NAME:
PARTNER(S):
PHYSICAL AND CHEMICAL CHANGES
(21 points)
INTRODUCTION
Chemistry is a science that investigates physical and chemical changes in matter. The chemical changes
are also called chemical reactions. Often one can observe some visible changes when a chemical reaction
occurs. These include change in color, the production of a gas, the formation of a precipitate in a liquid, or
the release of energy. These visible changes are clues to what is happening to atoms within matter at the
atomic level.
PURPOSE
The purpose of this lab is to help the student understand the difference between physical and chemical
changes and to recognize each type of change when it occurs.
EQUIPMENT
Bunsen burner
test tubes
eye dropper
test tube rack
test tube holder
safety goggles
wire gauze
watch glass
50 mL beaker
magnet
crucible tongs
evaporating dish
CHEMICALS/MATERIALS
copper (II) sulfate pentahydrate (CuSO4∙ 5H2O)
0.1 M silver nitrate (AgNO3)
sodium chloride (NaCl)
powdered sulfur (S)
magnesium ribbon (Mg)
6M hydrochloric acid (HCl)
iron filings (Fe)
paper
matches
birthday candle
SAFETY NOTES:
1. When lighting a Bunsen burner, ignite the match, and then turn on the gas.
2. When heating substances in a test tube, ensure the test tube is labeled “PYREX” and be sure the open
end of the test tube is facing away from you and your neighbors. Always heat from the top of the material
to the bottom.
3. Hydrochloric acid is a corrosive. It will burn your skin. If you get some on you, rinse the area for 15
minutes under running water.
PROCEDURE
1. Obtain a candle, examine the wax part and record your observations.
2. Using the matches, warm the wax end of the candle and record your observations.
3. Examine the rest of the candle (wick end) and record your observations.
4. Warm the wax end of the candle with a match and stick it to the lab bench.
5. Light the candle and allow it to burn until it extinguishes itself. Record your observations.
6. Obtain a piece of paper (approximately 5 cm x 10 cm).
OVER
7. Tear the paper into small pieces and place them in an evaporating dish. Record your observations.
8. Place the watch glass/evaporating dish on the wire gauze.
9. Ignite the paper with a match and allow it to burn. Record your observations.
10. Obtain a test tube, 20 - 30 sodium chloride crystals, water, an eye dropper and silver nitrate.
11. Add 30 - 40 drops of water to the test tube.
12. Place sodium chloride crystals in the test tube. Record your observations.
13. Shake the test tube until the sodium chloride dissolves. If needed, add more drops of water.
14. Go to your instructor to obtain silver nitrate. Add 5-6 drops of silver nitrate to the NaCl-water mixture.
Record your observations.
15. Obtain two pieces of magnesium ribbon approximately 2 cm long. Record your observations.
16. Light your Bunsen burner.
17. Hold one piece of ribbon in the crucible tongs and insert it into the Bunsen burner flame. Record your
observations. CAUTION: Do not look directly at the burning Mg ribbon.
18. Cut the other magnesium ribbon into small pieces. Record your observations.
19. Place the pieces in a test tube.
20. Take the 50 mL beaker to your instructor and obtain 10 mL of hydrochloric acid.
21. Pour the hydrochloric acid into the test tube. Record your observations.
22. Quickly cover the first test tube with another test tube and collect the gas generated for several
seconds. The longer you collect the gas, the louder the “pop”.
23. Close the bottom of the second test tube with your fingertip. Record your observations.
24. Light a match and bring it to the opening of the test tube.
25. Remove your finger and bring the match closer. DO NOT INVERT THE TEST TUBE. Record your
observations.
26. Obtain a sample of copper (II) sulfate in a test tube. Record your observations.
27. Heat gently with a Bunsen burner for approximately 5 minutes. Record your observations.
28. Set the test tube in the test tube rack and allow it to cool. Record your observations.
29. Remove some of the CuSO4 from the test tube with a scoop and place it on the watch glass.
30. Add 3 – 5 drops of water to the CuSO4 and record your results.
31. Obtain a test tube containing a mixture of iron filings and powdered sulfur. Record your observations.
32. Pass a magnet alongside the test tube. Record your observations
DATA/OBSERVATIONS (13 points)
Make observations before and after each of the following steps. Record the information. Determine whether the
change is physical or chemical.
PROCEDURE
BEFORE
AFTER
1. Melting wax
2. Burning candle
3. Tearing paper
4. Burning paper
5. Dissolving salt
6. Adding silver nitrate
7. Burning magnesium
8. Cutting magnesium
9. Adding HCl to Mg
10. Igniting gas
11. Heating copper (II)
sulfate
12. Adding water
13. Mixture of Fe and S
OVER
TYPE OF CHANGE
QUESTIONS
(2 points) 1. What are two causes of chemical changes?
(2 points) 2. In what two ways is heat involved in chemical change?
(4 points) 3. List four types of observations that indicate when a chemical change has occurred.
STATION 1: STEPS 1 – 3
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STATION 2: STEPS 4 & 5
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STATION 3: STEPS 6 – 9
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STATION 4: STEPS 10 – 14
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STATION 5: STEPS 15 – 17
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OVER
STATION 6: STEPS 18 – 25
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STATION 7: STEPS 26 – 30
STATION 8: STEPS 31 & 32
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