Investigation of Heat capacity and Specific Heat: Using Different Temperatures of Water and Solids

Kristin Cuta, Minnesota North Star Academy, St. Paul, MN, based on an original activity from the USAFA Chemistry Department and http://www.science-projects.com/HeatCapacity.htm.
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Summary

In a lab-based chemistry class, students will investigate the topic of specific heat and heat capacity using different temperatures of water and solids. Students will collect information based on observations and apply the mathematical equations of specific heat and heat capacity to their data. Students will write a lab report in their laboratory notebooks describing their experiment and results. The procedure for the lab is provided below. As a final assessment, students will do a problem-solving lab based on real-life situations using a water heater, also writing a lab report on their procedure, recording their thought process. The goal of this activity is to promote critical thinking skills and improve data analysis.

Learning Goals

Higher order thinking skills:
1) Data analysis
2) Synthesis of ideas
3) Critical thinking
4) Observation and laboratory skills
Concepts covered:
1) Demonstrate the law of conservation of energy
2) Understanding heat capacity and specific heat concepts
Vocabulary words:
1) Heat capacity
2) Specific heat

Context for Use

-This activity will be used at a high school deaf/hard-of-hearing charter school, students in grades 10 to 12.
-Monday through Thursday, the chemistry class is only in 50 minute periods. Every other Friday, class occurs in an 80-minute block. The class does not meet every Friday.
-Classroom is small, as it is being shared with the language arts teacher, so this needs to be taken in consideration during lab activities.
-Lesson will be adapted to match individual student needs. Some students will answer more questions than others, accommodations made at teacher discretion.
To help students understand the experiment, teacher will go through experiment showing the equipment, briefly describing each step. The lessons are taught using American Sign Language, SmartBoard for written English language and visual information, and use of writing in laboratory notebooks.
-Lesson can be used for any level, with more difficult tasks or questions added to the lesson. Modification can occur with simplifying the lab steps with pictures/less words, and having students answer a few key questions.
-This activity will take several days (possibly a week) with the "Heat Capacity" lab used first to introduce the concept of heat flow from warm to cold water and to learn how much heat (calories) it takes to heat up a gram of the specified material.
-The final activity is used to assess student understanding of heat capacity and specific heat, wrapping up the topic of heat capacity and specific heat.
- Some deaf and hard of hearing students will need pre-teaching on water heaters, what they do and what they look like. Visuals and a discussion needs to take place before students do the final assessment activity.

Subject: Chemistry:General Chemistry:Thermodynamics:Heat
Resource Type: Activities:Lab Activity
Grade Level: High School (9-12)

Description and Teaching Materials

Students will be introduced to the concept of heat capacity and specific heat after they have already been taught and/or exposed to the concept of chemical reactions, endothermic/exothermic reactions, and the law of conservation of energy. The purpose is for the students to understand the transfer of heat from one location to another and that the specific heat of water does not change, regardless of temperature. The introduction of the lesson will start with a question, drawing out information from students' prior knowledge. The students will discuss why a lake or an outdoor swimming pool becomes cooler in the morning, despite being warmer the day before in the afternoon or evening. They will discuss with partners, journal their ideas, and then share with the entire class. Once this occurs, students will be taught concepts related to specific heat and heat capacity. They will learn the terminology, reminded of law of conservation of heat and exothermic/endothermic reactions. After learning the topic, they will do the activity "Heat Capacity," using materials listed below. Procedure is also included.

Activity is found from website:
http://www.science-projects.com/HeatCapacity.htm

-The following link provides information on a teacher page to explain how to open up the class to the discussion of heat capacity:
http://www.science-projects.com/HeatCapacityT2.htm
http://www.science-projects.com/HeatCapacityT.htm#speedier - The link directs to a teacher page on how to measure heat capacity, if guidance is needed.

Materials:
-3 buckets
-Styrofoam cup
-2 Thermometers
-Ice
-Mass balance
-Metals (if you want to add solids to water)
Lead (fishing or drapery weights)
-Iron (nails, screws, bolts, wire, hammerheads)
-Aluminum (spool of wire)
-Copper (spool of wire)
-Brass (copper/zinc: bells, spool of wire, screws)
-Bronze (copper/tin: pennies)
-Glass (marbles, small bottles)
-Water
-Ice
-Ethanol
-Plastic
-Piece of candle wax
-Pound of feathers

Procedure:
-The day before the lab takes place, place two full buckets to stand overnight to reach room temperature.
-Just before doing the experiments, fill a third bucket with water and ice, and into the ice water add all the other components the instructor provides with any liquids in their bottles. Allow all to come to thermal equilibrium in the ice/water.
First trial
1. Using water from one of the room temperature buckets, fill a Styrofoam cup half way, with its mass already recorded prior to filling up the cup. Carefully measure the temperature of the water in the cup, being precise as possible.
2. Place the cup on a balance, and note the mass, and also determine the mass of water in it.
3. With minimum contact, think about why you would do this, remove a little of the ice-water, without getting any of the ice chunks, and pour it into the cup of water, and stir.
4. Note the mass in the cup, and determine the mass of the cold water added.
5. Measure the temperature of the water after it has come to thermal equilibrium.
6. Using this calculate: |(Δtemp original water x mass of original water)/(Δtemp ice water x mass of ice water)| = the RELATIVE heat capacity of the cold water you added.
7. Find specific heat of the water using formula: q=cmΔT.
"|" is the symbol for "absolute" value, which means making a negative number positive. This is your control. If your answer is close to 1.0, you are doing the procedure correctly.

Other trials:
Suggested things to test:
-Metals (if you want to add solids to water)
Lead (fishing or drapery weights)
-Iron (nails, screws, bolts, wire, hammerheads)
-Aluminum (spool of wire)
-Copper (spool of wire)
-Brass (copper/zinc: bells, spool of wire, screws)
-Bronze (copper/tin: pennies)
-Glass (marbles, small bottles)
-Water
-Ice
-Ethanol
-Plastic
-Piece of candle wax
-Pound of feathers

1. Test the various other solids available to you.
2. Test the liquids in the bottles. To do this, just pour some out of the chilled bottles into the water in the cups. And don't forget to test the cold water itself!
3. Test an ice cube, while you have some in the ice-bath.

Conclusion:
1) Why was minimum contact with ice-water needed in the first trial?
2) What did you notice about the water temperature before and after you added the ice-water? Explain how you think this occurred.
3) When you added solids to water, what did you notice about the water temperature?
4) Using terminology learned in this class (heat capacity, specific heat, law of conservation of energy), write a paragraph conclusion about your observations and what you have learned in this experiment. Include any questions that were generated during the experiments and what you may possibly do to change the experiment if you did this again.

Final Lab Activity:

-Used as an Assessment-Obtained from Mini-Lab: In Hot Water
NOTE: Before you start this activity, take your thermometer and cover it with aluminum foil so you can only read from 0 - 40 degrees Celsius.
You've just taken a class on energy conservation and you want to do your part. You realize that you can save a lot of energy (and even some money) by turning your water heater down to between 50 and 55 ºC. However, your water heater doesn't have a calibrated control (most don't) and, to make matters worse, your thermometer only reads up to 40 ºC!
a. Collect some hot water from the tap (as hot as possible) - it should be well above 40 ºC. Use your knowledge of heat flow to determine the temperature of the hot water.
b. What's your major source of error in this experiment?
c. Describe at least one way that you could improve the accuracy of your temperature determination.

WAIT! Do not write down an answer to the Final question until your Instructor tells you to.
d. FINAL: Explain the principles and assumptions you used to determine the temperature of the water."
Lab from: Mini-Lab 9: In Hot Water (from United States Air Force Department of Chemistry) attached in its original form. (Parts of the Mini-lab copied above). Final assessment handout (Microsoft Word 85kB Sep11 08)

Teaching Notes and Tips

Reinforce ideas related to law of conservation of energy and exothermic/endothermic reactions, go through typical safety guidelines expected in the lab, give practical tips or hints to students who may struggle with concepts, expound on lab steps as needed matching student needs, or have students read the lab activity independently, based on their level of comprehension.
I have not been able to have time to use these labs in the past, but my goal is to use this activity after covering chemical changes and energy in class.
For the final lab activity, thermometers are needed that only read to 40 ºC or cover them up that only up to 40 ºC can be read.
These are a few tints to give students, which are a few basic assumptions that can used in determining the temperature of the water:
- Zero heat loss, meaning that the heat that flows from the hot water all goes into the cold water.
- The specific heat of the hot water is the same as that of the cold water, and they're
both equal to the specific heat of pure water: 4.184 J/gºC.
This lab assessment hopefully allows students to gather data and generate answers to questions they may have. This activity should help students feel value of data collection and recording observations when they are attempting to answer, and create questions based on their data collection and observations.

Assessment

Students will need to create a lab report for the "Heat Capacity" lab, using their laboratory notebooks. They will be graded on components needed for the lab notebook such as title of lab, lab purpose (question to answer), materials needed for experiment, procedure that was followed, data collection, and conclusion to the lab. Teacher will lead students in a discussion and provide them with more background information after the lab, re-iterating information that should have been taught prior to the lab in a lecture/presentation form. After the lab, emphasis is made on topics now the students have been exposed to the activity. To assess final understanding the Mini-Lab "In Hot Water" will be used, with students working in pairs to problem-solve, using the knowledge they have obtained from the "Heat Capacity" lab. This final assessment will be graded based on student lab reports, which includes title, purpose of the lab, materials used, procedure that was followed to obtain data, data collection, and conclusion. Students will answer the questions provided in the Mini-Lab.

Standards

IIC 1. The student will know that potential energy is stored energy and associated with gravitational or electrical force, mechanical position or chemical composition.
IIC 5. The student will be able to describe physical and chemical changes in terms of the law of conservation of energy.

References and Resources