INTRODUCTION:
In
order to change the temperature of something there must be a transfer of
energy. To heat up you must add energy, and to cool down you must remove
energy. In this activity we will explore the addition of energy to water,
which has a specific heat capacity of 4.184 J/g oC. The energy
source will be an ordinary cheezePuff. Yes, a cheezePuff. Think about it,
we eat food to get energy and if we feel we are eating too much food we
start counting Calories. Calories are simply a measure of energy and the
average cheezePuff ( 0.62 grams) contains about 2.7 Calories (2700 calories).
The main reason for using a cheezePuff is the air flow through the cheezePuff
structure. The apparatus used to determine the energy content of food is
known as a calorimeter which simply burns the food and measures the resulting
temperature change of a sample of water. This information is used with
the heat equation:
Q
= m cpDT
Q
= DTE
= “heat”m = masscp
= specific heat capacityT = temperature
We
will be using a highly simplified and inefficient calorimeter so
that we can explore the flow of the thermal energy.
Preliminary
Questions: Answer
on your individual paper
1.How
many flaming cheezePuffs do you think it would take to boil 1 cup (~255
mL) of water. The water originally is at “room” temperature (~20 oC)
Look
at the sample calorimeter provided by your teacher.
2.What
do you think is the source of the input energy?
3.Where
do you think the output energy will go?
4.How
efficient do you think the calorimeter is?
Available
Materials
(Get only the materials you need as you read through the procedure):
*
1 coffee can* 1 cheezePuff
*
1 large test tube * 1 food holder
(cork and T-pin)
*
1 temperature probe/computer* About
20 mL of water
*
1 graduated cylinder(1
mL H2O = 1 g H2O)
*
match(es)* electronic balance – 1
for class
PROCEDURE:
1.Collect
all materials, except the match.
2.Set
up a data table to record all data. (You must read the entire procedure
first to do this!)
3.Set
up the coffee can calorimeter according to the teacher’s instructions.
Each person should sketch the calorimeter below the preliminary questions.
4.Have
your teacher approve your data table and calorimeter before continuing.
5.Record
the actual volume of the water to the nearest 0.1 mL
6.Pour
the water into the test tube.
7.Place
the cheezePuff on the food holder.
8.Mass
the cheezePuff/holder using the electronic balance. Record this as the
initial mass of cheezePuff.
9.Place
the temperature probe in the water. Measure the temperature of the water
to the nearest 0.1 oC. Record this value as the initial temperature
of the water.
***
How to use the temperature probe:
Open
the Brain computer on the network and go to the Phy Sci Stuff folder.
·Double
click on the cheezePuff icon. If
needed
·Click
on the Temperature Probe Box and enter the probe calibration number as
requested.
This
number is on the probe’s cable.
·click
on the green “G” button in the toolbar, this will collect temperature data
for a maximum of 10 minutes in case you need it.
10.Have
your teacher approve your data before continuing.
11.Place
the cheezePuff about 2 cm below the test tube. Remove the coffee can and
ignite the cheezePuff. As soon as the cheezePuff is burning on its own
place the can back over the flaming cheezePuff. Pay attention to the test
tube, the heat may cause it to slip down.
12.After
the cheezePuff burns completely, allow the temperature probe to continue
collecting data until the temperature starts to go back down. When this
happens click the stop button in the top left of the screen.
13.Save
your data as cheeze2002 in your period folder.
14.Use
the graph of the data to determine the maximum temperature the water reached.
Record this value as the final temperature of the water.
15.Determine
the mass of the burnt cheezePuff/holder using the electronic balance. Record
this as the final mass of
cheezePuff
16.Have
your teacher approve your data before beginning the analysis.
ANALYSIS: Each
person should answer each question on your individual paper. Show K-U-E-S
where “calculate” is required.
1.Calculate
the change in temperature of the water.
2. Calculate
the mass of the water.
3.What
is the specific heat of water?
4.Calculate
the amount of thermal energy gained by the water.
5.Have
your teacher approve your group’s calculations.
6.Do
you think all of the energy released by the cheezePuff went into the water?
7.Add
to your individual sketch of the calorimeter to show the flow of thermal
energy during the burning of the cheezePuff.
8.Calculate
the mass of the cheezePuff that was actually burned.
9.Use
the actual value of energy/mass contained in a cheezePuff to calculate
the amount of energy that is theoretically contained in the mass you burned.
10.Have
your teacher approve your group’s calculations.
11.Calculate
the amount of thermal energy that did not flow from the cheezePuff into
the water.
12.Have
your teacher approve your group’s calculation.
13.Calculate
the efficiency of the coffee can calorimeter.
14.Have
your teacher approve your group’s calculations.
15.What
could be done to improve the efficiency of the calorimeter?
Cover
Sheet
Preliminary
Questions
Calorimeter
sketch
Analysis
Data
Table – attached to Data Recorder’s Report
Conclusion
Briefly
and completely, discuss your answers to the preliminary questions. Basically
you are re-answering the preliminary questions, only now you have experimental
evidence to support your answers, so an explanation is needed. Be sure
to specifically mention the when you have changed your answers.
Evaluation
Write
an evaluation of your group’s performance during this lab activity. Specifically
address each group member‘s performance of his/her specific job.(1 - 2
paragraph(s)
Write
an evaluation of the lab activity itself (1 paragraph).
Please
provide specific and useful information, not just, “I liked my group….this
was a fun lab….”. Also, remember to include supporting evidence for your
evaluation, this is a science class not a daytime talk show.