Physical Science-Honors
Name
Date
Exothermic Reactions Lab Report
Question: In an exothermic reaction, how does increasing the amount of a reactant affect
the amount of heat energy that is transferred to the surroundings?
Hypothesis: In an exothermic reaction, if a greater mass of reactant is used, a greater
amount of heat energy will always be generated.
Procedure:
1. Calculate the mass of one 10.0 cm of Mg ribbon, one 20.0 cm piece, one 30.0 cm
piece, and one 40.0 cm piece and record.
2. Use a utility clamp and vertical support rod to position an extra large test tube (~50 mL
capacity) upright above the lab surface.
3. Use a graduated cylinder to measure 20.0 mL of 1.2M HCl, and add it to the larger
test tube.
4. Set up a LabQuest with a temperature probe. Make sure that the temperature probe
has been outfitted with a two-hole # 0 rubber stopper.
5. Use a wash bottle and a graduated cylinder to measure 10.0 mL of distilled water, and
add it to a small test tube (~15 mL capacity)
6. Place the temperature probe in the small test tube so that the # 0 rubber stopper is
secure in the top of the test tube. Store the test tube containing the water and the
probe upright so that it does not spill.
7. Start data collection with the LabQuest.
8. Place the 10.0 cm strip of Mg into the large test tube containing the HCl.
9. Place the small test tube (containing the temp. probe & water) into the larger test tube.
10. Watch the data collection process on the LabQuest carefully. After 3 min (180
seconds), the LabQuest may stop collecting data. If this happens, press the “Start”
button again, and select “Append” in order to keep collecting data to the graph for an
additional 180 seconds. Repeat this step as necessary, until you see the temperature
dropping for a full minute.
11. Use the LabQuest graph to find the minimum (starting) and maximum temperature
reached by the water, and record both values in the data table. Calculate T and
record.
12. Take the small test tube out of the large one, and rinse the outside of it in the sink.
Then, remove the temperature probe, dump the water in the sink, and rinse both the
probe and the test tube.
13. If there is any magnesium metal left over in the large test tube, add 10.0 mL of 3.0M
HCl to the large test tube, and wait for any sign of a chemical reaction to finish.
14. Pour the contents of the large test tube carefully into the sink, and rinse with water.
15. Steps 9-16 should now be repeated, using the 20.0 cm ribbon, the 30.0 cm ribbon,
and the 40.00 ribbon. Each time, start with fresh water in the small tube and replace
the HCl in the large tube.
Data:
Present all data in organized tables:
Data analysis:
Make a line graph showing the relationship between the mass of reactant used (x axis; Mass
of Mg in milligrams) and the thermal energy released by the reaction (y axis; Thermal
Energy in Joules). Use MS Excel and insert the line graph here.
Conclusion:
Write a conclusion here (a short paragraph using full sentences) in which you explain the
relationship between the manipulated and responding variable in this experiment. Include
your numeric data in your conclusion and explain what is says about the hypothesis. Use
the guidelines for conclusion writing. (“C.A.R.E.”)