Heat It Up


Jacob Ohnmeis

Unit Title:

Heat It Up





Estimated Duration:

9 Day of 75 minute class periods

Unit Activities:

Activity 1: CBL Discussion

Activity 2: Linear Sorting and Matching Activity

Activity 3: Solar Water Heater Challenge

Activity 4: Solar Water Heater Advertisement


July 2015

Unit Academic Standard

8.EE.B.5 – Graph proportional relationships, interpreting the unit rate as the slope of the graph.  Compare two different proportional relationships represented in different ways.

8.EE.B.6 – Use similar triangles to explain why the slope m is the same between any two distinct points on a non-vertical line in a coordinate plane; derive the equation y=mx for a line through the origin and the equationy=mx + b for a line intercepting the vertical axis at b.

8.F.B.4 – Construct a function to model a linear relationship between two quantities.  Determine the rate of change and initial value of the function from a description of a relationship or from two (x,y) values, including reading these from a table or from a graph.

The Big Idea (including global relevance)

While warm water is abundant to most of the students doing this project that is not the case for many around the world.  Designing a solar water heater in a limited space with cheap materials could be extremely helpful.  Hot water can be used to cook, clean, and if hot enough kill bacteria in non-cleaned water so it can be consumed.

The Essential Question

What can we create to heat water where electricity is not available?

The Hook

When students are asked about the sun, they describe it as hot and bright.  To understand how a solar water heater can be used, students must understand the power of the sun!  To do this, we are going to create a mini solar oven.  The hook takes about one class period (75 minutes), and I have them cook an egg in their oven.  You could also do a s’mores if you wanted!  This hook really gets them engaged, because they now see how powerful the sun is.  A link to the solar oven kit that I use is here and can also be found on ssww.com incase the link becomes inactive.: Mini Solar Oven.  All of the instructions for the mini solar oven come in the kit, so it is really worth the $12.99 it cost!

The Challenge

Description of Challenge (Either Product or Process is clearly explained below):

List the Constraints Applied

Build a solar water heater that can heat a minimum of .5 liters as quickly as possible.  The students will be given the same materials (listed under the constraints) and each material will be given a dollar value.  As they pick and choose the materials they will be using, they must calculate the cost it takes to make their solar water heater.  This helps them to understand the idea that just because their design looks cool or works well, doesn’t mean it is cost effective.  If a group brings in additional materials that were not provided, it must be approved by the teacher.  If approved, the teacher will assign a cost to that item so it can be added into their design.

**Update on Project Design

The students' initial design will be they are only allowed to change one variable to the water bottle that I provide to them for their solar water heater. Some students will spray paint the bottle, some will place it in some type of apparatus, another group might use foil to reflect sunlight, etc. Once the students have changed their one variable to their water bottle it will be tested. As a class we will analyze how each person's solar water heater did with that variable changed. 
The students will communicate the results for each of their designs, and then identify elements for their redesign. For the redesign, each group can use any of the data collected to create their final design. This design will then be tested to see what solar water heater works most efficiently.

The following materials

-5 Styrofoam cups

-1 16.9 oz water bottle

-a roll of aluminum foil

- 2 large black garbage bags

-a roll of tape


-a roll of reynolds Wrap

-a tin can


-an empty 2-liter bottle

-construction paper

-1 glue stick

Anticipated Guiding Questions
  • How can we heat water using solar energy?
  • What materials can be used?
  • Do certain materials conduct solar energy better than others?
  • Do certain colors conduct solar energy better than others?
  • How much water must we heat? 
  • How hot does the water need to get?  
Engineering Design Process (EDP)

Students will test and implement their solution when creating a solar water heater.  They will leave it outside for a total of 60 minutes, gathering results every 5 minutes.  The evidence that shows that the solar water heater works is that the temperature of the water increases more than the control of the experiment (the water bottle that is just sitting in the sun with no solar water heater). The students will calculate whose solar water heater had the highest temperature, the greatest rate of change over certain intervals, etc.  They then will create an advertisement to sell their solar water heater to engineers.  This is when I will invite different engineers into my classroom to check out their presentations and judge them.

The students will present their solution via a classroom presentation. The classroom presentation will be an advertisement on why someone should by and create their solar water heater.  As the students work on their unit, they are required to take videos/pictures of their progress as well as take notes on their developments.  Also, each material used in their project has a cost value, so they will need to calculate how much their solar water heater would cost.

The academic content that is being taught through this challenge is focusing on rate of change, slope, and understanding linear relationships between 2 different quantities. 


Common misconceptions for this unit are students thinking that “black is always the best.”  What I mean by this is that students understand quickly that the color black absorbs the most light, so they believe that everything in their design must be black.  Groups that do this will see their water temperature rise, but it will not be as effective as groups who also use the idea of reflecting the light.

Another misconception is that students believe that the hottest temperature “wins.”  While is very important that the students get the water temperature to a higher temperature, it is really based on their percent increase that would determine a winner in this challenge.  Also, they need to focus on making their design cost effective.  Each material used is designated with a cost.  Students forgot to consider this in their design, therefore making some of the designs very expensive.

Unit Activities

Day 1:  Pre-test and Hook

  1. Pre-test the students on prior knowledge (Lesson 1 Activity 0).
  2. Present students with the hook of creating a mini solar oven.  Materials and directions can be found here: Mini Solar Oven

Day 2:  Challenge Based Learning Discussion (Lesson 1 Activity 1)

  1. Once the students have completed the hook, their interest in the power of the sun should be heighted.  This is where we will complete Lesson 1 Activity 1, which is our Challenge Based Learning Discussion Activity.  To make the process go smoothly, I use the CBL template (Lesson 1, Activity 1, Worksheet A).
  2. As the Challenge Based Learning Discussion begins, use this Heat It Up Discussion PowerPoint to help guide the students. 
  3. NOTE:  This activity is extremely important.  This is where the students “develop” the challenge with your guidance, and this process helps the students engage in the content.

Day 3:  Linear Sorting and Matching Activity (Lesson 1 Activity 2)

  1. If timing worked well yesterday, present the students with the official Challenge of creating a solar water heater. Remind them to keep that idea in mind as you do this next activity.
  2. Put students in groups of 4, and these are the students who will be working together for the duration of this unit plan.
  3. Lesson 1 Activity 2 will be completed today.  The worksheet is titled linear sorting and matching (Lesson 1, Activity 2, Worksheet B).  It will be completed in groups, where students will work together to match graphs to different tables, equations, word problems, and given slopes/intercepts.  This provides students will multiple representations of how we can look at information. Activity 2 provides students with the knowledge of how we will look at our solar water heaters rate of change.
  4. At the end of class pass out the homework (Lesson 1, Activity 2, Worksheet C)

Day 4: Solar Water Heater Challenge, initial design (Lesson 2 Activity 1)

  1. Collect homework from the previous day and grade it.  Make note of students who struggled.
  2. Today the students will begin the challenge of creating a solar water heater.  Pass out the packet titled Solar Water Heater Challenge (Lesson 2, Activity 1, Worksheet D). 
  3. The students will follow the packet to help with their initial design before the final redesign process.
  4. Have each group pick one variable to test, and create their solar water heater to test that variable.  Make sure each group tests a different variable.  For example, have one group test the effect of painting the water bottle black while another group can test the effect of using aluminum foil to for reflection.

Day 5: Share Results of Variable Tests and Draw up design (Lesson 2 Activity 1)

  1. Students spent the entire class period gathering data on the variables they were testing, and they now must report out to the class of the results.
  2. Students will fill in these results in their Challenge packets (Lesson 2, Activity 1, Worksheet D). 
  3. Once all of the information is shared, each group of 4 will draw up their design for their solar water heater.  This is an important step in the EDP process.  If you do not require students to draw their design first before building, this project is not nearly as effective. 
  4. The drawing/blueprint of their design needs to be labeled with dimensions.

Day 6:  Build Solar Water Heater

  1. Once the students have completed their blueprint and it is signed off by the teacher, they may go ahead and start building their design. 
  2. Remind them to make notes on their blueprint in red pen if they change/alter their design.
  3. Lastly, make sure the students are creating instructions for how to replicate their model.  This is vital for the advertisement piece they will create in a few days.

Day 7:  Test and Collect Data from their Solar Water Heater

  1. Students will go outside to a designated area, and place their solar water heater. 
  2. They will take an initial temperature and record it in the challenge packet.  From there, the temperature will be taken every 5 minutes for the next 45 minutes.  Each time, the data will recorded.
  3. If time permits, let the students continue taking data till the remainder of the period.  The longer the solar water heaters can stay in the sun, the better!

Day 8:  Create advertisement for Solar Water Heater (Lesson 2, Activity 2)

  1. Now that the solar water heaters have been tested and data is gathered, they need to finalize the project by creating an advertisement for it.
  2. The students will have create an advertisement (a video, poster, pamphlet, etc.), get the idea approved by the teacher, and then present it to engineers the following day.
  3. Students can use the Solar Water Heater Rubric as a guideline (Lesson 2, Activity 2, Worksheet E).

Day 9:  Present advertisement to a panel of Engineers            

  1. A panel of engineers will be invited to the teacher’s classroom to observe the students advertisements.
  2. Give the engineers the Solar Water Heater Rubric so they can make notes during the presentations.
Additional Resources





Pre-Unit and Post-Unit Assessment Instrument

The Pre-Unit and Post-Unit assessment instrument is in the simple form of a pretest and a posttest.  The pre and posttest will be the same, to act as a reliable assessment instrument to show growth.