Heat and Temperature: Is There a Difference?

Sample Lesson for Grades 3-8

Dennis W. Sunal

The University of Alabama

Tuscaloosa, Alabama

Alternative Conception Addressed by the Lesson Plan: Heat and temperature are the same thing.

Lesson Goal: To allow students to investigate, develop inferences, and differentiate between the concepts heat and temperature.

Prerequisites: Can measure temperature to the nearest two degrees with a thermometer.

Exploration

Objective: The students will investigate mixing hot and cold water by making predictions of the resulting mixture accompanied with observations of the results.

Materials: For each group:

Two styrofoam cups per group

A source of hot water (from a tap or hot plate at about 50 Celsius or 122 degrees Fahrenheit)

Cold water with floating ice cubes in it (with a temperature of about 0 degrees Celsius or 32 degrees Fahrenheit)

One thermometer per group

Paper towels

Paper to make a bar graph and for recording

results

One kitchen measuring cup with metric or English measures

Procedure:

A. Place the students in groups of four and assign roles: materials manager, readers/observers (two students), and recorder.

B. Describe materials and instructions needed for student groups to carry out the activity of mixing various temperatures and quantities of water.

C. State the key questions: "What happens when we mix together two water samples that have different temperatures?" "Can you find a way to guess, or predict, what the temperature will be when you mix together two water samples that have different temperatures, one that is warmer with one that is colder?"

D. Letís start with a thought problem. Discuss it in your groups. Decide on an answer and write it down. Then begin your group activity. Here is the problem: if you mix one-fourth cup of very hot water with three-fourths cup of very cold water, what will be the temperature of the mixed water? Write down your prediction..

E. Ask the groups to do the activity explained above in number one of Discrepant Activities in Heat and write down what they find. The data could be recorded in a bar graph or data table.

F. Ask each group to discuss the results of Activity E and the questions from Activity C above.

Evaluation: Each group of students will have completed all predictions for the Exploration activities. Their predictions should be evaluated for prior knowledge and monitor their participation as a group by observing whether groups stay together while working and each person has a chance to share their ideas.

Invention

Objective: The students will investigate properties of heat and materials and determine that the heat energy possessed by an object is related to both the quantity of matter present and its temperature.

Materials: For each group:

Eight clear plastic drink cups

A source of hot water (from a tap or hot plate)

Crushed ice (do not use ice cubes)

Paper towels

Paper to make a graph and for recording

results

One kitchen measuring cup with metric or English measures

Teaspoon

Procedure:

A. Place the students in groups of four as was done in the exploration.

B. Ask the students to report the results of their exploration activities. Help students communicate the results of their activities using tables and/or bar graphs to justify their conclusions. Continuously help students compare the results of one group with another.

C. Write the following questions on the board and ask the groups to discuss them. What can you decide about mixing two equal samples of water that have different temperatures? What can you decide about mixing a very small amount of water at one temperature with a lot of water at another temperature? What is more important, the temperature of the water with which you started or how much water you started with?

While the students are reporting their results, at appropriate points discuss an alternative way of looking at the properties of heat and temperature as a means of describing matter. The students can be expected to have some difficulties at this point because their preconceptions create a barrier to understanding that both properties, the original temperature and the volume of the water involved, are important and real. The amount of water at a specific temperature is related to the amount of heat internal energy present. Temperature relates only to how fast the molecules of water move (the energy of a single molecule) which causes the thermometer column to expand and rise. It may that single molecules have a large amount of heat energy but if there are not a lot of molecules there will not be a lot of heat in the entire sample.

D. Provide each group with a set of instructions on paper or three by five inch index cards. This activity will relate the concept of heat to the amount of internal energy that various quantities of water possess. Ask students to put together different amounts of hot water with the same amount of crushed ice. Mix one-fourth cup of crushed ice with three-fourths cup of hot water. Repeat the activity by mixing one-fourth cup of crushed ice with different amounts of hot water. Put one-half cup of hot water, one-fourth cup of hot water, and one teaspoon of hot water in separate cups.

To begin the activity, the students should place one-fourth cup of crushed ice in each of five clear plastic drink cups. Then they should measure out the four different amounts of hot water into other cups. Finally, they should quickly pour the hot water out of one cup into a paired crushed ice cup. They should repeat the process as fast as possible with all the other cups of hot water. The groups should make observations of all five mixtures for five minutes. At the end of five minutes they should be asked to note how much crushed ice is left in each of the five cups. Finally, they should relate the amount of crushed ice left in a cup to the amount of hot water (heat) added to the cup. Older students can perform a second activity by adding the same amount of water, three-fourths cup, at different temperatures to the crushed ice. Similar results will be observed.

E. Ask the students to record the results of their activity. At the end of each group report, the teacher should ask that group why different amounts of ice were found in the five cups at the end of the five minute observation period. The groups should also be asked to state the evidence by which they made their inference. At this point the students may report that the amount of ice left is related to the amount of water added to the cup. The teacher should explain that the added water was all at the same temperature. The temperature did not vary. Only the amount of water varied. Everything else was the same. If more hot water was added to the ice it was the same as adding more heat to the ice, which caused the ice to melt. Help the students focus on the smallest amount, a teaspoonful, of water added to the ice. Even though that water had a high temperature, it did not melt much ice. So, very little heat was added to the ice.

F. As a closure, explain to the students that heat and temperature are two different properties of materials. Temperature is measured with a thermometer. It indicates the amount of quickness of motion or speed energy each particle of water has. An increase in speed causes matter to expand, so liquids will rise in a thermometer. Heat energy can be measured by its effect on the amount of ice it can melt. This is a practical way of measuring heat energy. Heat is a measure of how much energy all the particles in an object have lost or gained. It indicates the total amount of internal energy transferred to or from a specific amount of water.

Evaluation: When asked during the Invention to make an inference about the ice and water, the group reports the evidence upon which the inference was made. The evidence should relate in a logical way to the inference. Group participation will be assessed by noting whether all members were part of the plan and had a chance to do their part.

Expansion

Objective: The students will solve everyday problems involving the properties of heat and temperature.

Materials:

Ten clear plastic drink cups

Crushed ice

Paper towels

Paper for recording

results

One kitchen measuring cup with metric or English measures

A source of hot water (from a tap or hot plate at about 120 degrees Celsius)

Cold water with floating ice cubes in it (with a temperature of about 0 degrees Celsius or 32 degrees Fahrenheit

Thermometers

Tablespoons

Procedure:

A. Place the students in groups of four and assign roles: materials manager, readers/observers (two students), and recorder.

B. At stations set up around the room, the groups will be asked to solve a variety of problems.

Station 1. Ask students to take one-half cup of very cold water and predict the final temperature when one-half cup of hot water is added to it.

Next, ask them to follow these directions. Get one of each sample. Measure the temperature of each cup of water. Then, pour the hot water into the cold water cup. After thirty seconds, take a measurement of the temperature of the mixed cup of water and compare it to their prediction. (The students should find a temperature midway between the temperatures of the starting cups of water.)

Station 2. Present the following problem.

Mom is having a cup of coffee after dinner. She pours almost a full cup of coffee. The temperature of the coffee is about 120o Fahrenheit (F). She adds one tablespoonful of cold milk to the coffee. What temperature is her coffee now? Write your prediction on a sheet of paper. Describe the reasoning behind your answer.

Next, ask them to follow these directions. Get one cup almost full of hot water, a second cup one-fourth full of cold water, and one tablespoon. Measure and record the temperature of the hot water and of the cold water. Pour one tablespoon of cold water into the hot water cup. Measure and record of the temperature of the mixed cup of water and compare it to their prediction. (The students should find a temperature that is still warm, perhaps 105 degrees Fahrenheit.)

Station 3. Present the following problem.

You are having hot chicken soup for dinner. Mom always serves it too hot for you to eat, about 120o F You are really hungry so you do not want to wait for it to cool down. You want to eat it right away. So, you are going to add some very cold water to it. There is about one cup of soup in your bowl. How much very cold water should you add to your soup so that its temperature will be below 90 degrees Fahrenheit? Write your prediction on a sheet of paper. Describe the reasoning behind your answer.

Next, ask students to follow these directions. Try out your guess using the hot water, cups, and thermometer at this station. If your guess didnít work, measure out more or less water until you get it to about 90 degrees. Record all work. (The students will need to measure out about one-third of a cup of very cold water.)

Teacher Note: The following three stations may be discussed without performing the task. If time is available, the teacher may wish to have the students carry out the activity at the station or one group of students could demonstrate the stationís activity to the whole class.

Station 4. Present the following problem.

Which will have a higher temperature after one minute on a burner: a small pot with one cup of water in it or a small pot with one-fourth cup of water in it? Write your prediction on a sheet of paper. Describe the reasoning behind your answer.

(For every degree of temperature increase, the larger amount of water requires more heat than does the smaller volume of water. Since the burner is giving off the same amount of heat during every one-minute period, the larger amount of water will rise to a lower temperature when compared to the smaller amount of water.)

Station 5. Present the following problem.

Which will cool to the lower temperature in ten minutes: a plastic glass containing one cup of very hot of water or a plastic glass containing one-fourth cup of very hot water?

(The larger amount of water has more heat and therefore takes longer to cool down.)

Station 6. Present the following problem.

Which has a higher temperature: a cup of boiling hot water or a swimming pool of water at air temperature? Which has more heat: a cup of boiling hot water or a swimming pool at air temperature?

(The cup of water has the higher temperature. The swimming pool has more heat. If the students are having difficulty with this question, ask them "Which can melt more ice: A cup of boiling hot water or swimming pool of water at air temperature?" "Which had more heat?" )

C. Discuss the results of their station activities in a whole group. The teacher can summarize their ideas on the board.

D. Summarize the lesson by stating that when we started the activities, the students may not have been able to tell the difference between the words "heat" and "temperature." By mixing different amounts of water and by melting ice with different amounts of water, they should be able to apply the terms "heat" and "temperature" to their everyday lives. Whether they are talking about soup or coffee they should be able to use the idea of heat to guess how long it will take things to heat or cool. They should also be able to guess how much cool water they need to mix into hotter water to make it cool.

Evaluation: Tell the following story to the students.

Juan had a carton of cold milk sitting on his lunch tray. Jill came by and said that she did not like the soup that came with lunch. It was steaming and looked like it was too hot to eat. She took a tablespoonful of her hot soup and poured it into Juanís milk. After yelling at Jill to "Stop it!" Juan decided to drink his milk even though there was some soup in it. He was surprised to find out that his milk was still cold.

Write down your ideas about whether or not Juan should have been surprised that his milk was still cold.