Brooke Nielsen
2rd hour
Introduction –
Every day people have to use different methods to determine unknowns. One example is
when a doctor has to diagnose a patient. When someone goes into the doctor, they have to
describe their symptoms. Then, the doctor compares their symptoms to symptoms of known
diseases or illnesses. This lab works in the same way to determine the specific heat, and in turn,
determine the metal. Specific heat is the amount of heat necessary to raise the temperature of
one gram of a substance one degree Celsius. Something that is also important to this lab is
knowing that waters specific heat is one calorie per gram of degrees Celsius. There are two
different types of reactions that occur; endothermic and exothermic. An endothermic reaction
absorbs heat from the surroundings and feels cold. An exothermic reaction is when energy is
released into the surroundings and feels hot. Endothermic and exothermic reactions are inversely
related; endothermic = - exothermic. Knowing this easily allows the data from the lab to
determine the specific heat. If the specific heat of an unknown object can be calculated, then the
identity of the unknown can be determined.
Materials and Methods –
First, a beaker of water was heated on a hot plate. Next, a metal was obtained and
physical observations were recorded. The unknown metal was then placed into the hot bath.
Two hundred mL of room temperature water was measured into a clean, dry calorimeter. Then it
was left to sit for two minutes. Next, the temperature of the hot bath was taken and recorded. At
this time, the water in the calorimeter sat for two minutes, so the temperature was recorded.
Then, the thermometer was slid into the top of the calorimeter. With crucible tongs, the metal
was quickly removed from the hot bath and placed in to the calorimeter. The top was placed on
immediately. The temperature was then recorded with a stop watch every thirty seconds for six
minutes.
Results –
TABLE 1: Specific Heat Lab Data
Mass of metal
Volume of water
Mass of water
Metal sample
57.99 g
200 mL
200 g
T I metal (Boiling water)
97.6 oC
T I water/calorimeter
16.93 oC
T f system
19.21 oC
T metal
-78.39 oC
T water/calorimeter
2.28 oC
s water
1 cal/goC
q water
456 cal
q metal
-456 cal
s metal
.1003 cal/goC
Equation 1 –
q=m*s*temp change
Heat in Calories –
q=200mL*1 cal/goC*2.28oC = 456 cal
Specific Heat of Metal –
-456cal=57.99g*s*-78.39oC =
.1003 cal/goC
Graph 1: Temperature vs Time
Temperature (degrees C)
19.5
19
18.5
18
17.5
17
16.5
0
100
200
300
400
Time (seconds)
Conclusion –
After completely the lab, the hypothesis was proved both correct and incorrect. The
specific heat was found to be .1003 cal/goC. The unknown bronze, dense, metal was determined
to be copper. However, on the list of specific heats for metals, nickel (rather than copper)
matched the actual determined specific heat. Nickels specific heat is .106 cal/goC and coppers is
.0920 cal/goC. However, it is known that nickel is not a bronze color. Therefore, copper was
next on the specific heat list, and matched the physical properties. The percent error was 9.02%.
This could have happen due to heat coming out of the calorimeter while putting the metal into
the calorimeter. Therefore assuming the metal was the only source of energy was probably not a
safe assumption. Also, it was not safe to assume the metal was always the same as the
temperature of the water. It could have taken time for the metal to change temperature compared
to the water. The mass of the water was assumed to be 200g because the volume was 200mL.
This also was a questionable assumption. Although these problems could have occurred causing
the 9.02% error, with common sense, the metal was still determined, and the hypothesis was
proved correct. Just like in this lab, determining unknowns can be used every day. A doctor can
determine an illness by ruling out other characteristics and matching up specific information.