Calorimetry Lab
Steve's Book O' Labs
Lab 1: Calorimetry: Specific Heat of an Unknown Metal
Pre Lab Discussion:
The specific heat of a substance is defined as the amount of heat energy required to raise 1 gram of a substance by 1 degree Celsius. Specific heat can be found by using the following derived equation:
To find the numerical values for the variables of this equation a calorimeter must be used. The calorimeter works under the basic principle that when two bodies at different temperatures are in contact with one another, heat will flow from the warmer body to the cooler body. This principle is otherwise known as the law of conservation of energy, which states that energy is neither created nor destroyed. Using this principle the following statement is correct: (Heat Lost)=(Heat Gained).
Purpose: To find the specific heat of an unknown metal using a simple calorimeter.
Equipment: safety goggles test tube holder
cup, styrofoam 250 mL beaker
thermometer 100 mL beaker
test tube
Materials: water, metal pellets
SAFETY NOTE
Always wear safety goggles, tie back hair, and secure dangling clothing. Handle equipment with care, much of the equipment is fragile.
Procedure:
1. Obtain a styrofoam cup and pour 100 mL of water into it.
2. Let the water sit for 5 minutes, then find and record its temperature (TI).
3. Find the mass of 5-6 metal pellets (M).
4. Heat 175 mL of water in a 250 mL beaker to boiling. Place a test tube containing the pellets into the water. Allow to continue boiling for 10 minutes. Record the initial temperature of the pellets (TI). (NOTE: Water boils at 100 degrees Celsius.)
5. Remove pellets and immediately place them in the styrofoam cup.
6. Place the thermometer in the cup and watch it until it remains still. Record this as your final temperatures for both the water and pellets(Tf).
Data and Observations:
1. Water: TI = 21.0 C Tf = 25.0 C
M = 100. g
2. Pellets: TI = 104.0 C Tf = 25.0 C
M = 57.75 g
Calculations:
1. Find the amount of Joules given off by the pellets by using the observed mass, change in temperature, and the known specific heat of the water.
(Heat Released) = (Mass of Water)x(change in T)x(Specific heat of water)
H= (100 g) x (4.0 C) x (4.19J/g C) H= 1676 J
2. Find the specific heat of the metal pellets using the observed change in temperature, the measured mass, and the amount of Joules released (found in problem 1).
(1676 J) = (57.75 g) x (79.0 C) x C C= .37 J/g C
3. Find your percent error:
(Ask your teacher what kind of metal pellets you used then look up their specific heat)
PERCENT ERROR = (True Value) - (Experimental Value) X 100
--------------------------------------------
(True Value)
% error = (.38 J/g C) - (.37 J/g C) X 100 % error = 2.6%
-----------------------------
(.38 J/g C)
Questions and Conclusion:
1. Why is it a good idea to put the pellets in boiling water before placing them in the
styrofoam cup?
We used left the pellets in the boiling water to find an exact initial temperature for
the pellets, since we know water boils at exactly 100 C the pellets must also be at
100 C if they are left in the water.
2. What variables could have affected the outcome of your experiment?
Some variables that could have affected the outcome of my experiment are the length of time I left the pellets in the boiling water, the precision of my thermometer, the length of time the pellets were in the air before I placed them in the cup, and the loss of heat through the cup.
3. How might you do this experiment differently to get more accurate results?
I would try using a solid rod of metal or something other than pellets so I could place it directly in the boiling water rather than in a test tube, and hopefully come out with better results.
4. Conclusion?
I concluded that by using a simple calorimeter I could find the specific heat of an unknown metal. I continued to sharpen my skills using chemistry equations. I learned how to apply previous knowledge to design my own lab and found out that designing a lab is not as easy as it looks.