Specific heat lab question

In summary, the goal of the lab was to find the specific heat of lead metal shot using the method of mixtures. The procedure involved measuring the room temperature and the temperature of water in an insulated calorimeter cup. The metal shot was then heated and poured into the water, reaching thermal equilibrium. The formula used to determine the specific heat was mmcm(Tm-Tf) = (mwcw + mccc)(TfTw). The best results were achieved when the final temperature of the mixture was approximately the same as the room temperature. This minimizes heat losses or gains from the room and provides more accurate results.
  • #1
emperrotta
11
0
For my most recent lab, the goal was to find the specific heat of lead metal shot. The procedure of the experiment consisted of using the method of mixtures. In this procedure, the room temperature Tr is first measured. Then, an insulated calorimeter cup is filled with water, and the temperature of the water Tw is measured. Meanwhile, lead metal shot is placed in a cup, which in turn is placed in boiling water until the temperature of the metal shot Tm reaches about 100 degrees Celsius depending on the calibration of the thermometer. Once the temperature of the metal shot reaches its high point near 100 degrees Celsius, the temperature is recorded and the metal shot is poured into the water. The metal shot then releases heat which is absorbed by the water until the mixture reaches thermal equilibrium and this final temperature Tf is measured.

The formula for specific heat is:
Q = c m dT
Q = heat released or absorbed
c = specific heat
m = mass
dT = change in temperature

With this procedure, once the metal is poured into the calorimeter the following occurs:
heat lost = heat gained
Qmetal shot = Qwater + Qcalorimeter

The final equation that was used to determine the specific heat of the metal shot was:
mmcm(Tm-Tf) = (mwcw + mccc)(TfTw)
mm = mass of metal shot
cm = specific heat of metal shot
Tm = temperature of heated metal shot
Tf = final temperature after metal shot was poured into the calorimeter with water
mw = mass of water
cw = specific heat of water
mc = mass of calorimeter cup
cc = specific heat of calorimeter cup
Tw = temperature of water before the metal shot is poured into it

It is stated in the lab procedure that the final temperature Tf should be above room temperature Tr by about as many degrees as Tw was below it such that Tf - Tr = Tr - Tw. If this is approximately the case, the best results will be achieved.

After all this, can someone tell me why satisfying the above scenario will provide the best results? Thanks in advance.
 
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  • #2
This would minimize heat losses to the room (or gains from the room) since, on average, the contents of the cup would match the room temperature.
 

1. What is the purpose of a specific heat lab?

The purpose of a specific heat lab is to measure the amount of heat needed to raise the temperature of a substance by a specific amount. This helps determine the specific heat capacity of the substance, which is the amount of heat required to raise the temperature of 1 gram of the substance by 1 degree Celsius.

2. How is specific heat measured in a lab?

Specific heat is measured in a lab by using a calorimeter, which is a device that measures the heat exchanged between a substance and its surroundings. The substance is heated to a specific temperature and then placed in the calorimeter, where its temperature change is recorded. This data is then used to calculate the specific heat capacity.

3. What factors affect the specific heat of a substance?

The specific heat of a substance can be affected by its molecular structure, density, and phase (solid, liquid, or gas). It can also be influenced by impurities or the presence of other substances in the mixture. Additionally, the temperature and pressure at which the measurement is taken can also impact the specific heat.

4. How is specific heat used in real-world applications?

Specific heat is used in a variety of real-world applications, such as in cooking, engineering, and climate science. In cooking, specific heat is important for determining cooking times and temperatures. In engineering, it is used to design materials that can withstand high temperatures. In climate science, it helps understand the energy transfer between the Earth's surface and the atmosphere.

5. What are some common units for specific heat?

The most common units for specific heat are joules per gram per degree Celsius (J/g°C) and calories per gram per degree Celsius (cal/g°C). Other units include joules per kilogram per degree Celsius (J/kg°C) and British thermal units per pound per degree Fahrenheit (BTU/lb°F).

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