Determining Heat Capacity – An informal lab
INTRODUCTION:
In the Middle Ages, defenders of a castle sometimes poured hot liquids down onto the invaders who tried to storm
the fortress walls. The liquid of choice was usually any available oil. What properties of oil do you think prompted
this choice? This exercise will allow you to discover a chemical principle that has had many practical applications
over the centuries, although today we look upon some of them as less than exemplary.
You know from experience that it takes much longer to heat a large pot of water than it does a small pan of water.
You reason that there is more water to be heated in the larger sample, and that is correct. You also know that the
longer heating time involves a larger amount of heat. We say that the larger sample has a larger heat capacity. The
heat capacity of anything – whether solid, liquid, or gas – depends on the amount of the material in the sample as
well as its composition. For example, every gram of water requires the same amount of heat on warming from room
temperature to 100oC. It follows that the larger the sample, the greater the amount of heat needed to reach the
boiling point.
In this lab you will find the heat capacity of a lead sinker. You will do this by finding the mass of the sinker, warming
it to the boiling point of water, placing it in a sample of room temperature water in a calorimeter, and measuring the
temperature change of the water sample. From the data collected you will then calculate the heat lost by the sinker
to the water and thus the lead sinker’s heat capacity. A calorimeter works on the principle that the heat gained by
one system is equal to the heat lost by another system. In this lab we will assume that the heat gained by the water
is equal to the heat lost by the lead sinker.
PRE-LAB QUESTIONS: Answer on a separate sheet of paper and write in complete sentences!!
1. What quantities do you need to know in order to determine the amount of heat released by the lead sinker in
cooling to the final temperature?
2. What important assumption have you made in question 1 in determining the amount of heat released by the
lead sinker?
3. How is each quantity in question 1 obtained?
4. What quantities do you need to know in order to determine the heat capacity of the lead sinker?
5. How is each quantity in question 4 obtained?
6. How is the heat capacity determined?
7. If using a glass thermometer, why should it NOT be used as a stirring rod?
MATERIALS: Student will list all the materials needed in the procedure as a part of their pre-lab
PURPOSE: To determine the heat capacity of a lead sinker.
SAFETY: Wear goggles and apron. Use caution with burner.
PROCEDURE: Do not forget to highlight data and action terms as a part of your pre-lab.
1. Obtain two lead sinkers and find their combined mass. Record mass in Data Table
2. Attach a piece of thread to the eye of each sinker. The thread is to be used in moving the sinkers.
3. Heat to boiling about 100 mL of water in a 250 mL beaker. Carefully rest the sinkers in the boiling water
bath and leave them there for a minimum of 5 minutes. The thread should not be allowed to fall in the
beaker, nor should it drape over into the flame. Measure and record the temperature of the boiling water.
DO NOT ASSUME THE BOILING TEMPERATURE IS 100oC.
4. Place 65 mL of room temperature water in the calorimeter. Record the temperature. Keep the
thermometer in the calorimeter for the remainder of the lab exercise.
5. Carefully remove the sinkers from the boiling water bath and quickly place them into the water in the
calorimeter. Turn off the burner.
6. Gently stir the calorimeter water (use a stirring rod if using a glass thermometer) while continuously
observing the temperature change. Record the maximum (highest) temperature reached by the water in the
calorimeter.
LHS Honors Chemistry
Page 1
7. When the final temperature has been reached, clean up your lab station and return sinkers to your
teacher. Be sure to wash your hands.
DATA: student will create a data table for variables (with units) as a part of their pre-lab
CALCULATIONS: Respond to all questions on a separate sheet of paper. Write the formula for each question, show
all units, show all cancellations and BOX final answer!!
1. Determine the change in temperature of the water in the calorimeter.
2. Determine the heat absorbed by the 65.0 mL of water in the calorimeter in warming
to the final temperature (assume the water has a density of 1 g/mL: masswater = volumewater x
densitywater)
3. Determine the change in the temperature of the lead sinker in cooling to its final temperature.
4. Calculate the amount of heat released by the lead sinker for each one degree Celsius
change in temperature. This is the heat capacity of the sinker. Heat capacity = Qwater/ΔTsinker
ANALYSIS: Respond to all questions on a separate sheet of paper. Answer all questions in complete sentences and
you must show evidence/ explain using the concepts in chemistry and do some research!! Do not forget to reference
in text and have a reference page with correct APA citations.
1. What scientific law accounts for the assumption that the heat gained by the water is equal to the heat lost
by the lead sinkers? Explain thoroughly using chemistry concepts!
2. If you had a lead sample that was double the mass of the sinker you used in the lab, what would be the
heat capacity of the heavier sample? Give reasons for your answer including calculations to support your
answer. Explain thoroughly using chemistry concepts!
3. What is the relationship between the specific heat of a substance and the heat capacity of a sample of
that substance? Explain thoroughly using chemistry concepts.
4. Given the mass of your lead sample, calculate “c”, the specific heat of lead. Show formula, working and
units.
5. Determine the percent error for the specific heat calculated in question 4, if the accepted value for the
specific heat of lead is 0.129 J/g.oC. Show formula, working and units
6. The specific heat of most oils is about 2 J/g.oC, compared to a value of 4.18 J/g.oC for water. Why do you
suppose oil, rather than water, was the liquid of choice by castle defenders against invading forces? Show
formula, working and units when trying to explain through calculations. Do not forget to explain in words
after the calculations - using chemistry concepts and your data.
7. How does this lab experiment relate to REAL world application? Explain how this lab experiment relates
to:
a) Engineering: use a real world example and explain the connection.
b) Mathematics: use a real world example and explain the connection.
c) Everyday life: use a real world example in this century (please do not use the example provided in the
introduction paragraph) and explain the connection.
LHS Honors Chemistry
Page 2