Physical and Chemical Changes Investigation Lab
Background Information
Matter
is constantly changing. The two kinds of changes that occur in matter are
physical and chemical changes. In a physical change, no new substances are formed. However, physical properties such as size, shape, color, or phase may
change. Dissolving, melting, evaporating, and grinding are examples of physical
change.
As a result of chemical
change, one or more "new" substances with new and different
properties are formed. The new substances are different from the original
substance. Burning and the rusting of iron are examples of chemical change.
Problem
What
are the differences between physical and chemical changes?
Materials (per student)
Votive
candle
|
Scoop
|
Test-tube
rack
|
Aluminum
foil ~(15 cm x 15 cm)
|
Magnesium
ribbon (1 cm long)
|
Test-tube
clamp
|
Small
piece of paper
|
1
M hydrochloric acid
|
Matches
|
Watch
glass
|
Safety
goggles
|
Table
salt
|
Sand
|
2
test tubes
|
Dropper
bottle of 0.1 M silver nitrate
|
Procedure
1.Place an ice cube into a petri dish and leave on your lab bench. Record observations about any changes that occur to it during the lab.
2.
Light the candle and allow it to burn while you continue with the rest of the
investigation. Record your observations of the burning candle in the space
provided in Observations.
3.
Tear the piece of paper into small pieces and place them on the watch glass.
Place the watch glass and pieces of paper on the insulating pad. Light the
pieces of paper with a match and allow them to burn completely. Record your
observations of the burning paper.
4.
Add a small scoop of table salt to a test tube that has been half-filled with
tap water. Place your thumb over the top of the test tube and shake to dissolve
the salt. Record your observations. Using the dropper, add 5 drops of silver
nitrate to the salt water. Record your observations.
5.
Place a small piece of magnesium ribbon in a test tube. Add 5 drops of
hydrochloric acid to the test tube. Touch the bottom of the test tube with your
fingertips. Record your observations.
Observations
1.
What did you observe as the candle burned?
What was left after the candle burned?
2.
What did you observe as the paper burned? What was left after the paper burned?
3.
What did you observe when you added the salt to the water in the test tube and
shook it? What did you observe when the
silver nitrate was added to the salt water?
4.
What did you observe when the hydrochloric acid was added to the magnesium
metal?
Conclusions
1.
Identify each of the following as either a physical change or chemical change.
Give a reason for your answer.
a.
Melting candle wax
b.
Burning a candle
c.
Tearing paper
d.
Burning paper
e.
Dissolving table salt
f.
Mixing salt water and silver nitrate
g.
Cutting a piece of magnesium ribbon
h.
Adding hydrochloric acid to magnesium metal
2.
Describe two observations you might make when a physical change occurs.
3.
Describe two observations you might make when a chemical change occurs.
Critical Thinking and Application
1.
How could you show that dissolving the salt in water resulted in a physical
change?
2.
How could you show that adding acid to the magnesium ribbon resulted in a
chemical change?
3.
The following changes can sometimes indicate that a chemical change has
occurred. Explain how each change might result from a physical, not a chemical,
change.
a.
Change of color
b.
Loss of mass
c.
The substance seems to "disappear."
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