The Specific Heat of a Liquid
Purpose: To experimentally determine the specific heat of ethyl alcohol.
Principles: Heat is a form of energy which can pass spontaneously from an object at a higher
temperature to an object at a lower temperature. One of the properties of matter is that when heat
flows into a substance, the temperature is raised; if heat is withdrawn, the temperature is lowered
(provided that there is no change in state).
Traditionally, the unit of heat is the calorie (cal) which is defined as the quantity of heat required to
raise the temperature of 1 gram of water by 1 degree Celsius. In keeping with the gradual trend
toward SI units, the Joule (J) is now being used increasingly in chemistry. The conversion factor
between these units is 1 cal = 4.184 J. The quantity of heat Q required to cause a temperature
change in a substance depends on the nature of the substance and is proportional to the mass of the
substance (m) and the temperature change (∆t):
Q =(S.H.)∗(m)∗(Δt)
S.W. stands far specific heat, which is a physical constant far a given substance. The specific heat’s
value depends greatly on the nature of the substance and very little on the temperature.
The specific heat can be defined the quantity of heat energy required to raise the temperature of 1
gram of a substance by 1 degree Celsius.
The units for specific heat are:
g C
cal
°
Specific heat is an important quantity because it can be used to calculate the number of calories
required to heat a known mass of a substance from one temperature to another.
The higher the specific heat of a substance, the less its temperature will change when it absorbs a
given amount of heat. Conversely, the lower the specific heat of a substance, the more its
temperature will change when it absorbs a given amount of heat.
Among common substances that are part of our environment, water has a relatively high specific heat
(1.00 cal/g°C): it is thus a very effective coolant.
The water in oceans, lakes and swimming pools can absorb large amounts of heat without
undergoing extreme temperature changes, whereas the dry land surrounding these bodies of water
changes its temperature drastically when it absorbs a comparable amount of heat. This is why large
bodies of water act as natural temperature moderators; as a result coastal areas enjoy mild winters
and cool summers unlike desert areas which are well known for their extreme high and low
temperatures.
The specific heat of a liquid can readily be measured in a well insulated
container which gains or loses very little heat to the surroundings. A container
of this sort is called a calorimeter. In this experiment a small thermos (SnackJar)
will be used as a calorimeter.
Specific Heat of a Liquid
If this is not available two Styrofoam sups, one placed inside the other (placed into a 250 mL beaker
for stability) and covered with a piece of cardboard may be used instead.
A thermometer is then inserted through a hole in the cover of the calorimeter. When using the SnackJar,
a split rubber stopper will be used. When using Styrofoam cups a cardboard cover will be used.
The thermometer will be used to measure the temperature of the calorimeter contents.
Part I of this experiment, the specific heat of deionized water at room temperature will be determined.
Part II of this experiment, the specific heat of ethyl alcohol at room temperature will be determined.
In both parts of the experiment a precisely massed amount of deionized water and ethyl alcohol at
room temperature (cooler liquids) will be mixed with precisely massed warm water. The warm water
will be poured into the cooler liquids. At this time the heat flows from the warm water into the cooler
liquid. The temperature of the warm water decreases and the temperature of the cooler liquid
increases until they both reach the same temperature.
By determining the temperature of the warm water, the temperature of the cooler liquid and the
temperature of' the mixture at the time of mixing, the specific heat of the cooler liquid may be
determined.
Temperature measurements at the exact time of mixing are rather difficult to obtain since no reliable
temperature readings can be taken while the two liquids are being mixed. But we can determine this
temperature at the time of mixing using Microsoft Excel which will be explained in the calculation
section of this experiment.
During the mixing of the two liquids a small amount of heat is lost to the calorimeter which absorbs
some of the heat lost by the hot water. In this experiment the heat lost to the calorimeter is vey small
and will be assumed to be negligible. This provides the following equation:
Qlost by warm water = Qgained by cool liquid
Understanding that Q =(S.H.)∗(m)∗(Δt) the following equation is acheived:
( . . ) ( ) ( ) ( . . ) ( ) ( ) warmwater warmwater warmwater coolliquid coolliquid coolliquid S H ∗ m ∗ Δt = S H ∗ m ∗ Δt
warmwater Δt is the temperature change of the warm water. This is calculated from the temperature
of the warm water at mixing minus the temperature of the mixture at mixing. These
temperatures are only obtainable from the graph.
coolliquid Δt is the temperature change of the cool liquid. This is calculated from the temperature
of the mixture at mixing minus the temperature of the cool liquid at mixing. These
temperatures are only obtainable from the graph.
In the above equation the specific heat of warm water ( . . ) S H warmwater is given as 1.00 cal/g°C (this is
true for water between 60°C and 90°C.) The warmwater warmwater coolliquid coolliquid m , Δt , m and Δt are determined
experimentally. This allows for the calculation of the S H coolliquid . . .
Specific Heat of a Liquid
PART I: THE SPECIFIC HEAT OF WATER AT ROOM TEMPERATURE
1. Prepare cool water.
a. Measure about 70 mL of deionized water using your graduated cylinder.
b. Place your cool liquid calorimeter on the centigram balance
c. Tare the balance with the calorimeter on it.
d. Add the 70 mL of water from your graduated cylinder.
e. Record the mass of cool water in your notebook to the nearest 0.01g.
2. Prepare warm water.
a. Place a 250 mL beaker on a ring stand supported by a wire gauze.
b. Add between 150 to 200 mL of deionized water.
c. Heat the water to about 85°C
d. Measure about 70 mL of the hot water using your graduated cylinder.
e. Place the hot water calorimeter on the centigram balance
f. Tare the balance with the calorimeter on it.
g. Add the 70 mL of hot water from your graduated cylinder.
h. Record the mass of the hot water in your notebook to the nearest 0.01g.
3. Time = 0 minutes; Temperature Measurement
a. Record the temperature of the cool liquid in the calorimeter.
b. Record the temperature of the hot water in the calorimeter.
4. Time = 1 minute; Temperature Measurement
a. Record the temperature of the cool liquid in the calorimeter.
b. Record the temperature of the hot water in the calorimeter.
5. Time = 2 minutes; Temperature Measurement
a. Record the temperature of the cool liquid in the calorimeter.
b. Record the temperature of the hot water in the calorimeter.
6. Time = 3 minutes; Temperature Measurement
a. Record the temperature of the cool liquid in the calorimeter.
b. Record the temperature of the hot water in the calorimeter.
7. Time = 4 minutes; Temperature Measurement
a. Record the temperature of the cool liquid in the calorimeter.
b. Record the temperature of the hot water in the calorimeter.
8. Time = 5 minutes; mix
a. Pour the contents of the hot water calorimeter into the cool liquid calorimeter.
9. Time = 6 minutes; Temperature Measurement
a. Record the temperature of the cool liquid in the calorimeter.
b. Record the temperature of the hot water in the calorimeter.
10. Time = 7 minutes; Temperature Measurement
a. Record the temperature of the cool liquid in the calorimeter.
b. Record the temperature of the hot water in the calorimeter.
11. Time = 8 minutes; Temperature Measurement
a. Record the temperature of the cool liquid in the calorimeter.
b. Record the temperature of the hot water in the calorimeter.
12. Time = 9 minutes; Temperature Measurement
a. Record the temperature of the cool liquid in the calorimeter.
b. Record the temperature of the hot water in the calorimeter.
13. Time = 10 minutes; Temperature Measurement
a. Record the temperature of the cool liquid in the calorimeter.
b. Record the temperature of the hot water in the calorimeter.
14. Discard the water down the drain.
Specific Heat of a Liquid
PART II: THE SPECIFIC HEAT OF ETHYL ALCOHOL AT ROOM TEMPERATURE
1. Prepare ethyl alcohol.
a. Measure about 70 mL of ethyl alcohol using your graduated cylinder.
b. Place your cool liquid calorimeter on the centigram balance
c. Tare the balance with the calorimeter on it.
d. Add the 70 mL of ethyl alcohol from your graduated cylinder.
e. Record the mass of cool water in your notebook to the nearest 0.01g.
2. Prepare warm water.
a. Place a 250 mL beaker on a ring stand supported by a wire gauze.
b. Add between 150 to 200 mL of deionized water.
c. Heat the water to about 85°C
d. Measure about 70 mL of the hot water using your graduated cylinder.
e. Place the hot water calorimeter on the centigram balance
f. Tare the balance with the calorimeter on it.
g. Add the 70 mL of hot water from your graduated cylinder.
h. Record the mass of the hot water in your notebook to the nearest 0.01g.
3. Time = 0 minutes; Temperature Measurement
a. Record the temperature of the cool liquid in the calorimeter.
b. Record the temperature of the hot water in the calorimeter.
4. Time = 1 minute; Temperature Measurement
a. Record the temperature of the cool liquid in the calorimeter.
b. Record the temperature of the hot water in the calorimeter.
5. Time = 2 minutes; Temperature Measurement
a. Record the temperature of the cool liquid in the calorimeter.
b. Record the temperature of the hot water in the calorimeter.
6. Time = 3 minutes; Temperature Measurement
a. Record the temperature of the cool liquid in the calorimeter.
b. Record the temperature of the hot water in the calorimeter.
7. Time = 4 minutes; Temperature Measurement
a. Record the temperature of the cool liquid in the calorimeter.
b. Record the temperature of the hot water in the calorimeter.
8. Time = 5 minutes; mix
a. Pour the contents of the hot water calorimeter into the cool liquid calorimeter.
9. Time = 6 minutes; Temperature Measurement
a. Record the temperature of the cool liquid in the calorimeter.
b. Record the temperature of the hot water in the calorimeter.
10. Time = 7 minutes; Temperature Measurement
a. Record the temperature of the cool liquid in the calorimeter.
b. Record the temperature of the hot water in the calorimeter.
11. Time = 8 minutes; Temperature Measurement
a. Record the temperature of the cool liquid in the calorimeter.
b. Record the temperature of the hot water in the calorimeter.
12. Time = 9 minutes; Temperature Measurement
a. Record the temperature of the cool liquid in the calorimeter.
b. Record the temperature of the hot water in the calorimeter.
13. Time = 10 minutes; Temperature Measurement
a. Record the temperature of the cool liquid in the calorimeter.
b. Record the temperature of the hot water in the calorimeter.
14. Discard the water down the drain.
Specific Heat of a Liquid
Calculations using Microsoft Excel
Use the Microsoft Excel workbook called Chem 51 – Specific Heat of a Liquid.xls for this section.
Enter your data in the highlighted yellow boxes as shown below.
Print the worksheet and attach it to your datasheets.
Transfer the grayed data into your notebook and your datasheets.
NOTE: The calculations performed by Microsoft Excel uses the function called TREND. TREND
returns values along a linear trend. It fits a straight line (using the method of least squares) to the
arrays known_y's and known_x's. It returns the y-values along that line for the array of new_x's that
are specified.
Specific Heat of a Liquid
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Specific Heat of a Liquid
Specific Heat of a Liquid
Datasheet
Part I
Name: __________________
Date: ___________________
Partner: ________________
Mass of cold water ______________________ g
Mass of hot water _______________________ g
Time 0 minutes ............ Cold water temperature ________ °C ... Hot water temperature ______ °C
Time 1 minute .............. Cold water temperature ________ °C ... Hot water temperature ______ °C
Time 2 minutes ............ Cold water temperature ________ °C ... Hot water temperature ______ °C
Time 3 minutes ............ Cold water temperature ________ °C ... Hot water temperature ______ °C
Time 4 minutes ............ Cold water temperature ________ °C ... Hot water temperature ______ °C
Time 6 minutes ............ Mixture temperature _________°C
Time 7 minutes ............ Mixture temperature _________°C
Time 8 minutes ............ Mixture temperature _________°C
Time 9 minutes ............ Mixture temperature _________°C
Time 10 minutes .......... Mixture temperature _________°C
From Microsoft Excel:
Time 5 minutes ............ Cold water temperature ________ °C ... Hot water temperature ______ °C
Time 5 minutes ............ Mixture temperature _________°C
Calculations:
Heat lost by warm water: ( . . ) ( ) ( ) lost bywarmwater warmwater warmwater warmwater Q = S H ∗ m ∗ Δt
Heat gained by cold water: Qgained by cool liquid = Qlost by warmwater
Specific heat of cold water: ( . . ) ( ) ( ) gained by cool liquid cool liquid cool liquid cool liquid Q = S H ∗ m ∗ Δt
Specific Heat of a Liquid
Specific Heat of a Liquid
Datasheet
Part II
Name: __________________
Date: ___________________
Partner: ________________
Mass of Ethyl Alcohol water _______________ g
Mass of hot water _______________________ g
Time 0 minutes ............ Ethyl Alcohol temperature _______ °C ... Hot water temperature ______ °C
Time 1 minute .............. Ethyl Alcohol temperature _______ °C ... Hot water temperature ______ °C
Time 2 minutes ............ Ethyl Alcohol temperature _______ °C ... Hot water temperature ______ °C
Time 3 minutes ............ Ethyl Alcohol temperature _______ °C ... Hot water temperature ______ °C
Time 4 minutes ............ Ethyl Alcohol temperature _______ °C ... Hot water temperature ______ °C
Time 6 minutes ............ Mixture temperature _________°C
Time 7 minutes ............ Mixture temperature _________°C
Time 8 minutes ............ Mixture temperature _________°C
Time 9 minutes ............ Mixture temperature _________°C
Time 10 minutes .......... Mixture temperature _________°C
From Microsoft Excel:
Time 5 minutes ............ Cold water temperature ________ °C ... Hot water temperature ______ °C
Time 5 minutes ............ Mixture temperature _________°C
Calculations:
Heat lost by warm water: ( . . ) ( ) ( ) lost by warm water warm water warm water warm water Q = S H ∗ m ∗ Δt
Heat gained by ethyl alcohol: Qgained by cool liquid = Qlost by warmwater
Specific heat of ethyl alcohol: ( . . ) ( ) ( ) gained by cool liquid cool liquid cool liquid cool liquid Q = S H ∗ m ∗ Δt
Specific Heat of a Liquid
Specific Heat of a Liquid
Questions
Name: __________________
Date: ___________________
Partner: ________________
1. Calculate the Percentage Error in your experiment. (The theoretical value for the ethanol is
0.46 cal/g°C)
2. What assumption did you make that could explain the reason for your percent error?
3. The ∆T for alcohol is (greater, lesser) than the ∆T for water. (Circle the correct answer.)
4. The calculated specific heat of alcohol is (greater, lesser) that the specific heat of water. (Circle
the correct answer.)
5. ∆T and specific heat are (directly, inversely) proportional. (Circle the correct answer.)
