3 Nature Of Heat

Becky McCoy

Title: NATURE of HEAT Timing: 50 minutes

Target Audience: High school Physics

Objectives Students Will Be Able To: • Describe how heat is related to thermal energy. • Relate specific heat to an object’s internal energy. • Observe, take data, and keep notes during an experimental activity. • Use equations to calculate an object/substance’s internal energy as well as the change in internal energy in an object/substance for a given temperature change. The Teacher Will Be Able To: • Provide students with opportunities to observe thermal energy transfer. • Assess student’s comprehension of different forms of heat transfer.

Standards Assessed: Advanced Placement (AP) Physics B Competency Goal #31 • Objective 3.02: Evaluate and investigate temperature and heat

Misconception(s) Addressed: •

The application of heat to a body always results in a rise in temperature.

Concept Map Vocabulary • • • • • • • • •

Heat – Energy transfer from an object/substance with a higher temperature to an object/substance with a lower temperature. Internal Energy – The energy in the system arising from the relative positions and interactions of its parts. Specific Heat – The energy transferred when 1kg of material is raised or lowered 1oCelsius. Heat Transfer – Process by which energy is passed between two different objects/substances; Types of heat transfer include: Radiation, Conduction, Convection, Diffusion Radiation – Energy transferred through electromagnetic waves. Conduction – Energy transferred through direct contact of two objects/substances. Convection – the transfer of heat by the circulation or movement of the heated parts of a liquid or gas. Diffusion – Intermingling of molecular parts due to change in thermal energy. Insulator – An object or material that minimizes the transfer of thermal energy.

Becky McCoy •

Conductor – An object or material that allows thermal energy to transfer easily.

Lesson Plan Aim: Collect information and data about thermal energy and heat transfer. Physics Push-Up: Think-Pair Share (5 min) Students should discuss with their partner what they discovered in class the day before. Were their predictions accurate? Do they agree whether or not gloves, hats, coats, etc. create heat?

Small Group Activity: Experiment Stations and Two Stay: One Stray2 (25 min) The class should be broken into groups of four or five so that there is an even number of groups. Half of the groups should start at STATION I, with enough stations for each group. The other half of the class should start at STATION II while the teacher guides the observation. When students are working at their group’s first station, they should check their results with the other groups (Two Stay: One Stray). After 10 minutes, the groups should switch to the other station. This leaves 5 minutes for clean up. Materials: • Butter • Spoons of different materials, such as plastic, wood, silver, and other metals. • Glass beakers • Glass flasks • Hot water • Balloons • Hot plates • Cold water in large container • Activity sheets Procedure: STATION I: Butter and Spoons • Place several spoons of different materials in a beaker without them touching each other. • Put a small pat of butter along the stem on each utensil at the same height. • Pour some hot water into the beaker up to a level below the butter; measure water temperature, and observe what happens. • Students will record what happened to the butter and if it happened to each spoon. Why did this happen? STATION II: An Inflating Balloon

Becky McCoy • • • • • • •

Fill a flask with 100 mL of water and a large beaker with 300mL cold water. Heat the flask over the Bunsen burner until hot. Measure the temperature of the hot water and the cold water. Seal the opening of the flask by securing a balloon on the lips of the flask. Have the students observe what happens to the balloon. Place the flask of hot water in a larger glass of cooled water and observe the reaction of the balloon. After 5 minutes, students should measure the temperature of the hot water flask and cold water beaker.

Teacher Talk: Equations (15 min) Introduce the relevant equations from the concept map. • E=CMGT (E is the amount of internal energy contained in an object at a given temperature.) • Heat=CMG∆T Explain to students that the heat equation uses the change in temperature (∆T ) because the energy transfer is due to the difference in temperature between objects. This is the opportunity to show students how to use the equations by doing a few examples. Example 1: Hot tea is poured into a glass mug. Find the total energy of the system. Mass of Tea: .25kg Specific Heat of Tea: 1.0Cal/deg/kg Temperature of Tea: 70oCelsius Mass of Glass: .10kg Specific Heat of Glass: .20 Cal/deg/kg Temperature of Glass: 70oCelsius Cal 1.0 x0.25kgxT = 0.25T = Energy tea deg· kg Cal 0.02 x0.10kgxT = 0.02T = Energy glass deg· kg E total = 0.25T + 0.02T = 0.27T = 0.27x70 = 18.9Calories (from "Introductory Physics" by Karplus) Example 2: How much heat must be added to 0.50kg of water at room temperature (20oC) to raise its temperature to 30oC? Mass of Water: 0.50kg Specific Heat of Water: 1.0 Cal/deg/kg Initial Temperature: 20oC Final Temperature: 30oC E = .50x1.0x(30 - 20) = 5Calories (from "An Introduction to Physical Science" by Shipman, Wilson, and Todd)

Becky McCoy

Homework: Hot Homework: Analyzing Data (2 min) Teacher announces that students should complete the Hot Homework: Analyzing Data Worksheet.

Exit Strategy: Activity Sheet Review (3 min) As students leave, the teacher should check their experimental worksheets to make sure they have their data recorded that they’ll need for their homework

Assessment: •

Formative: o Teacher plans to collect and review students’ activity sheets where they record their observations as well as Hot Homework the next day. o Student reactions during balloon activity.

References: 1 2

- http://www.ncpublicschools.org/curriculum/science/scos/2004/33apphysicsb - Group activity found online, written by: Sally Ferrelle, Oglethorpe Academy, Savannah, GA

Becky McCoy

Experimental Observations: Station I: Butter and Spoons Materials: •

Various Spoons of Different Materials o Spoon 1 Material: o Spoon 2 Material: o Spoon 3 Material: o Spoon 4 Material:

•

Butter

•

Beaker

•

Hot Water

Procedure: Write in your procedure here.

Observations: What did you observe after each procedural step? Is it what you thought would happen? Include your measurement of the hot water temperature. Note what types of heat transfer are occurring.

Becky McCoy

Experimental Observations: Station II: An Inflating Balloon

Materials: Glass flasks, balloons, hot plates, water, beakers.

Observations: What did we see? Why do you think we saw this?

Procedure: What did we do?

Measurements: Initial Temperature of Hot Water –

Final Temperature of Hot Water –

Initial Temperature of Cold Water –

Final Temperature of Cold Water –

Becky McCoy Name __________________________________________________ Date ________________

Hot Homework: Analyzing Data PART ONE: STATION I Butter and Spoons Find the temperature change of each spoon using the room temperature, specific heat of specific materials, and temperature of the water. Specific Heat: measured in kcal/kg*Celsius Water – 1.00 Wood – 0.40 Steel – 0.12 Plastic – 0.40 Rubber – 0.48

Room Temperature = 21oC Temperature of Hot Water = Equations: E=CMGT Heat=CMG∆T

Becky McCoy

PART TWO: STATION II An Inflating Balloon Using the data you collected, find the energy involved in cooling the hot water and warming the cold water.

EXTRA CREDIT: Calculate how much energy would be involved to bring the hot and cold water to the same temperature. How long would it take?