Are they selling Granite?
Introduction
The specific heat capacity is the amount of energy required to change the
temperature of one gram of a substance by one Celsius degree. Each substance
has a unique specific heat capacity. In this lab you will use a determination of the
specific heat capacity to identify an "unknown" rock sample.
Purpose
To determine if the sample of rock that you are given is granite by measuring the
specific heat capacity
Materials
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Safety goggles
Lab apron
Calorimeter
Graduated cylinder
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hotplate
Tongs
Stirrer
Thermometer
Safety
1. Thermometers are fragile. Be careful in handling them, and never use a thermometer
as a stirring rod. If you are using a mercury thermometer and it breaks, notify your
teacher immediately. Mercury vapors are poisonous.
Procedure
1. Put on your lab apron and safety goggles.
2. Measure EXACTLY 300.0 mL water and place it in the calorimeter. Record the
temperature of the water.
3. Record the temperature of the boiling water bath and carefully remove a rock
sample from the boiling water bath with a pair of crucible tongs.
4. Quickly place the rock sample into the calorimeter being careful not to overflow it.
Close the lid tightly and record the temperature every 30 seconds for about 5 minutes.
The temperature should first rise, level, and then fall. The maximum recorded
temperature will be used in the calculations of specific heat capacity.
5. Remove the rock sample from the calorimeter and place it on the counter to cool.
Record the number listed on the rock sample and refer to the chart to determine the
mass of the sample. Record this value in Table 1.
6. Empty the calorimeter and repeat steps 2-5 with another rock sample from the boiling
water bath.
7. Empty the calorimeter and gently place the rock samples back into the boiling water
bath. Add more water to the water bath if necessary. *Skip this step if this is the last
class of the day.
Cleaning Up
1. Return all materials to their proper locations.
2. Wash your hands thoroughly before leaving the laboratory.
Data Presentation
TABLE 1. Calorimetry Data Table
Trial #1
Trial #2
Initial temp. of water in calorimeter
Initial temp. of rock (boiling water bath)
Final temp. of water in calorimeter
(max temp)
Rock # and mass from chart
Mass of water in calorimeter (1ml = 1g)
TABLE 2. Calculation Summary
Trial #1
Trial #2
Heat transferred to the water
Specific Heat Capacity of Rock
% error
Data Analysis
Specific Heat Capacities (J/g°C) Water: 4.184 J/g°C
Granite: 0.803 J/g°C
1. Make a temperature versus time graph (hand drawn is acceptable) showing the
temperature data collected in step 4 of the procedure. There should be 2 lines (one for
each trial). Indicate the final temperature (max temp) of the rock that will be used to
calculate the specific heat capacity.
2. Use the formula q = m s t to calculate the heat transferred to the water in the
calorimeter in each trial. Show the calculations and record the values in Table 2.
2. How does the heat transferred to the water in the calorimeter compare to the heat
transferred from the rock in the calorimeter?
3. Use the formula q = m s t to calculate the specific heat capacity (s) of the rock
in each trial. Show the calculations and record the values in Table 2.
4. Assuming the identity of your rock is granite, what is the percent error in the specific
heat capacity? Show the calculations and record the values in Table 2.
% error = [(experimental s – known s)/known s] X 100
Conclusions
1. How is the final temperature of the rock determined?
2. Why is a hot water bath used to heat the rock?
3. Why is the volume of the water in the calorimeter measured when the mass of the
water is needed for the calculations?
4. Both of the following errors would cause a change in the calculated specific heat
capacity for the rock. Tell if the change would be to raise or lower the calculated value
of the specific heat capacity. Explain.
a. A significant amount of water is transferred with the hot rock.
b. The rock "cools off" as it is transferred from the hot water to the calorimeter.
5. Suppose that in the procedure a rock sample at room temperature was added to hot
water. How would this affect the percent error (higher, lower, or the same)? Explain the
reasoning.
6. Explain if the results would be similar if a beaker was used instead of the
calorimeter?
7. Do the data support or refute the claim that this rock material is composed of granite?
Explain the likelihood of the data to convince someone that the company is indeed
selling granite.
TABLE 1. Rock Numbers and Corresponding Masses
Rock #
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
Mass (g)
103.36
124.61
182.26
86.60
119.01
157.57
140.50
156.10
125.09
63.14
123.02
74.27
89.40
119.16
82.76
103.33
131.12
111.84
116.90
95.54
137.41
76.82
59.19
57.88
58.10
56.99
59.01
36.53
159.74
---51.27
171.00
163.81