ____________________
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Problem: How can you recognize and differentiate between physical and chemical changes in matter?
Procedure:
1. Put on your apron and goggles. Break off a small piece of wax from a white candle and place
it in a DISPOSABLE test tube. Holding the test tube with a test tube clamp, heat it gently over
the burner until the wax completely melts. Place the test tube in a beaker until it cools and
then throw the test tube in the glass disposal. Record observations in the Data Table.
2. With matches, light a white candle. Secure candle to the glass square by dripping wax onto
the square and then holding the base of the candle in to the molten wax until the wax hardens.
Allow the candle to burn for two minutes and blow out. Return the candle to the lab bench.
Record your observations in the Data Table.
3. Rip off a small piece of paper and place it in a watch glass. Place watch glass on the wire
screen as an insulating pad and ignite paper with matches. Dispose in the trash. Record your
observations in the Data Table.
4. Measure 5 mL of water in a graduated cylinder. Pour the water into a test tube and add a small
amount of sodium chloride, NaCl. Stir the contents to mix. Using medicine dropper, add 3
drops of silver nitrate (0.1 M AgNO3) to the NaCl-water mixture. Record your observations in
the Data Table. NOTE: SILVER NITRATE IS TOXIC AND CAN STAIN YOUR SKIN. WASH
ANY SILVER NITRATE OFF YOUR SKIN IMMEDIATELY.
5. Obtain a small piece of Magnesium ribbon and place it in a test tube. Add a few drops of
hydrochloric acid (6M HCl) to the test tube. Touch the side of the test tube before and after
adding the magnesium. Dispose of any remaining magnesium ribbon in the trash. Record
your observations in the Data Table. NOTE: HYDROCHLORIC ACID IS HIGHLY
CORROSIVE AND CAUSES BURNS. WASH ANY HYDROCHLORIC ACID OFF YOUR
SKIN IMMEDIATELY.
6. Grind several crystals of copper sulfate pentahydrate (CuSO4  5H2O) with the mortar and
pestle. Record results. Place a small scoop of the powder into a small test tube. Heat gently
over a Bunsen burner for 2 minutes, record results. Allow to cool for 10 minutes; then cool
completely under running water. Touch the bottom of the test tube with your fingertip, then
add a few drops of water and touch the bottom of your test tube again. Dispose in the sink.
Record your observations in the Data Table.
7. Using two pieces of weighing paper, place a SMALL amount of sulfur on one paper and a
SMALL amount of iron filings in the other. Run the magnet along the bottom of the papers.
Do not touch directly! Then, mix the two substances onto one paper and run the magnet along
the bottom. Dispose in the trash. Record your observations in the Data Table.
8. Heat the iron-sulfur sample under the fume hood for several minutes until the mixture glows.
CAUTION: Do not carry out this step unless a working hood is available. Noxious fumes are
produced that must be evacuated by a fume hood. Allow the sample to cool for 10 minutes.
Record its appearance. Test with a magnet. Record observations in Data Table.
9. Clean up your work area and wash your hands before leaving the laboratory.
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Observations: Data Table
STEP
1
Observations
2
3
4
5
6
7
8
Conclusions: Classify the following changes as physical (P) or chemical (C) Explain your answer.
Step
Change
1
Melting candle wax
2
Burning candle wax
3
Tearing paper
3
Burning paper
4
Dissolving NaCl
4
Mixing NaCl and AgNO3
5
Cutting Mg ribbon
5
Adding HCl to Mg
6
Grinding CuSO4 · 5H2O
6
Heating CuSO4 · 5H2O
7
Mixing Fe and S
8
Heating Fe and S
P/C
Explanation
3
1. Name two possible indications that a chemical change has occurred, using examples from this
investigation.
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2. A change in color does not always indicate chemical change. Explain why it could be the result of
a physical change.
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3. Answer the following questions using examples from this investigation to support your answers.
a. How can substances in a mixture be separated?
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b. How can substances in a compound be separated?
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4. Sodium chloride dissolves in water, leaving a clear homogenous mixture with no physical evidence
of the crystals with which you started. Design an experiment that you could perform to separate the
sodium chloride from the water.
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5. How could the experiment you designed in response to Question #4 differ if some sand was mixed
in with the sodium chloride before it was added to water?
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