1. What was the purpose of the lab?
The purpose of this lab was to find the specific heat of a metal, for the purpose of finding out which metal it is. We were to find the specific heat by using a hot plate, a calorimeter, water, and an electric thermometer.
2. What did I need to know before undertaking this lab?
The specific heat of a metal is the amount of heat per gram required to raise the substance by one degree Celsius. In this lab, it was crucial to know how to determine the specific heat. We had to start with this equation:
q = mcΔT
In this equation, "q" stands for heat energy gained, "m" means the mass of the substance, "c" means the specific heat, and "ΔT" stands for the change in temperature. Different metals have different specific heats, which we also needed to know.
Substance Specific Heat
Water 4.184
Aluminum 0.897
Brass 0.385
Copper 0.385
Lead 0.129
Stainless Steel 0.490
Zinc 0.390
We couldn't measure the temperature of the metal directly, or know the heat lost from the metal, without using the heat equation for water. All we need to do is solve the equation to find the heat energy gained for the water inside the calorimeter, then plug that in for the equation for the metal to find the specific heat. The heat gained by the water is the same as the heat lost by the metal. This will make more sense when the procedure is explained.
3. What did I do in the lab and what data was collected?
Procedure:
- Take the mass of the coffee cup(calorimeter). Record.
- Pour 100 mL of water into the coffee cup(calorimeter).
- Determine the mass of the water and coffee cup together and record.
- Find initial temperature of the water.
- Fill a beaker with 300 mL of water.
- Place on hot plate and begin getting water to boil.
- Obtain the sample of metal you will be using and measure its mass. Record.
- Place the metal into the beaker and continue heating.
- After 10 minutes, record temperature of the boiling water without the probe touching the inside of the beaker.
- Using tongs, remove metal from beaker and quickly place into coffee cup(calorimeter). Put the lid on quickly, and put the temperature probe inside the calorimeter.
- Wait until temperature is stable and record it.
- Do this procedure at least twice.
Data:
Trial #1:
Mass of Coffee Cup 2.985g
Mass of Coffee Cup with Water 97.7775g
Initial Temperature of Water in Cup 21.1°C
Mass of metal sample 68.205g
Temperature of boiling water 99.2°C
Final Temperature of Water In Cup 27.3°C
Trial #2:
Mass of Coffee Cup 3.397g
Mass of Coffee Cup with Water 92.633g
Initial Temperature of Water in Cup 21.5°C
Mass of metal sample 68.07g
Temperature of boiling water 99.4°C
Final Temperature of Water In Cup 28.1°C
4. What does the data mean? (analysis, calculations)
Trial #1:
- First, we need to plug in the specific heat of water, the temperature change of the water, and the mass of the water, to find the heat gained by the water.
- q = mcΔT
- q= (97.775g-2.985g)(4.184)(27.3°C-21.1°C)
q= (94.79g)(4.184J/g-°C)(6.2)
q= 2458.9J
- Second, we need to find the specific heat of the metal.
- q = mcΔT
- 2458.9J= (68.205g)c(99.2°C-27.3°C)
2458.9J= (94.79g)c(71.9°C)
c= 0.501J/g-°C
Trial #2:
- First, we need to plug in the specific heat of water, the temperature change of the water, and the mass of the water, to find the heat gained by the water.
- q = mcΔT
- q= (89.236g)(4.184J/g-°C)(6.6)
q= 2464.189J
- Second, we need to find the specific heat of the metal.
- q = mcΔT
- 2464.189J= (68.07g)c(71.3°C)
c= 0.508J/g-°C
The average of the two specific heats is 0.5045J/g-°C. This obviously won’t be perfect, because heat could have escaped when we were transporting the metal to the calorimeter from the beaker of boiling water.
5. Conclusion.
After going through the steps to find the specific heat of the unknown metal, we reached the conclusion that the specific heat is approximately 0.5045J/g-°C. This doesn’t fit any of the metals on the chart, but it most closely fits stainless steel.
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