Calorimeter Experiment: by Elizabeth Potoe and Andrew Van Alstyne
Prelab:
In this lab, you will be measuring the temperature of a reaction in water, and then using that to get the
Heat of reaction (qrxn). The reaction is a portion of a flameless heater from an military issue MRE being
put into water, and then using the temperature increase to calculate the heat of reaction.
The MRE heater is a powder made up of iron, magnesium metal, and table salt. When water is added to
this mixture, the result is an oxidation-reduction reaction between the magnesium metal and the water.
The reaction for this is unbalanced, you will need to balance the equation.
Mg + H2O -> Mg(OH)2 + H2 + heat
This reaction on its own is to slow to generate any significant amount of heat, so iron particles and
magnesium particles are added to increase the rate of reaction. When water is added to this mixture, it
dissolves the salt to create a salt-water electrolyte, which turns each particle of metal into a tiny battery.
Because the particles are in contact with each other, these batteries will quickly short circuit and burn
out, creating a heat through a process called “Supercorroding Galvanic Cells”.
To get the heat of reaction, you first need to solve for the heat of reservoir (qres). The equation you will
use is qres = C x mass x ∆T. The value you will use for heat capacity is 4.18 J/g x K, which is the heat
capacity of water. ∆T is the difference of the temperature of the water before and after the reaction.
The equation for ∆T is ∆T = Tfinal – Tinitial. You will need to convert your temperature readings to Kelvin.
After that, you need to find the mass. Your mass measurement will be the weight of the water plus the
weight of the reacting powder. Once you have this measurement and the other two, multiply them to
get qres.
Total mass = _______(grams of water) + _______(grams of powder)
C = 4.18 J/g x K
∆T = ______(Tfinal) – ______(Tinitial)
qres = ______(C) x _______(mass) x _______(∆T)
Once you have qres, you will need to find qrxn, the heat of reaction. To get this, take the negative of the
heat of reservoir.
qrxn = -qrsn
Sample Problem:
1.5 g of powder was added to 100 ml of distilled water. The initial temperature
was 19 ⁰C, and the final temperature was 30 ⁰C. What is the heat of reaction? (Hint: 1 g = 1 ml)
Procedure:
Step 1: Gather materials
Two Styrofoam cups, temperature probe, calculator, MRE heater strip, beaker for water, plastic weigh
boat, distilled water.
Step 2: Measure beaker on a scale, then measure out approximately 100 ml of distilled water into the
beaker. Record precise weight.
Step 3: Cut MRE heater strip in half, keep one half while giving the other to the next group.
Step 4: Measure plastic weigh boat, then pour the MRE heater powder in weigh boat. Measure weight
and record. Be careful not to inhale product, or touch face after this point.
Step 5: Construct calorimeter. Cut approximately 3/4 of a Styrofoam cup of, use the remaining 1/4 as lid
for container. Poke a hole in the lid to allow temperature probe to record.
Step 6: Put the measured amount of water in the calorimeter. Record temperature of the water.
Step 7: Add the MRE heater strip to the water and cover with the lid. Insert temperature probe to record
temperature. Mix contents manually by hand by softly shaking the cup.
Step 8: Wait for the temperature to peak, then record temperature and remove temperature probe.
Total mass = _______(weight of water) + _______(weight of powder)
C = 4.18 J/g x K
∆T = ______(Tfinal) – ______(Tinitial)
qres = ______(C) x _______(mass) x _______(∆T)
qrxn = -qrsn = ________
Post-Lab: a standard MRE heater has eight half-strips. How much heat would this heater generate?
Clean-up Procedure:
Step 1: Wash temperature probe under faucet, dry with paper towel.
Step 2: Without removing lid, take the calorimeter to pre-arraigned area for disposal. Do not dump
contents into a sink. Also take beakers and plastic weigh boats to same location.
Safety Precautions:
Keep powder away from face, avoid facial contact. Do not handle the powder any more than necessary.
Wash hands thoroughly afterwards. If powder comes in contact with eyes, wash immediately.
Grading Rubric
Pre-Lab Questions
3
Correctly answers
all of the
questions and
shows their work.
2
Sets up the
questions
correctly and gets
most of them
correct.
1
Answers some of
the questions
correctly, but
doesn’t show set
up.
Lab Set Up
Correctly sets up
the lab,
demonstrates
understanding of
lab set up.
Sets up
Calorimeter
properly, but
doesn’t prepare
as thoroughly for
measurements.
Lab Procedure
Gathers all data.
Lab Data
Calculations
Can accurately
calculate qrxn from
lab data.
Gathers most of
the data
Can
approximately
calculate qrxn from
lab data.
Sup-par job at
setting up
Calorimeter, and
isn’t prepared to
measure
materials
properly.
Gathers some of
the data
Has to guess qrxn
from lab data.
0
Gets most if not
all of the
questions wrong,
and doesn’t set
up questions
properly.
Calorimeter isn’t
usable, group
doesn’t set up lab.
Gathers little or
no data
Doesn’t calculate
qrxn.