# Heat Transfer: Conduction, Radiation, Convection

photo credit: Kmecfiunit

##### Key Ideas from Lessons:
• Heat is transferred through matter in three different ways: conduction, convection, and radiation.
• Conduction occurs when two objects of different temperatures are in direct contact with each other and heat is transferred from molecule to molecule.
• Radiation is the transfer of thermal energy that does not require contact or the presence of any matter between the heat source and the object being heated.
• Convection is the transfer of heat by the movement of currents in a fluid (a gas or a liquid). As a fluid is heated, it expands and becomes less dense. Due to its lower density, the heated fluid rises and cooler fluids take their place. This motion sets up a convection current that becomes the mechanism for heat transfer
• The motion (speed and direction) of an atom or molecule can change when it undergoes collision with another atom or molecule resulting in one speeding up and the other slowing down
##### Summary of Lessons:

Watch one or all of the tutorials and the Study Jams video posted in the resources below about the 3 types of heat transfer while students take notes. Go over their notes for accuracy. There are several ways to administer the tutorials: Whole class; individually with technological devices (chrome books, iPads, etc.); or flipped classroom where the tutorials and notes are homework and you review the notes with them in class.  Students usually have some trouble with convection and convection currents. I show a video of boiling water in slow motion (see resources) and ask students to describe what is happening. I model the process on the board.

Ask students how they could set up investigations to explore each type of heat transfer. You might want to have a table of possible materials to help brainstorm: a lamp, ice cubes, thermometers, metal board, wood board, food coloring, jar of sand, empty clear plastic containers…

In small groups students plan an investigation for each type of heat transfer and draw a model of what they think will happen. Once the design plan is approved by you, provide the students with the materials and let them have at it. The goal is to prove heat transfer occurred for each type of heat transfer: radiation, conduction, and convection. A bar graph with temperatures before and after would be useful in showing that heat transferred from the warmer object to the cooler one.  They will report their data to the class and the class will kindly evaluate their investigative process.

investigation showing convection

Convection current investigations: Most students will be able to demonstrate a convection example but it’s a bit harder to create a convection current demonstration in the classroom because a constant heat source is needed. If convection current investigations are lacking and you feel the students need more exposure to this process here are a few ideas: Show a video of a lava lamp and ask students to draw a model explaining the energy transfers and transformations that make it work. How can you create your own lava lamp? What materials would you need? Why?Show this video of convection currents that a teacher set up in his/her classroom. Ask students to explain how he/she set it up. This link also has a classroom friendly set up idea to show convection currents. It is also important that students understand that convection occurs in fluids–which includes gases. Not as easy to demonstrate in class, but these gifs are helpful in letting students “see” warm air rising.  Heat transfer by convection is a huge piece of many geological puzzles that students will be asked to explain throughout the year so it is very important they deepen their conceptual understanding of this energy transfer by the end of these lessons.

Another activity that connects heat transfer to students everyday life requires students to bring a photograph from home (that can be marked on) showing heat transfer. It is acceptable to bring a magazine or newspaper picture as long as the picture depicts a scene that is part of the student’s daily life.  Students will observe each scene and consider how heat is transferring in that picture  Have the following prompts available for each student:

• What makes you think that heat (thermal energy) is moving? Is there any evidence that you see showing heat transfer? (Remember: Why does heat even transfer in the first place?)
• Where does the heat come from and where does it go?  (It may be helpful for students to remember which substances are at a higher temperature and which are at lower temperatures.)
• How is the heat transferring: conduction, radiation, convection? How do you know?

Pass out construction paper. Students glue or tape their picture to the top half. They circle and label at least one example of each type of heat transfer. Underneath the photo they explain their choices.

As a final assessment of all the energy lessons (What is Energy; Thermal Energy/Heat/Phase Change; and this one) students will complete a group quiz. These questions are from this website: http://assessment.aaas.org/pages/about. I find the questions and this website to be excellent formative assessments to gauge whether my students truly understand the specific content the lessons were designed to teach. Here is a quote from the website explaining the types of questions on the test:

The items and other resources available on this site were developed by AAAS Project 2061 with funding from the National Science Foundation. The items are different from most multiple choice science test items in that they:

• assess students’ conceptual understanding, not just facts and definitions,
• test for common misconceptions and alternative ideas students have along with their correct ideas
• are precisely aligned to the science ideas they are intended to test”

Students answer the questions on loose leaf paper but will only get credit for the correct response if they include evidence that supports their response. For example, “Choice A is correct because…….” If they can’t find evidence to support their choice, then their choice is probably wrong. They can use any resource available to them in class that we use to learn the content. All students must write out the answers, but only one student per group’s paper will be graded. This one student is randomly selected by my Class Dojo student selector so it is truly random. This encourages all students in the group to work together and make sure everyone is understanding because no one knows which students’ work will be collected. This activity promotes engaging in argument from evidence.

Resources:

Extension: