Lab: Chemical and Physical Changes
Name:
Date:
A. Purpose: To investigate the criteria used to distinguish between physical and chemical changes
in matter.
B. Background: Have you ever thought of your eyes as powerful tools for studying chemistry?
Many of the properties of matter and the changes it undergoes can easily be determined through
careful observation. Physical properties include color, odor, density, solubility, and the state of the
matter. Chemical properties describe the changes that take place when new substances are formed
during a chemical reaction.
When matter undergoes a change, it is classified as either a physical change or chemical change.
During a physical change, only the size, temperature, or physical state of the substance changes.
Melting, dissolving, grinding, and evaporating are all physical changes. No new substances are
produced during a physical change. However, chemical changes always result in the formation of
one or more new substances. The rusting of iron, during which the new substance iron(III) oxide
forms from iron (Fe) and oxygen (O2), is an example of a chemical change. Evidences of chemical
changes are : a change of state (a gas or precipitate is produced), a change in color, a change in odor, or a
change in temperature.
The Law of Conservation of Mass states that in any chemical or physical change mass is conserved
(does not change). You will record the mass of the test tubes before and after combining them to see if
this law holds true for these reactions.
In this experiment you will observe a variety of materials and describe their physical properties.
You will then cause some of the substances to undergo changes. Based upon your observations,
you will determine whether the changes are physical changes or chemical changes.
C. Materials:
12 medium test tubes
Test tube rack
Stir rod
Filter paper
Funnel
Electronic balance
Sulfuric Acid (12M H2SO4) Teacher only handles
Test tube holder
0.1 M hydrochloric acid (1.0 M HCl)
Solid sodium carbonate (Na2CO3)
Solid calcium nitrate (Ca(NO3)2
Magnesium ribbon
Sand
Sodium chloride
D. Procedure:
1. Obtain two medium sized test tubes. Place a small amount (enough to fill 1/4 inch of the
scoopula tip) of solid sodium carbonate in to test tube 1. Fill the test tube about a third full
with distilled water and stir with the glass stir rod. Record two or three physical properties
of sodium carbonate in Table 1.1.
2. Repeat step one with calcium nitrate, placing it into test tube 2. BE SURE TO RINSE AND
DRY STIR ROD BETWEEN SOLUTIONS TO PREVENT CONTAMINATION.
3. Determine and record the mass of the combined test tubes in Table 1.2. Place a small beaker
on the balance and press the “Tare” button. The scale should read 0.00 g. Then add the two
test tubes and record in Table 1.2.
4. Note the temperature by feel of the two test tubes. Combine the contents of test tubes one
and two and observe. Record your observations in table 1.3. If no chemical change occurs,
indicate by writing “Physical change only.” Again note the temperature (Be careful, some
reactions can cause the test tubes to get very hot).
5. Determine the mass of test tubes 1 and 2 and their contents after combining them and record
in Table 1.2.
6. Clean and rinse the test tubes (Contents of the test tubes can go in the sink).
7. Repeat steps 1-6 using only distilled water in test tube 3 and dry sodium chloride (NaCl) in
test tube 4 (Do not add water to test tube 4 before combining test tube 3 and test tube 4).
8. Repeat steps 1-6 using only distilled water in test tube 5 and dry sand in test tube 6 (Do not
add water to test tube 6 before combining test tube 5 and test tube 6).
10. Repeat steps 1-6 using 1.0 M HCl in test tube 7 (already a solution, so no need to add more
water) and sodium carbonate in test tube 8.
11. Repeat steps 1-6 using 1.0 M HCl in test tube 9 and add a small piece (2-5 cm) of
magnesium ribbon to test tube 10( do not add water to test tube 6).
12. Fill a test tube 1/3 full with sugar, bring over to teacher to have Sulfuric acid added. Be
sure to hold test tube with test tube holder, teacher will demonstrate. Record results. Be
sure to set tube in proper disposal container!!
Table 1.1 Physical Properties
Test tube
Contents
Na2CO3
1
Distilled
water
Ca(NO3)2
2
Distilled
water
3
Distilled
water
4
Solid NaCl
5
Distilled
water
6
Dry sand
Physical properties
7
1.0 M HCl
8
Na2CO3
Distilled
water
9
01.0 M HCl
10
Magnesium
ribbon
(solid)
11
Dry sugar
Table 1.2 Masses of substances before and after combined.
Test tubes
Mass of combined
Mass of test tubes after
test tubes before
combining
combining.
1 and 2
3 and 4
5 and 6
7 and 8
9 and 10
11
(before acid)
(after acid)
Change in mass
Table 1.3 Chemical properties of substances.
Test tubes
Evidence of chemical change (if present)
1 and 2
3 and 4
5 and 6
3,4,5 and 6
7 and 8
9 and 10
11
12
E. Analyses and Conclusion:
1. Explain how to distinguish a physical property from a chemical property.
2. Explain how to distinguish a physical change from a chemical change.
3. List five indications of a chemical change.
4. List and describe the physical changes in the above combinations of test tubes and/or single
test tubes.
5. Which test tube combination(s) showed the formation of a precipitate (solid)?
6. Which test tube combination(s) showed the formation of a gas?
7. Which test tube combination(s) showed a temperature change?
8. Which test tube combination(s) showed a change in color?
9. State the law of conservation of mass.
10. Which, if any, of the above chemical reactions showed a change in mass? Explain.