OBSERVING A CHEMICAL REACTION
What is an observation and how does an observation differ from an interpretation or a conclusion?
An observation is a statement of fact, based on sensory data.
An interpretation or a conclusion is a judgment or opinion about what is observed.
A statement such as “the liquid is clear and colorless” is an observation. It would be an interpretation to say - "The clear colorless liquid is water" based on observations alone. As you observe the reaction in this experiment, try to make as many observations as possible. Make quantitative and qualitative observations.
A quantitative observation is an observation that involves a measurement.
(Mass, volume, length, and temperature are quantitative measures.)
A qualitative observation is a general description and does not involve a measurement. (Color, shape, odor, or visual description are qualitative observations.)
“The liquid is hot” is a qualitative observation. “The temperature of the liquid is 95.0 C” is a quantitative observation.
The purpose of this lab is to make observations about chemicals and chemical changes. You will make both qualitative and quantitative observations. You will record the temperature changes which occur as a result of a chemical change.
Copper chloride beaker
Al Foil stir rod
CBL w/ Temperature Probe
1. Obtain a sample of copper (II) chloride. Describe the dry crystals in detail and record
your observations in the Data Table.
2. Fill a 100-mL beaker about one-fourth full of tap water. Without stirring, add the crystals
of copper (II) chloride to the water. Observe both the crystals and the water and record
your observations in the Data Table.
3. Stir the mixture with the glass rod until the crystals completely disappear. Record your
observations in the Data Table.
4. Connect the CBL to the TI-83 calculator using the black link cable. Insert the temperature
probe into Channel 1 (at top of CBL).
5. Turn both units ON.
6. On the calculator, press PRGM, choose CHEMBIO, press ENTER twice.
7. Choose 1:SET UP PROBES, type 1. At SELECT PROBE, choose 1:TEMPERATURE.
8. At USE LOWEST AVAILABLE CHANNELS. ENTER CHANNEL NUMBER 1.
9. At MAIN MENU, choose 2:COLLECT DATA, then at DATA COLLECTION, choose
At **CONTINUE**, choose 1:USE TIME SETUP if your screen matched the above.
Then set your graph window as follows:
10. (a) Place the temperature probe in your copper (II) chloride solution.
(b) Press [ENTER] on your calculator.
(You are now collecting temperature vs. time data. The collection of data is indicated by a
blinking “sampling” on the CBL and the calculator is beginning to graph the data being
(c) After you see one dot appear on your graph, add the loosely crumbled aluminum foil to the copper (II) chloride solution.
(d) Your partner should stir the mixture with a glass stirring rod as data is being collected.
(e) Continue stirring until the CBL indicated DONE and your graph has been completed.
11. When the CBL unit indicates it is DONE collecting data, press [STAT] then [ENTER] on the calculator. Your time data is stored in L1 and temperature in L2. Record the initial, maximum, and final temperature of your reaction mixture in the
DATA TABLE 1
1. dry copper (II) chloride
2. copper (II) chloride in water
3. stirred solution of copper (II) chloride in water
4. copper (II) chloride solution plus aluminum foil
5. initial temperature
1. Define observation. ______________________________________________________
2. Define interpretation. _____________________________________________________
3. What observations were made in Item 1 of the Data Table? ________________________ _____________________________________________________________________
4. What observations were made in Item 2 of the Data Table? _______________________ _____________________________________________________________________
5. What is an interpretation of this observation? __________________________________ _____________________________________________________________________
6. What observations were made in Item 3 of the Data Table? ________________________ _____________________________________________________________________
7. What is an interpretation of this observation? __________________________________ _____________________________________________________________________
8. What observations were made in Item 4 of the Data Table? ________________________ _____________________________________________________________________
9. What is an interpretation of this observation? __________________________________ _____________________________________________________________________
10. Define qualitative observation. _____________________________________________ _____________________________________________________________________
11. Give an example of a qualitative observation made in this lab. ________________ _____________________________________________________________________
12. Define quantitative observation. ___________________________________________ _____________________________________________________________________
13. Give an example of a quantitative observation made in this lab. ____________________ _____________________________________________________________________