Experiment No.
Investigating Exothermic and Endothermic reactions
8
INTRODUCTION
If you have ever been hurt in a sport or just from doing
something that ended up hurting you, adults would have put an ice
pack on your injury to help heal you. Some cold packs are full of a
gel that freezes and remains cold for several hours. Another type of
cold pack is one in which a chemical reaction occurs that results in
a reaction that feels cold to the touch. This is the type of cold pack
that will be investigated in this experiment. Additionally, you will
preform several reactions and determine whether these reactions
are exothermic or endothermic.
MATERIALS
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Five Styrofoam cups
Distilled water
Graduated cylinder
Gloves
Scissors
Instant cold packs containing
ammonium nitrate and water
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Beaker
Metal spatula
Digital thermometer, Vernier
Magnesium turnings
.1 M sodium hydroxide
.1 M hydrochloric acid
.1 M sulfuric acid
PROCEDURE
1.
2.
5.
Turn on the computer.
Connect the vernier system to the computer using the USB
cable.
Connect the vernier system to a power supply.
Connect the temperature probe to the vernier system by
connecting the probe into the channel 1 port.
Open up the LoggerPro program.
6.
Place a Styrofoam cup in the beaker.
3.
4.
INVESTIGATING EXOTHERMIC AND ENDOTHERMIC REACTIONSINVESTIGATING 68
EXOTHERMIC AND ENDOTHERMIC REACTIONS
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
Measure out 10 mL of both sodium hydroxide and
hydrochloric acid.
Add one of the solutions to the Styrofoam cup. Record the
initial temperature of the solution using the vernier
temperature probe.
Then add the other solution to the cup.
Determine the temperature change.
Dump waste in the proper waste receptacle. Put Styrofoam
cup in the trash.
Repeat steps 7-11 with sulfuric acid and magnesium turnings.
Add 100 mL of distilled water to each of the five Styrofoam
cups
Shake the instant cold pack gently to move the water bag
and crystals to the bottom.
Cut off the top of the bag.
Pour the crystals into the beaker.
Measure out 5.0 g of crystals in the weigh boat.
Record the starting temperature of the water in the first cup
using the digital thermometer.
Add the 5.0 g of the crystals to the cup.
Start collecting data and stir with the thermometer.
You can stop collecting data when the temperature levels
out for more than 5 seconds.
Print out the graph created.
Repeat steps 1 through 10 using different amounts for each of
the different trials.
a. Trial 2: 10 g
b. Trial 3: 15 g
c. Trial 4: 20 g
Make sure to rinse the thermometer in distilled water before
starting a new trial.
Acknowledgements
Whyte, D. B. (2013, January 10). Cold pack chemistry: Where does the heat
go? Retrieved from http://www.sciencebuddies.org/science-fairprojects/project_ideas/Chem_p081.shtml#summary
Royal Society of Chemistry. (2008, October 29). Exothermic or endothermic?
Retrieved from http://www.rsc.org/learnchemistry/resource/res00000740/exothermic-or-endothermic
INVESTIGATING EXOTHERMIC AND ENDOTHERMIC REACTIONS 69
Data Tables
Reaction
Temperature
before mixing
°C
Temperature
after mixing °C
Endothermic or
exothermic
Sodium
hydroxide
solution + dilute
hydrochloric
acid
Dilute sulfuric
acid +
magnesium
turnings
Ammonium
nitrate + water
Amount of
ammonium nitrate
added to water
5.0 g
Temperature of water Temperature of water
before adding
after adding
ammonium nitrate °C ammonium nitrate °C
10.0 g
15.0 g
20.0 g
INVESTIGATING EXOTHERMIC AND ENDOTHERMIC REACTIONS 70
Pre-Lab Questions
1. What are some exothermic and endothermic reactions?
2. Which of these types of reactions feels warms to us? Which one
feels cold?
3. Why do these reactions feel the way they do?
INVESTIGATING EXOTHERMIC AND ENDOTHERMIC REACTIONS 71
Post-Lab Questions
1. Write the formula for the dissolving of ammonium nitrate in
water.
2. Describe the relationship between the amount of ammonium
nitrate that was dissolved in the water and the temperature
change.
3. Using your data, how much ammonium nitrate would have to
be added to get the solution to drop in temperature by 19
degrees Celsius?
INVESTIGATING EXOTHERMIC AND ENDOTHERMIC REACTIONS 72