Name __________________________________ Date: _________________ Class period ______
Lab Partner Name (s) _____________________________________________________________
Background information:
You and your friend’s feelings about a movie you’ve just seen may be very different.
You may disagree whether you liked the movie, or the movie’s intended meaning. Although you both have observed the same movie, your interpretations of the movie may differ.
Distinguishing between observation and interpretation is very important in chemistry. An
observation is a statement of fact, based on what you detect by your senses. An
interpretation is your judgment or opinion about what you have observed. A statement such as “the liquid is clear and colorless” is an observation. It would be an interpretation to say, without further testing, that the clear and colorless liquid is water.
The purpose of this experiment is to help you distinguish observations from interpretations while examining a chemical reaction. Try to make as many observations of the reaction as possible. There are two types of observations: A quantitative observation is an observation that involves measurements; a qualitative observation is a general description and does not involve measurement. “The liquid is hot” is a qualitative observation. “The temperature of the liquid is 95.0°C” is a quantitative observation.
Goals:
 Identify a physical and chemical change in the experiment
 Distinguish between observations and interpretations
 Classify observations as qualitative or quantitative
Equipment:
Goggles
Apron
Glass stirring rod
150mL beaker
Metal scoop
Thermometer
Materials:
Copper (II) chloride dihydrate (CuCl
2
·2H
2
O)
Aluminum foil, 8cm x 8cm
Safety:
 Copper (II) chloride will irritate eyes and skin. If you come into contact with it wash off immediately.
 While observing the reaction, DO NOT look directly into the beaker. Observe reaction from the side.
Procedure: As you perform this experiment, record your observations in the Data
Table on the next page.
1.
Obtain and describe a sample of copper (II) chloride dehydrate (CuCl
2
·2H
2
O)
2.
Fill the 150mL beaker about ¼ full of water. Without stirring, add your sample of copper (II) chloride crystals to the water. Record your observations of both the crystals and the water.
3.
Use the glass stirring rod to stir the mixture until the crystals are completely dissolved. Again, record your observations.

4.
Place the thermometer in the copper (II) chloride solution and record the initial temperature. DO NOT use the thermometer as a stirring rod!
5.
Place a loosely crumpled ball of aluminum in the solution and record your observations. Stir the mixture occasionally and observe for at least 10 minutes. Record the maximum temperature reached.
CAUTION: Observe the mixture from the side. Do not look directly into the beaker.
6.
To DISPOSE of the reaction: a.
Use your stirring rod to hold back the reacted aluminum and drain the liquid solution down the drain. Make sure the water is running. b.
Then place the reacted metal in the garbage.
Data Table:
System
Dry copper (II) chloride dihydrate
Observations
Unstirred copper (II) chloride in water
Stirred solution of copper (II) chloride in water
Copper (II) chloride solution plus aluminum foil
Initial temperature
(Before aluminum is added)
Final temperature
(After observing aluminum for
10 minutes)
Questions:
1.
Look back at your observations in the data table. List your qualitative and quantitative observations below:
Qualitative Quantitative

2.
Looking back at your observations, did you make any interpretations? If so, list them below. If not, give an example of what would have been an interpretation in this experiment.
3.
Which step in this experiment was a physical change? Explain.
4.
Which step was a chemical change? What did you observe that made you think this was a chemical change?
5.
Would you expect your observations OR your interpretations to closely match those of your classmates? Share your results with another lab group. What was
the same about your observation and interpretations? What was different?