Friday, October 12, 2012

physical/chemical changes investigation

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.


What are the differences between physical and chemical changes?


Materials (per student)

Votive candle
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
Watch glass
Safety goggles
Table salt
2 test tubes
Dropper bottle of 0.1 M silver nitrate



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.



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?



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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