Thermal Energy Transfer (Julie McLemore)

Title: Thermal Energy Transfer

Principle(s) Investigated: Energy, Thermal energy, Kinetic energy, Types of Thermal energy Transfer, Conduction, Convection, and Radiation

Standards:

Performance Expectations:

MS-PS3-3 Apply scientific principals to design, construct, and test a device that either minimizes or maximizes thermal energy

transfer.

MS-PS3-4 Plan an investigation to determine the relationships among the energy transferred, the type of matter, the mass, and the change in the average kinetic energy of the particles as measured by the temperature of the sample.

MS-PS3-5 Construct, use, and present arguments to support the claim that when the kinetic energy of an object changes, energy is transferred to or from the object.

Disciplinary Core Ideas:

PS3.A: Definitions of Energy

• Temperature is a measure of the average kinetic energy of particles of matter. The relationship between the temperature and the total energy of a system depends on the types, states, and amounts of matter present (MS-PS3-3, MS-PS3-4)

Science and Engineering Practices:

Planning and Carrying Out Investigations

• Plan an investigation individually and collaboratively, and in the design; identify independent and dependent variables and controls, what tools are needed to do the gathering, how measurements will be recorded, and how many data are needed to support a claim. (MS-PS3-4)

Engaging in Argument from Evidence

• Construct, use, and present oral and written arguments supported by empirical evidence and scientific reasoning to support or refute an explanation or a model for a phenomenon. (MS-PS3-5)

Crosscutting Concepts:

Energy and Matter

• The transfer of energy can be tracked as energy flows through a designed or natural system. (MS-PS3-3)
• Energy may take different forms (e.g., energy in fields, thermal energy, energy of motion). (MS-PS3-5)

Systems and System Models

• Models can be used to represent systems and their interactions-such as inputs, processes, and outputs-and energy and matter flows within systems. (MS-PS3-2)

Materials:

Lab Station 1: Hot and Cold Water (convection in Water)

• 2 same-size bottles or flasks
• Warm water source with red coloring added
• Cold water source (no coloring added)
• Index card, playing card, or piece of flat plastic
• Large shallow tub or pan to catch spills
• Paper towels

Lab Station 2: Cold Water and a Balloon (convection in Gas)

• Empty glass bottle, plastic bottle, or flask
• Balloons (2 per group)
• Container with ice
• Container with hot water
• Timer

Lab Station 3: Butter Boat (conduction in Metal)

• Container of very hot water
• Butter, about 1 tablespoon at room temperature
• Piece of foil, approximately 4” x 8”

Lab Station 4: Heat on Water (radiation)

• Heat lamp or lamp with 150 watt bulb
• Small cup of water at room temperature
• Thermometer

Procedure:

In this task, students will be faced with Hilton’s question: Why does a refrigerator get warmer when you leave the door open? Students will move through a series of 4 lab stations to explore three different ways that thermal energy can transfer from one system to another. In the end, students should be able to apply their observations and inferences to answer Hilton’s refrigerator question.

1. Set up lab stations with the appropriate lab equipment and lab station student direction handouts.

2. Place students in their project groups. Designate student roles and review the norms.

3. Ask a student volunteer in each group to read the letter from Hilton to the Science Wizard.

4. As a class or table group, take a vote to see if students think Mom or Hilton is correct about why the refrigerator warms up when the door is open. Remind students that after completing the lab stations, they may want to change their vote.

5. Students will complete their investigation handout.

Student prior knowledge:

Students know from prior lesson activities the following academic vocabulary; particle, particle drawing, source (e.g., heat source, and flame source), thermal energy, temperature, kinetic energy, thermal energy transfer, transfer, conduction, convection, radiation. Students have prior knowledge from using PhET simulation the relationship between kinetic energy, temperature, and thermal energy. Students know from prior activities/lessons that motion energy is properly called kinetic energy. Particles of matter with more kinetic energy can be drawn with longer arrows attached to them and the slower particles with shorter arrows attached to them.

Explanation:

At the macroscopic level, energy can be seen or felt or heard as motion, light, sound, electrical fields, magnetic fields, and thermal energy. At the microscopic level, energy can be modeled either as particle motion or as particles stored in force fields (electric, magnetic, or gravitational). The goal of this lesson is to help students make connections between the concepts of energy, particle motion, temperature, and the transfer of the energy in motion from one place to another. Moving particles or motion energy will be identified as kinetic energy. Temperature will be identified as the average kinetic energy of particles of matter. Through investigations, students will determine that there is a relationship between the temperature of a system and the total energy in the system, depending on the amount of matter present. As the learning sequence continues, students will connect the concepts that all matter (above absolute zero) contains thermal energy, or random motion of particles, and that thermal energy transfer is the transfer of energy from an area of higher temperature (more particle movement) to an area of lower temperature (less particle movement).

In this task, students will be faced with Hilton’s question: Why does a refrigerator get warmer when you leave the door open? Students will move through a series of 4 lab stations to explore three different ways that thermal energy can transfer from one system to another. In the end, students should be able to apply their observations and inferences to answer Hilton’s refrigerator question.

Questions and Answers:

What/Where is the radiator on a car? And what is its purpose?

Possible answer: A car's radiator is located near the front of the engine compartment [hood] and is used along with a water pump to move coolant liquid through the engine block in order to cool the engine. As the engine heats up due to fuel combustion, heat is transferred through conduction to the coolant, which is circulated back to the radiator where it is cooled before being circulated back to the engine.

Describe ways people try to cause or prevent heating and cooling by conduction, convection and radiation in everyday life.

Possible answer:

• The electronic devices in a desktop computer generate heat. You can feel the heat of the monitor rising out of the vents on its top surface. Processor units usually have small fans to help dissipate their heat by forced convection. If you remove the top of the processor unit, you should be able to see the fan at the back of the unit.
• Insulation placed into the walls and roofs of buildings reduces heat loss by convection. Being thick, fluffy stuff, air cannot move easily through all its mixed up layers of fibers. Instead, the warm air in the house is trapped on one side of the insulation, and the cold air outside the house is kept on the other side. Insulation performs the same role when it traps the cool, air-conditioned air inside a house away from the hot exterior air on the other side.
• Car engines generate a great deal of heat. The radiator, located just behind the grill, uses convection, conduction and radiation to keep the engine cool. Water is circulated with a pump (forced convection) in pipes that run through the engine block, and heat from the engine is transferred by conduction to the water. The water is carried to the radiator, where it flows through much smaller pipes running past hundreds of small metal folds. Heat is transferred from the water to the metal folds, again by conduction. When the car is in motion, air moves over the surfaces of the radiator, and heat is carried away by convection. When the car is not moving, heat leaves mostly by radiation. All the folds of metal in the radiator create a great deal of surface area from which radiation can occur. Most cars also have a thermostatically controlled fan that operates when the car is not moving but the engine is so hot that radiation alone is not adequate for cooling.

What might be some examples of cooling and heating "mechanisms" that occur in nature? What do animals do if they need to cool off or warm up?

Possible answer:

• Many animals lie down on cool, damp surfaces to help them lose heat by conduction. Others burrow down to where the ground is even cooler. Still others seek out cool water, another good heat conductor, to wade or swim in.
• Mammals that live in cold climates have thick, insulating fur. Many mammals that live where in regions with distinct seasons grow thicker fur during the winter and shed the excess insulating material during the summer when it is no longer needed.
• When their hives get too warm, bees use their wings to fan the hive interior, which is another example of cooling by forced convection.
• Cumulus clouds form when warm air at the Earth's surface rises very high into the atmosphere through convection.

Applications to Everyday Life:

The world we live in is full of energy. Energy is one of the most fundamental parts of our universe. Plants and animals need energy to grow and reproduce. Cars need energy to move. Refrigerators need energy to keep things cool. We need energy to cook our food. Everything around us and everything we do is connected to energy in one form or another.

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