Calorimetry�Measuring Heat Energy Transfer

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					                    Calorimetry—Measuring Heat Energy Transfer
Subject Area: Chemistry
Grade Level: High School Chemistry
Lesson Title: Calorimetry—Measuring Heat Energy Transfer

National Science Education Standards:
    Science as Inquiry: 9–12
    Science as Inquiry: Abilities to Do Scientific Inquiry, 9–12
    Science as Inquiry: Understanding About Scientific Inquiry, 9–12
Physical Science Standards:
    Structure and Properties of Matter: 9–12
    Conservation of Energy and the Increase in Disorder: 9–12
    Chemical Reactions: 9–12
Life Science Standards:
    Matter, Energy, and Organization in Living Systems: 9–12

Suggested Prior Knowledge: heat and energy, energy changes and conservation, internal
energy and the first law of thermodynamics, energy, enthalpy

Purpose: To conduct a class-designed experiment that will demonstrate the measurement of heat
transfer from one substance to another

Key Vocabulary:

    heat—the energy transferred between two objects as a result of a temperature difference

    heat transfer—the transfer of thermal energy between two bodies due to a difference in
    their temperatures

    internal energy—the energy in a system, stored at the molecular level

    kinetic energy—the energy of motion; EK = (1/2)mv2

    law of conservation of energy—the first law of thermodynamics; states that energy cannot
    be created or destroyed, and that the total energy of an isolated system must therefore
    remain constant

    specific heat—the amount of heat required per unit mass to raise the temperature of a
    substance one degree

Calorimetry—Measuring Heat Energy Transfer (High School Level)                                 1
    system thermal energy—The kinetic energy of the particles plus the potential energy stored
    within the atomic bonds of a system

    temperature—a measure of the kinetic energy of molecular motion

    thermal equilibrium—when the temperature of two interacting bodies become equal

Objective:
  1. Students will understand the relationships between energy, temperature, and heat.
  2. Students will be able to measure energy transfer from one substance to another using a
      calorimeter.
  3. Through facilitated deliberation, students will design a procedure for conducting the lab
      and data collection.

Materials (each group should receive the following):
- student worksheet
- calorimeter or strong foam container with lid
- formal lab clothing, including goggles, with lab safety protocols required
- aluminum 10–50 grams (shot or hardware fitting)
- iron 10–50 grams (shot, wire, or pipe fitting)
- copper 10–50 grams (shot, wire, or pipe fitting)
- thermometer
- stirring rod
- matches
- paper clip
- scale capable of measuring tenths of a gram
- hot plate
- tongs
- heat-proof gloves
- graduated cylinder
- 100 ml beaker

Procedure:
1. Refresh concept knowledge in a discussion about energy with the class by asking students the
following questions:
     What does temperature measure?
     What is heat?
     How does energy differ between a cup of water and a bath tub of water at the same
        temperature?
     What variables do we need to account for when transferring heat from one object to
        another?

2. Use the discussions and conclusions from the above conversation as an introduction to a class-
designed experiment that determines the thermal energy transfer in a classic calorimetry
experiment.

Calorimetry—Measuring Heat Energy Transfer (High School Level)                                    2
3. State the challenge to the class. All lab groups will be given a variety of metals which they
will heat up and then transfer the energy absorbed by each metal to an alternate substance. Some
questions to initiate the thought process include the following:
     How will you conduct the experiment?
     What data will need to be collected?
     What variables will you consider and account for?
     What safety concerns do we have?
     What supplies do you need?
     Do you have a hypothesis that includes terms from the key vocabulary list?

4. Help students along by interjecting the terms of the thermal energy formula and other key
mathematical conversions as appropriate, such as:
     change in thermal energy (Q) = mass × change in temperature × specific heat (Cp); Q =
       mCp∆T
     1 calorie = 4.18400 joules
     1 Kilogram = 1000 grams (specific heat calculations use kilograms, and data collections
       should reflect the same)

5. Once a class procedure has been designed and the key vocabulary has been introduced, the
experimental procedure should include and resemble the following steps:
     record the mass of the metallic samples you will use in your experiment
     place your metal samples in a beaker, add enough water to cover the samples and bring
       the contents to 100°C
     record a desired volume (75–125 ml) of cool tap water (5 °C) of water and add it to the
       calorimeter
     record the initial temperature of the water in your calorimeter
     using tongs carefully remove the samples from the hot water and place all of them into
       the calorimeter (testing each sample individually would be a valid procedure as well)
     record the final temperature (peak temperature)
     use the thermal energy equation and the specific heat chart to calculate the change in
       thermal energy

4. Review with students the idea of how much energy the different materials were able to hold.
Discuss with students which materials hold heat the most or least and how this may apply to
materials science and modern industries.

5. Finally have students make decisions as to where error may have been introduced in the lab.
The energy absorbed by the calorimeter and energy lost to the environment are common
considerations but usually not included at this level of study.

Additional Resources:
   http://www.watchknow.org/Video.aspx?VideoID=17223
   http://www.chemistryexplained.com/Ge-Hy/Heat.html
   http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/spht.html

Calorimetry—Measuring Heat Energy Transfer (High School Level)                                   3
Extensions:
1. Student Research
Students may want to connect this experiment to the real world by further experimentation or
research related to foods and their caloric content; the need for high caloric foods for athletes and
developing children versus adults; materials for vehicles, including materials used in engines,
motors, etc. to dissipate heat; space shuttle tiles, and so on. Students may want to produce a
product of their research results, such as a traditional research paper, a review of relevant
research, a PowerPoint presentation, or find appropriate videos or make their own videos.

2. Calculating Molar Heat Capacity
Background:
Molar Heat Capacity (Cn) of a substance is the amount of heat required to raise the temperature
of 1 mole of the substance by 1oC (or by 1 K). The units of molar heat capacity are J oC-1 mol-1
or J K-1 mol-1

Use the following formula to calculate molar heat capacity: q = n x Cn x (Tf - Ti)

q = n x Cn x (Tf - Ti)
q = amount of heat energy gained or lost by substance
n = moles of substance
Cn = molar heat capacity (J oC-1 mol-1 or J K-1 mol-1)
Tf = final temperature
Ti = initial temperature

Student Challenge:
Using the information above have students calculate the molar heat capacity of the metals used
in this lab. Have students draw a conclusion about the relationship between metals and their
molar heat capacity.

Conclusion:

______________________________________________________________________________

______________________________________________________________________________


Answer: the molar heat capacities of most metals around room temperature are all around 25
J/K.g. This is because the capacity to accommodate energy depends on the number of metal
atoms.

Resources for Possible Extensions:
    http://www.sciencebuddies.org/science-fair-projects/project_ideas/FoodSci_p012.shtml
    http://www.livestrong.com/article/359653-how-to-calculate-calories-with-calorimeter/
    http://www.fire.nist.gov/bfrlpubs/fire07/PDF/f07062.pdf

Practice Questions:

Calorimetry—Measuring Heat Energy Transfer (High School Level)                                     4
      How much heat is absorbed when 500.0 g of water goes from 25.0°C to 35.0°C? 20,920 J
      How much heat is absorbed when 500.0 g of copper goes from 25.0°C to 35°C? 1,930 J




Calorimetry—Measuring Heat Energy Transfer (High School Level)                            5
             Student Worksheet for Calorimetry—Measuring Heat Energy Transfer


Experiment Title: ________________________________ Date: ________ Name: _______



Develop a guiding question or questions for your experiment:

___________________________________________________________________________


Materials:

___________________________________________________________________________


Procedure:


____________________________________________________________________________


____________________________________________________________________________


____________________________________________________________________________


____________________________________________________________________________


____________________________________________________________________________


____________________________________________________________________________


____________________________________________________________________________




Calorimetry—Measuring Heat Energy Transfer (High School Level)                    6
Data:

                                                                 Specific Heat
 Sample ID       Sample Mass              Ti           Tf                                Q
                                                                     (Cp)




Chart of Specific Heats:




What are some possible sources of error in this lab, and how did you account for them?


______________________________________________________________________________


Conclusion (use the back if necessary):


______________________________________________________________________________


______________________________________________________________________________


______________________________________________________________________________

Calorimetry—Measuring Heat Energy Transfer (High School Level)                               7

				
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