CHM 130
Physical and Chemical Changes
Objectives
1. List physical and chemical properties of substances and explain how they are used in identification and
separation of substances.
2. Become familiar with the concepts of solubility and miscibility and gain experience with both.
3. Outline the distinguishing characteristics of physical and chemical changes.
Experimental
A. Characterization of Substances by Observations of their Physical and Chemical Properties
1. Look at the samples of the substances water, iodine, table salt, table sugar, ethanol, wax, copper (II)
sulfate pentahydrate and mineral oil listed in Data Table A. Fill in the data table with color, form
(liquid, crystal, powder, etc.) and any other properties you can observe.
2. Open the bottles and smell each substance carefully, as shown in the safety video. Which substances
might be identified by their odors? Record your observation on the data table.
3. Behavior upon heating. It is important to note whether a substance melts, burns (combusts), or
decomposes upon heating. Investigate this by using a small piece of aluminum foil (about 1 in by 1 in
square) with a shallow depression in the center to hold a drop of liquid, or a few crystals of solid. Place
the foil on the lab bench and bring a lighted match close to the substance. Hold the match near the
surface of the substance and observe what happens. Some changes occur slowly, and there may be
more than one change per substance. Record all observations in your data table.
B: Solubility and Miscibility
Solubility in water is another distinguishing characteristic of substances.
1. Fill 4 test tubes about 1/3 full with DI water. Place a few crystals (very small scoop) of salt into the
first test tube. Stir the mixture for several minutes with your stirring rod or for 1 minute with the vortex
mixer. Repeat the process using sugar in the second test tube, wax in the third, and CuSO4∙5H2O (the
blue solid) in the fourth. Classify the solid solubilities as none (nothing dissolved), moderate (some
solid dissolved), or high (all solid dissolved).
Two liquids are said to be miscible if they mix in all proportions. If two liquids are immiscible, a distinct
layer will form between them.
2. In 3 separate test tubes, make mixtures of water/ethanol, water/mineral oil, and ethanol/mineral oil.
Add about 1 to 2 mL of each liquid (note: 20 drops is about 1 mL) use different amounts of each liquid
so you can tell which liquid settles to the bottom if the liquids are immiscible. Mix the contents very
well, either use the vortex mixer or place your thumb over the top of the test tube and invert the tube
several times to mix completely. Record your observations after mixing. Dispose of mixtures in
bottles provided.
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C. Chemical and Physical Changes
1. Fill a test tube about 1/3 full with DI water. Fill a second test tube with about 1 inch of 1M HCl. Add
a small scoop of baking soda (NaHCO3) to each test tube, if necessary shake to combine. Compare the
changes and note how you know when a chemical change is taking place.
2. Fill 3 test tubes about 1/3 full with DI water, and a fourth test tube about 1/3 full with tap water. Add
one small scoop of salt to the first test tube, mix completely to dissolve the salt. Add one small scoop of
sugar to the second test tube, mix completely to dissolve the sugar. Add a few drops of 0.1 M AgNO3 to
each test tube. Be careful: silver nitrate stains hands. Compare the changes and note how you know
when a chemical change is taking place.
3. Sand the end of a copper wire until it is shiny, like a new penny. Light a Bunsen burner and using tongs
hold the end of the copper wire in the hottest part of the flame for a few minutes until a change called
oxidation is observed. Remove and cool the wire on a tile. Sand a small section of the wire that was in
the flame, and compare the interior appearance with that of the outer surface. Report your observations.
4. IN THE HOOD, your instructor will heat some solid I2 (iodine) in a flask placed in a warm water bath.
The changes you should observe are called sublimation and deposition. Observe closely and record
your observations when the test tube is removed from the boiling water.
5. Dispose of all chemicals in bottles provided. Matches should be soaked in water and then disposed of
in the paper trash.
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Name _______________________________________Section ______ Lab Partner ________________________
CHM 130LL Experiment #1 - Physical and Chemical Changes
A. Characterization of substances by observations of their physical and chemical properties
Substance (Formula)
Water (H2O)
Color
Form
Odor
Heating
Table Salt (NaCl)
Table Sugar
(C12H22O11)
Ethanol
(C2H5OH)
Wax
(CH2CH2CH2CH2)
Copper (II) sulfate
(CuSO4·5H2O)
Mineral oil
(a hydrocarbon mixture)
A1. Which of the above might be easily confused if you tried to distinguish them by appearance alone?
Record your answers as "water and sugar," or "salt, water, and iodine.” (Note these are not correct
answers.)
A2. If you were given an "unknown" colorless liquid which was one of the materials you tested, what
specific steps would you take to identify it using the techniques above?
A3. How would you identify a white solid unknown which was one of the materials you tested?
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B. Solubility and Miscibility
B1. Solubility
Observation
Solubility (high, moderate, or none)
Table Salt in H2O:
Table Sugar in H2O:
Wax in H2O:
CuSO4·5H2O in H2O:
Question B1a: In your 10 mL graduated cylinder, add about 2 mL of table salt and then add deionized
water until the liquid level reaches about 4 mL. Shake vigorously. Does all the table salt
dissolve? Based on your result here and your result in Table B1, can you see that solubility
depend on the relative amount of solvent (water in our experiments) and solute (what we
are adding to water)?
B2. Miscibility
Miscible or Immiscible
More dense liquid (if immiscible)
Water and Ethanol
Water and Mineral Oil
Ethanol and Mineral Oil
Question B2a: After you have mixed water and ethanol and shaken the test tube, is it possible to tell
which liquid is more dense? Why or why not?
Question B2b: If you have done your experiment carefully, you should be able to rank the 3 liquids in
order of increasing density. Show your ranking and explain your reasoning.
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C. Chemical and Physical Changes
C1. Dissolving NaHCO3:
Observation
Type of Change
(Physical or Chemical)
NaHCO3 in H2O:
NaHCO3 in HCl:
Using the results of the above test, how do you know there was a chemical change?
C2. Testing with AgNO3:
Observation
Type of Change
(Physical or Chemical)
Salt solution:
Sugar solution:
Tap H2O:
Deionized H2O:
Using the results of the above test, how do you know there was a chemical change?
C3. Heating Cu wire:
Observations
Type of Change
(Physical or Chemical)
Observations
Type of Change
(Physical or Chemical)
Inner Appearance:
Outer Appearance:
C4. Heating and Cooling I2:
Observation on heating I2:
Observation on cooling I2:
Using the observed behavior of Cu and I2, comment on the reversibility of chemical vs. physical changes.
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D. Extra Questions
1. List and define 3 chemical properties and 3 physical properties of substances you observed in this
experiment.
Chemical properties:
1.
2.
3.
Physical properties:
1.
2.
3.
2. Classify the following as a physical or chemical change, explain your choice:
Freezing a saltwater solution
Dissolving sugar in your coffee
The tarnishing of silverware
3. Carefully define and distinguish between melting and burning (combustion). Give an example of each
from this experiment.
4. Is the behavior of Cu in the flame most closely related to melting or burning? Justify your answer.
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