Name Date Class
Chapter 2•Matter and ChangeEXPERIMENT
PHYSICAL AND CHEMICAL CHANGE
PURPOSE
To investigate the criteria used to distinguish between physical andchemical changes in matter.
BACKGROUND
Matter has both physical and chemical properties. A physical property isa quality or condition of a substance that can be observed or measuredwithout changing the composition of the substance. Color is an exampleof a physical property. During a physical change, some properties of asample of matter change, but the composition of the sample does notchange. Melting and dissolving are examples of physical changes. Achemical change produces matter with a different composition than theoriginal sample. A chemical property describes the ability of a substanceto undergo a specific chemical change. The ability to rust is a chemicalproperty of iron.
In this experiment, you will observe various materials and describetheir physical properties. You will then cause some of the materials toundergo changes. Based upon your observations, you will determinewhether the changes are physical changes or chemical changes.
MATERIALS(PER PAIR)(Student Experiment)
safety goggles
spatula
magnifying glass
magnet
12 small test tubes
test-tube rack
2 100-mL beakers
glass stirring rod
funnel
ring stand
ring support
evaporating dish
gas burner
watch glass
plastic wash bottle
(Teacher Demonstration)
small test tube
centigram balance
fume hood / crucible tongs
wire gauze
test-tube holder
9 pieces paper, 10 cm 10 cm
magnesium ribbon, Mg
sulfur, powdered, S
iron filings, Fe
sodium hydrogen carbonate,NaHCO3
sodium chloride, NaCl
sucrose, C12H22O11
sand
distilled water
coarse filter paper
2 pieces of exposed film
6M hydrochloric acid, HCl
gas burner
test-tube holder
magnet
Experiment 2 Physical and Chemical Change25
Name Date Class
SAFETY FIRST!
In this lab, observe all precautions, especially the ones listed below. Ifyou see a safety icon beside a step in the Procedure, refer to the list belowfor its meaning.
Caution:Wear your safety goggles. (All steps.)
Caution:Hydrochloric acid is very corrosive and can causeburns. (Steps 10, 12.)
Caution:Do not look directly at burning magnesium. Theintense light may damage your eyes. View the magnesiumreaction through exposed pieces of film. Do not inhale the smokethat is produced when magnesium burns. (Step 9.) Powderedsulfur is irritating to the moist membranes of the eyes, nose, andthroat. Avoid getting the dust into the air. (Step 6.)
Caution:Do not taste any of the substances or touch them withyour hands. (All steps.)
Caution:Hot glass looks just like cool glass. Once a test tube hasbeen heated over an open flame, it may take several minutes forit to cool. Be sure that test tubes are cool before handling them.(Step 11.)
Caution:Magnesium is extremely flammable. Keep unusedstrips away from open flames. (Step 9.)
Note:Return or dispose of all materials according to theinstructions of your teacher. (Steps 5, 13, 15.)
PROCEDURE
Part A. The Physical Properties of Matter
Record your observations for Part A in Data Table 1.
1. Label a separate piece of paper for each of the sevensubstances to be examined. Place two pieces of magnesiumribbon, one 5 cm long and one 1 cm long, on the paper labeled“magnesium.” Using the spatula supplied for each substance,transfer a pea-sized sample of the other substances to theircorrectly labeled papers.
2. Examine each substance with a magnifying glass. Record yourobservations in Data Table 1.
3. Test the effect of a magnet on each substance by passing themagnet under the sheet of paper.
4. In separate small test tubes, test the solubility of eachsubstance by mixing a small amount of each sample with 3 mLof distilled water. “Flick” each test tube to mix the contents.
5. Return the strip of magnesium ribbon in the test tube to itspaper. Follow your teacher’s instructions for proper disposal ofthe other materials.
26Chemistry Laboratory Manual
Name Date Class
Part B. Causing a Physical or Chemical Change
Record your observations for Part B in Data Table 2.
6. Mix the iron filings and sulfur on a clean piece of paper.Examine the mixture with a magnifying glass. Test the effect ofa magnet by passing the magnet under the paper. Give thismixture to your teacher for use in Part C.
7. Mix the sodium chloride and sand on a clean piece of paper.Examine the mixture with a magnifying glass, and test theeffect of a magnet.
8. Transfer the salt-sand mixture to a clean 100-mL beaker. Addabout 30 mL of tap water and stir. Record your observations.Prepare a filtration setup as shown in Figures 2.1 and 2.2. Filterthe mixture and record your observations. Pour about 10 mL ofthe filtrate into an evaporating dish. Convert your filtrationsetup into a setup you can use to heat the liquid in theevaporating dish. Heat the dish gently until the filtrate hascompletely evaporated. Examine both the dry residue in theevaporating dish and the wet residue on the filter paper.
Figure 2.1
Figure 2.2
Experiment 2 Physical and Chemical Change27
Name Date Class
9. CAUTION: Do not look directly at burning magnesium; look through the exposed film. Position a watch glass near the gasburner. Using crucible tongs, grasp one end of the 5-cm strip ofmagnesium ribbon and hold it in the burner flame until themagnesium ignites. Quickly position the burning magnesiumso that the combustion products fall on the watch glass.Compare the appearance of this product with that of theoriginal magnesium ribbon.
10. Place the unburned 1-cm strip of magnesium and thecombustion product from the watch glass into separate testtubes. Add 10 drops of 6M hydrochloric acid to each tube. Feelthe bottom of each test tube. Record your observations.
11.Put half of your sucrose sample into a test tube. CAUTION:When heating a test tube, never point the mouth of it at yourself or anyone else. Heat the tube gently in a burner flame andwatch carefully for changes. Periodically remove the tube fromthe flame and check for odors by fanning the fumes towardyour nose. Grasp the test tube with a test-tube holder and holdthe test tube about 3–5 inches from your nose while fanningthe vapors toward your nose.
Now heat the residue in the test tube more vigorously for 1–2minutes. CAUTION: Be sure the tube is cool before handling it.After cooling the tube, use a spatula to scrape some of theresidue into a clean test tube. Examine the residue and test itssolubility in water.
12.Transfer the sodium hydrogen carbonate sample to a test tube.Carefully add 5 drops of 6M hydrochloric acid. Touch thebottom of the test tube with your hand. Record yourobservations.
13.Follow your teacher’s instructions for proper disposal of thematerials.
Part C. Conservation of Mass (Teacher Demonstration)
Record your observations for Part C in Data Table 2.
14. Several samples of the iron-sulfur mixture from Part B will becombined in a clean, dry test tube. The mass of the test tubeand its contents will be determined and recorded. The test tubeis heated gently, then vigorously, for several minutes.CAUTION: This heating must be done in a fume hood. Afterheating is complete, the mass is remeasured and recorded.Examine the reaction product. The effect of a magnet on thereaction product will be tested.
15. Your teacher will properly dispose of the materials.
28Chemistry Laboratory Manual
Name Date Class
OBSERVATIONS
DATA TABLE 1: PHYSICAL PROPERTIES OF MATTERSubstanceandFormula / PhysicalState / Color / Odor / Dissolvesinwater / Effect ofMagnet
sulfur, S
iron filings, Fe
sodium hydrogen carbonate,NaHCO3
sodium chloride, NaCl
sucrose, C12H22O11
sand, SiO2
magnesium, Mg
DATA TABLE 2: OBSERVATIONS OF PHYSICAL AND CHEMICAL CHANGES
System / Observations
Fe and S mixture
—tested with magnet
NaCl and sand mixture
—mixed with water
—filtered
—filtrate allowed to evaporate
Mg
—burned in air
Mg
—reacted with 6M HCl
product of burning
—reacted with 6M HCl
C12H22O11
—heated
NaHCO3
—reacted with 6M HCl
Fe and S mixture
—heated
initial mass
final mass
Experiment 2 Physical and Chemical Change 29
Name Date Class
ANALYSES AND CONCLUSIONS
1. The following is a list of changes you observed in Parts B and C. Indicate whethereach change was a physical change or a chemical change and give reasons foryour answer.
a. Mixing iron and sulfur. (Part B, Step 6)
b. Mixing salt, sand, and water. (Part B, Step 8)
c. Burning magnesium. (Part B, Step 9)
d. Mixing magnesium and the product of burning magnesium with hydrochloricacid. (Part B, Step 10)
e. Heating sucrose. (Part B, Step 11)
f. Mixing sodium hydrogen carbonate and hydrochloric acid. (Part B, Step 12)
g. Heating iron and sulfur. (Part C, Step 14)
30Chemistry Laboratory Manual
Name Date Class
2. Was mass conserved in the reaction of iron and sulfur? Explain.
3. Except for the reaction between iron and sulfur, none of the reactions in thisexperiment can be used to demonstrate the law of conservation of mass. Explainwhy.
4. How do you decide whether an observed property of matter is a physical orchemical property?
5. What criteria are used to distinguish between a chemical change and a physicalchange?
6. State in your own words the law of conservation of mass.
Experiment 2 Physical and Chemical Change 31
Name Date Class
GOING FURTHER
Develop a Hypothesis
The black residue left in Step 11 has a smaller mass than the original sucrose sample.Propose a hypothesis to explain this loss of mass.
Design an Experiment
Propose an experiment to test your hypothesis. If resources are available and youhave your teacher’s permission, perform the experiment.
32Chemistry Laboratory Manual