There is a pan of water that been equilibrating
with the room for a sufficient time that it has reached room temperature at the
back of the lab. Use this for your 'room temperature' water.
In this lab you will study heat energy as it is transferred between objects. The
historical measure of heat energy is the calorie, which is the amount of heat
energy that must be added to 1 gram of water at 14.5 oC to raise its
temperature by 1oC.
For the first part of the experiment, you will be investigating the transfer of heat
energy from warm water to cool water. Heat lost by the warm water will be gained by the
cool water until thermal equilibrium is attained. The amount of heat exchanged depends on
the kind of material (water in this case); the amount of material; and the temperatures
involved. Heat energy is given the symbol Q. The heat gained of lost by an object
is defined by:
where M is the mass of the object, c is its specific heat
capacity (1 cal/g oC for water), Delta-T is the change in temperature of the object. You will use Logger Pro to acquire a
graph of temperature versus time. The graph should show three distinct
regions: a horizontal line starting at t = 0 that gives you room temperature; an
increasing region with a fairly steep (and possibly irregular) slope when you are adding the hot water;
and a gradual rise to a maximum followed by a slight fall in temperature due to
losing heat from the warmer water into the cooler room. You have the
information to calculate the mass of the room temperature water and the mass of
the hot water that was added. By applying conservation of energy - i.e. Qrt
+ Qh = 0, you can find the temperature of the hot water before it was
mixed with the room temperature water.
In the second part of the experiment, you will measure the specific heat of a metallic
object by investigating how the object effects the temperature of a known amount of water.
In preparation, start a beaker of water heating on the electric hot plate. We will
use boiling water to bring our metallic sample for the second part to a known initial
temperature. In this experiment you will measure all of the temperatures and
masses. Using the accepted value for the specific heat of water you will
be able to find the specific heat capacity of the metal mass. You will
compare your results to the accepted values for various metals and alloys and
choose the most likely candidate for the metal that makes up your mass.
Before you begin either experiment, check the room temperature reading of your temperature probe against the
liquid-in-glass thermometer. The two need not exactly agree, but they
should be close. Once this has been done you are ready to start the first part of the experiment.
Part 1 - Mixtures of water.
- Measure the mass of a stacked pair of dry Styrofoam cups. Add about
100 mL of ROOM TEMPERATURE water to the cups, and again measure the mass. Calculate the
mass of water.
- Place your temperature probe into the cup. Open Logger
Pro and set the experiment time to be 300 seconds. Allow the probe to
equilibrate for about a minute before proceeding.
- Using the other pair of cups, get a similar amount of
The water may have to run for a while to get hot. It is not necessary
to make a measurement with the graduated cylinder. Sometimes there is a
problem with the lab's hot water. If so, your instructor will give you
- Start the computer taking temperature data.
- Quickly, return to your experimental area and carefully pour the hot
water into the cup with the temperature probe.
- Use the temperature sensor as a stirring rod and continue to stir the
water until the temperature has reached its maximum value and started to drop, or until
the 300 seconds is up. Do not allow the sensor to rest on the sides or bottom of the cup.
- Find the change in temperature from the initial room temperature water
to the maximum temperature of the mixture. (You may find rescaling your graph and using
the 'Analyze', 'Examine' option to be useful.) You should be
cautious if you use the statistics option to find the maximum that there are
no spikes or other anomalies in your data - otherwise the reported maximum
might not be the physical maximum temperature.
- How much heat was gained by the room temperature water? How much heat
was lost by the hot tap water?
- Again measure the mass of the cups that contain the water and determine
how much hot water was added.
- Finally, calculate the initial temperature of the hot tap water.
- Print your graph to include in your notebook.
Part 2 - Finding the specific heat of a metal
- Once the water that you are heating starts to boil, suspend the 200
gram mass from a piece of string so that it is fully immersed. Allow the water to boil for
AT LEAST 5 Minutes. Do not allow the mass to rest on the bottom of the
- In the meantime, empty your cups and put about 100 grams of room
temperature water in a stacked pair. There are two approaches: The first is to add some
water and then measure the mass. Subtract off the mass of the dry cups and you know
how much water is present. The 100 grams is approximate, 90 to 110 will do.
You just need to know the mass. The second method is to realize that the
density of water is 1 g/ml, so if you add 100ml of water to your cups, the mass of water
should be (approximately) 100g.
- Use the liquid-in-glass thermometer to measure the
temperature of the boiling water - do not allow the thermometer to touch the
sides or bottom of the beaker. We
have all been taught that water boils at 100
Did you MEASURE the temperature of the boiling water to be EXACTLY 100
oC? If not, why do you think that your temperature
might have been different?
- Place your temperature probe in the cup of room temperature water and
allow it to come to equilibrium. Wait at least a minute before having the computer
start taking data. Stir gently and do not allow the probe to rest against
the wall or bottom. You should observe a horizontal region on your plot.
- Quickly and CAREFULLY bring the
mass over to your cup by means of the string. Move your temperature probe to the side of
the cup (but not touching the wall) and immerse the mass in your water. Gently lift and
lower your mass to stir the water while taking care that the hot mass does not touch the
- Continue until the temperature starts to decline or until the 300
seconds is up.
- Scale your graph so that the portion of interest fills
the graph, then print your graph.
- Again analyze your data and determine the heat capacity of your mass.
What material do you think the mass is made of? (hint: search the web for
the specific heat of metals/alloys). What do you
think could be done to make the experiment more accurate?
Last modified Feb