Lesson 3 of 12
Objective: SWBAT compare and contrast three specific ways that heat is transferred: conduction, convection, and radiation.
I start the lesson by playing How to Melt a Chocolate Bunny, which depicts a chocolate bunny being melted through the use of an iron, a heating lamp, and a hairdryer.
After watching, I provide about 3 minutes (1 minute per step) for students to Think, Pair, Share and brainstorm any other ways they can think of to melt the bunny. After students share in groups of 4, I ask for volunteers to share some of their ideas with the class. Every time a student shares, I list their ideas on the board or chart paper (to refer to later in the lesson).
I explain that while there may be many ways to melt a chocolate bunny, all of them have one thing in common. Heat must be present and transferred to the bunny in order to cause it to melt. I continue to share that any time we cook food, heat is required in order to prepare the food the way we want it. However, there is more than one way to transfer heat to the food we are cooking - in fact, there are three - which we will learn about today.
I pass out the Heat Transfer foldable and have students glue it into their notebooks. While it is drying, I have students access the Heat Transfer Animation on their technology devices. (This is a simple animation, so if you don't have student computer access it is easy to use by demonstrating.)
I explain that they explore the animation to investigate the three types of heat transfer. While they investigate, they take notes about each type of heat transfer on their foldable (underneath each diagram, and must include at least two examples, one from the animation and one of their own. They should also include a drawing or diagram on the outside of each flap that shows the meaning of conduction, convection, radiation.
As they are working, circulate and ask questions or request elaboration to develop the use of the scientific vocabulary.
I select 4-5 few students to display their work under the document camera, sharing their definitions, examples, and drawings. As they share, I assess understanding and encourage total active engagement by asking random students to verbally confirm their peers' ideas, or to provide refinements, using the following sentence stems:
- I agree with _________ because..., and I want to add...
- I disagree with __________ because..., and I believe...
(I have these stems written on the board for them to refer to throughout the activity.)
Next, the students participate in three mini labs. In each lab, they have the opportunity to make some popcorn, using a different type of heat transfer. The stations are as follows:
- Convection: Obtain a popcorn popper. Place the popcorn kernels in the popper. Plug in/turn on the popper. Hot air will transfer heat to the kernels, making them expand and pop.
- Radiation: Microwave a bag of microwave popcorn. You can also make your own microwave popcorn by tossing 1/2 cup of popcorn kernels with 1/2 teaspoon vegetable oil and salt, then dumping the popcorn into a brown paper lunch bag. Lock the corners of the bags by folding the corners down and tearing little tabs, then fold those tabs over. This prevents the bags from unraveling as the popcorn expands. Pop it in the microwave and run it for about 2 minutes. This is a healthier option than the greasy, buttery, chemical-filled topping that usually comes in the prepackaged bags.
- Conduction: Put oil in the bottom of a pan. Cover the bottom of the pan with popcorn kernels. Place the pan on the stove and turn on the burner to medium heat. Cover the pan with a lid - this is where clear glass lids are great. Periodically shake the pan so the kernels move around in the oil. Another option is to use Jiffy Pop, a prepackaged popcorn pan that can be placed directly on the stove top. These are safer and less messy, but do not allow students to see kernels pop.
Each station is equipped with Dixie cups labeled with their station number. Students get to fill a cup with a sample from each station so they can taste and compare the results of these different types of popcorn popping once they are finished.
Once students make and sample their popcorn, they complete the Popcorn Party Lab sheet to determine if they can identify the types of heat transfer that occurred with each cooking method. They also decide which type of heating method produced the best popcorn, based on taste and texture.
While this is a judgement call, I find it gives me a lot of insight into their understanding of the methods of heat transfer, and helps me to to determine whether they fully understand the differences between them.
Next, we revisit the list of ways we first listed to melt the chocolate bunny at the beginning of the lesson. As a ticket out the door, I provide each student with a blank index card and have them fold it into thirds, making three categories to sort the ideas according to the heat transfer involved in melting.