5 What is heat? — Heat vs. temperature

This lesson introduces students to thermochemistry by allowing them to discover the difference between heat and temperature, and ultimately the specific heat of various substances. The students will work with samples of wood, metal, and plastic in order to make these discoveries. Students conclude the lesson by defining heat, temperature, and specific heat.

Learning outcomes

Students will:

• distinguish between temperature and heat
• compare the temperature changes and heat absorbed by three different solids
• understand and predict how a substance’s temperature will change as heat is added, based on the specific heat of the substance
• explain specific heat and describe how it differs from substance to substance
• calculate an unknown using q = mCΔT

Teacher planning

Time required

1.5 class periods (85 minutes each)

Materials needed

• “Heat vs. Temperature” student sheet (1 per student)
• samples of wood, metal, and plastic (8 sets)
• 8 thermometers
• calorimetry activity sheet (1 at each of the 8 lab stations)
• 8 calorimeters (This may be as simple as 2 styrofoam coffee cups inside each other and a lid made from a piece of cardboard.)
• hot plates (4 shared between lab stations)
• optional: “Chemistry and Energy” PowerPoint presentation

Pre-activities

• Student desks should be arranged so they can easily work in groups of three or four.

Activities

1. Prior to class, place a sample of wood, metal, and plastic on the desk for each group of students.
2. Have students brainstorm places where they encounter energy in their daily lives.
3. Hand out the “Heat vs. Temperature” student sheet.
4. Ask students to read the objectives and perform steps 1 and 2 of the activity, in which students are asked to arrange the samples of wood, plastic, and metal in order from coolest to hottest, and then have the teacher check the order.
5. As the students work, rotate from group to group and check the order of their samples. You may initial their sheets.
6. As you check the order for each group, hand out thermometers and ask the groups to record the temperature of each substance in Table 1 on the student sheet.
7. Have students continue with steps 3-5 on the student sheet, which have students record the temperatures of the samples and of the room, and then predict what might happen to the temperatures of the samples if they were placed in a boiling water bath for two minutes. Initial step 5 when students have completed their predictions.
8. After ensuring that step 5 has been completed, have students go to the lab and perform the calorimetry activity as described on the calorimetry activity sheet. When using this activity, it may useful for the teacher to know approximate specific heats of wood, plastic, and metal. It is easy to look these up using the internet, but some examples are included for your use. It’s important to note, though, that these vary depending on the specific wood, plastic, or metal, and are included only as a general guide:
   • Cpine wood = 2.5 J/g°C
   • Cplastic = 1.67 J/g°C
   • Cmetal = 0.5 J/g°C
9. When students return to their seats, present notes about heat, specific heat, and q = mCΔT problems. You may use the “Chemistry and Energy” PowerPoint found in the materials list.
10. Have students complete Data Table 2 and steps 7-13 of the student sheet as they proceed through this activity. (Questions 7-9 ask students about their observations of change in temperature during the calorimetry activity. Questions 10-12 ask students about the definitions of and differences between heat and temperature. Question 13 defines specific heat and asks students to arrange the three samples from lowest to highest specific heat.)
11. It may be necessary to stop the class around step 11 to ensure that students are able to make a distinction between heat and temperature. If students are getting the idea, allow them continue through step 13.
12. Provide the specific heat of water (4.184 J/g°C or 1 cal/g°C) so students may enter it on the activity sheets after step 13. Most metals have specific heats of less than 1 J/g°C. Lead a discussion that lets students understand that substances with higher specific heats will take longer to acquire heat and change temperature and they will also hold on the heat longer. Here again, the “Chemistry and Energy” PowerPoint may be useful.
13. Ask each group to write a list of things they have learned so far. Call on a volunteer from each group to state one thing they learned that has not been mentioned.
14. Assign questions 1-8 on the post-activity questions sheet (on the “Heat vs. Temperature” student sheet) for homework.

Assessment

The following may be used for assessment:

• student feedback after step 13 of the activity.
• students’ completion of the post-activity questions
• students’ use of these concepts throughout the unit after this lesson
• unit test

Critical vocabulary

temperature

a property directly proportional to the kinetic energy of a substance. Temperature is measured using a thermometer and has units of K, °C or °F. Temperature is represented by the symbol ΔT or T. ΔT is calculated as Tfinal - Tinitial.

heat

a transfer of energy between two objects due to a difference in temperature. Heat always moves from hot to cold. It has units of Joules, calories or Calories (kcal). The symbols used for heat are ΔH or q. Heat is not directly measurable. It must be calculated using the formula q = mCΔT.

specific heat (C)

the amount of heat it takes to raise the temperature of 1 g of a substance 1°C. The symbol for specific heat is C. It has units of joules / g °C or calories / g °C. Every substance has its own unique specific heat that can be found in reference books. The formula used to determine the specific heat of an unknown is C = q / mΔT.

heat capacity

the amount of heat necessary to increase the temperature of an object exactly 1°C.

• Next: Units of heat: How much energy is that anyway?

National Standards

In addition to meeting objectives of the North Carolina Standard Course of Study, this lesson plan addresses the following national standards:

National Science Content Standard A

As a result of their activities in grades 9-12, all students should develop an understanding of:

• Abilities necessary to do scientific inquiry
• Understandings about scientific inquiry

National Science Content Standard B

As a result of their activities in grades 9-12, all students should develop an understanding of:

• Structure and properties of matter
• Conservation of energy and increase in disorder

• Next: Units of heat: How much energy is that anyway?
• Previous: Reaction stoichiometry: How can we make chalk?

Author’s note

This activity is written for honors chemistry students. In order to use it for academic chemistry students, you may have to stop more often and review key concepts with the students.

Supplies

For the samples of wood, plastic, and metal, you can use density kits purchased from Fisher Scientific.

Learn more

Related topics

• Search LEARN NC for more resources on chemistry, hands-on, heat, labs, science, temperature, and thermochemistry.