Heat Transfer demonstrations

Summary

Students will be given a chance to place their hands on two different objects and then predict on which an ice cube will melt more quickly.

Students will make a prediction as to what will happen when balloons filled with air and with water are held over a candle flame.

Determine the Type of heat transfer happening in a variety of demonstrations and identify instances of each type of heat transfer in their lives.

Learning Goals

Students learn that different materials may transfer heat at different rates.
Students learn that water absorbs heat rapidly.
Students learn that everyday appliances and machines make use of these characteristics.

Students classify the method of heat transfer in a variety of demonstrations.

skills: critical thinking, observation, questioning

key concepts: Heat transfers at different rates through different materials.
Water has a high capacity to absorb heat.

Heat can be transfered through conduction, convection, and radiation.

vocabulary: transfer, absorption, insulation

Context for Use

 middle school
setting: regular classroom or science lab
presentation: demonstration, with student tactile involvement
time allotment: 25 to 35 minutes
equipment: cast iron fry pan, wood cutting board, balloons, candle, ice cubes, lava lamp

Subject: Chemistry:General Chemistry:Thermodynamics, Thermodynamics:Heat
Resource Type: Activities:Classroom Activity
Grade Level: Middle (6-8)

Description and Teaching Materials

Prior to the demonstrations, students should have learned the three types of heat transfer: conduction, convection, and radiation.

Throughout the demonstrations, have students fill in the observation chart linked here: 

First, as a group, discuss and define what students remember about heat transfer and the three types of heat transfer.  Have them fill this in on their sheet for reference throughout the lesson.

1) The lesson can begin with giving the students a chance to place their hands on the fry pan and the cutting board at the same time. When all have had a chance to feel both items ask them to make a prediction - on which item will an ice cube melt more quickly. Set these two items aside with an ice cube on each. Discussion can be held with students to get their input as to what they observed and why they predicted what they did. Ask students to classify the type  of heat transfer (conduction) that is happening as the pan or the wooden cutting board transfers heat to the ice cubes.  This is a good time to discuss the conductive properties of metals vs. nonmetals. Ask students to discuss where the heat to melt the ice cubes is coming from. Return to fry pan and board. The ice cube on the fry pan will have melted more even though it felt cooler to the touch. Explanation: Heat moves more quickly through the fry pan melting the ice cube faster. Heat moves more slowly through board - the board has more insulating qualities.

2) Move to next demonstration involving heat absorption.
Show students two balloons - one filled with air and one with water. Ask them to predict what will happen if one is held to the candle flame. Hold both to the flame, one at a time. Air balloon will pop, water balloon will not pop. Students may be asked for their ideas why the water balloon did not pop. Explanation: Water absorbs heat so quickly that the heat from the candle is taken away from the surface of the balloon and it does not damage it. Discuss how students would like to classify the heat transfer- If you are holding the balloons near the flame but not in it, they will likely say radiationIf the balloon is touching the flame, they will likely decide on conduction.   You can show 

3) Lava Lamp- You will need to plug this in about 30 minutes before class so that it is fully working for your students to see the blobs of wax rising and falling in the lamp.  The lava lamp demonstrates convection currents because the light bulb (heat source) heats the wax that is near it.  The wax heats up, expands and becomes less dense, so it rises. The wax at the top of the lamp cools, becomes more dense and sinks.  Ask the students what will happen if you turn off the lamp/remove the heat source? What do they think will happen if you were in a 0 gravity environment?  This can lead to interesting discussions and involves critical thinking and predicting skills.

Move to a discussion of ways these concepts are put to use in our everyday life: car radiator, furnace radiator, home insulation, baseboard and in-floor radiant heat, convection ovens, earth's energy budget from solar radiation, rubber handles on pans, etc.

Teaching Notes and Tips

This activity involves the burning of a candle - you may need to have permission for this.
Your neighboring teachers may appreciate knowing that you will be burning candles and popping balloons as this can be loud.
Just in case, have something in which to catch the water if the balloon bursts.

Assessment

Students will draw the three demonstrations in their journals or on the student data sheet provided.  In addition, students will give examples of when they have experienced/seen conduction, convection, and radiation in their daily lives.

Download an editable google doc at the link below.

Heat Transfer Demonstrations Student Data Sheet

_____________________________________________________________________________________________________________________________

Heat Transfer Demonstrations

Define the following:

Heat Transfer: __________________________________________________________________________

Give examples of when you have experienced/seen conduction, convection, and radiation in action in daily life.

Conduction:

Convection:

Radiation: 

References and Resources

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How and Why did you Remix this Resource?

I like using demonstrations of heat transfer in class. The original activity focused on the fact that heat transfer was occurring.  I added information to this that expanded the lesson to focus on the different types of heat transfer.  I added a lava lamp demonstration in order to include an example of convection. I created a data sheet that students can fill out during the demonstrations to help them stay on task and to make connections between what they are seeing in the demonstrations and the three types of heat transfer.