Chemistry
Specific Heat of a Metal Lab
Name ______________________
Purpose:
To calculate the specific heat of a metal using measurements in a coffee cup calorimeter.
Safety:
Where your safety goggles and apron to protect yourself from hot materials.
Introduction:
In this experiment, you will use a coffee cup as a calorimeter to measure the
specific heat (specific heat capacity) of a metal. You will then compare your
experimental value to the known value, and calculate the percent error. Specific heat, an
intensive property, can be used to identify a substance. It is defined as the amount of
energy needed to raise the temperature of 1 gram of the substance by 1 degree Celsius.
To determine the specific heat of the metal in the experiment we will have to
make some assumptions. First, we will assume that no heat is lost or gained between our
system and the surroundings. Second, we will assume that the heat lost by the metal
sample equals the heat gained by the water surrounding it and no heat is transferred to the
cup or the thermometer. Lastly, we will assume that no heat is lost to the surroundings
during the transfer of the hot metal from the water bath to the cup. Assuming all of the
above you will be able to utilize the following formulas:
Heat gained by the water = Heat lost by the metal
Mass of water x 4.184 J/g °C x ∆T of water = Mass of metal x Cp x ∆T of metal
Procedure:
1.
Fill a beaker about half full with water. Place the beaker on the hot plate, and
heat the water to boiling (1 per table).
2.
Mass a sample of dry metal and record its mass in the data table.
3.
Place the metal sample carefully into the beaker of boiling water with tongs.
Wait 5 minutes to ensure the metal is the same temperature as the water.
(WHILE YOU ARE WAITING – do steps 4-7)
4.
Measure out exactly 50mL of water in a graduated cylinder. Pour the water
into the coffee cup.
5.
Nest the coffee cup in a 250mL beaker to prevent it from tipping over.
6.
Place a partial coffee cup on top of the first cup to serve as a lid. Insert a
thermometer through the hole in the top of the cup.
7.
Wait at least 2 minutes and then measure the temperature of the water to the ½
degree and record it in the data table.
8.
Using a second thermometer measure the temperature of the boiling water to
the ½ degree and record it in the data table. BE SURE TO HOLD THE
THERMOMETER IN THE CENTER OF THE BEAKER OF WATER AND
DO NOT LET IT REST ON THE BOTTOM.
9.
CAREFULLY, transfer the hot metal from the boiling water to the coffee cup
using crucible tongs and tilting the lid open. Immediately, replace the lid
securely and gently stir the water with the thermometer.
10.
Constantly, observe the temperature and watch for the highest temperature
obtained before the temperature starts to drop again. It may take a few
minutes. Record the highest temperature to the ½ degree in the data table.
11.
Remove the lid and pour the water down the drain. Carefully, dry everything
with paper towels. Repeat the process with a second metal sample and new
sample of water.
Lab Report:
1.
completed data and calculations page
2.
conclusion hand written on the back of the calculations page:
Include a general summary of the experiment, why specific heat is
a good property for identification of a substance, an explanation of
other properties that can be used for the identification of a
substance, and errors in the experiment (both human and those
beyond your control).
Data Table:
Name __________________________
Sample #1 – observations _________________________________________________
Mass of metal sample (g)
Mass of water (g)
Temperature of water in cup (°C)
Temperature of boiling water (°C)
Temperature of water and sample (°C)
Sample #2 – observations _________________________________________________
Mass of metal sample (g)
Mass of water (g)
Temperature of water in cup (°C)
Temperature of boiling water (°C)
Temperature of water and sample (°C)
Calculations: (show sample #1 on the left and sample #2 on the right below)
1.
Change in temperature of metal:
2.
Change in temperature of water:
3.
Specific heat of metal:
Mass of water x 4.184 J/g °C x ∆T of water = Mass of metal x Cp x ∆T of metal
4.
Percent Error in Specific Heat Determination: (show work)