Designing a Melting Device Lab

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Objective

Students will be able to design, build, and test a device to best melt an ice cube.

Big Idea

The heat capacity of a substance can be used to engineer a melting device.

Introduction

In this lesson students work with various materials to design a device to best melt an ice cube.

  • This lesson aligns with the Next Generation Performance Expectation of  HS-PS 3-1 Create a computation model to calculate the change in the energy of one component in a system when the change in energy of the other component(s) and energy flows in and out of the system are known.  It does so because students utilize their knowledge of heat transfer to pick materials to use to melt an ice cube.
  • This lesson aligns with the Next Generation Crosscutting Concept 5: Energy and matter.  It does so because students are thinking about specific heat and how energy is transferred between systems.
  • This lesson aligns with the NGSS Science and Engineering Practice 6: Constructing Explanations and Designing Solutions: It does so because students are designing a device to best melt an ice cube.
  • This lesson also aligns with the NGSS Science and Engineering Practice 3: Planning and Carrying out Investigations: It does so because students are planning their own lab in terms of building a device and testing it out.

For this lesson various resources are needed including:

  • ice cubes
  • balances
  • timers- I use the ones on my computers (TimerTools) - or students can use their phones
  • various materials for building: I give each group a plastic container and then have lots of options available including pieces of wool, Styrofoam, copper, lead, aluminum, paper, cotton, and plastic.

Explain

5 minutes

I begin the lesson by giving students an overview of what we will be doing in the lab. 

  1. I first pass out the melting ice experiment lab paper and have students read it over to themselves for a few minutes.
  2. I then ask students what the goal of the experiment is and have them share out.
  3. Next I go over the paper with them...
    • I highlight the objective as "designing a melting device that will melt more ice than the other groups"
    • I go over all of the materials that I have at the front of the classroom. This melting device materials picture shows all of the materials that I provide to students.
    • I then talk to students about the procedure making sure to let them know that they are zeroing the balance before they weigh their ice cube.   I also tell them that they should not start their experiment until they have their device drawn and rationale written.
    • For the analysis I tell students that once they complete question #1 that they need to record their % on the class paper and then wait until the other groups are done before they start with the questions on the back of the paper.   I tell students that as they are waiting that they can organize their binders, work on other late work, or go back and play with one of the computer programs that we used during the unit.
    • This First Video shows me reviewing the lab with students in terms of the objective and procedure for building their device.

    • This Second Video shows me explaining to students how they will be analyzing their data and then recording on the class graph.

  4. Finally I have students work with their table groups and have them start the lab.

Elaborate

60 minutes

During this section of the lesson students are performing the lab.

  • Students are expected to work as a group but to also record data on their individual melting ice experiment papers.
  • As students are working I walk around between groups to make sure that everyone is on task and working together.  I make sure to ask students clarifying questions such as, "Why did you choose to use this material?"  "Why did you use this structure?"  "Where are you going to put the ice cube?"  "How did you calculate the % mass lost?"
    • These videos are examples of students explaining their devices:
      • Students explaining device movie #1: In this video the student demonstrates knowledge of metals helping the ice melt but does not use the term specific heat.  Additionally the student talks about cotton as acting as a blanket.
      • Students explaining device movie #2:  In this video the student talks about insulation and metals warming quickly but again does not refer to specific heat capacity.
      • Students explaining device movie #3:  In this video the student also talks about heat as conductors of metals and wool as a way to warm something up but again does not use the term specific heat that we discussed in the previous lesson.
  • I remind students that once they have found their % lost that they should work on something quietly while they are waiting for the other groups.  To help keep groups working efficiently, I make sure to push any group that is being slow to work a bit quicker.
  • Once all students have their % mass lost recorded on the class chart I have them flip to the back of their lab papers.  We then discuss as a class which device is the "winner" with losing the greatest percent mass. 
    • To do this I first have students look at the chart and decide which is the winner and we discuss how it is whichever loss the greatest percent of mass.  Here is an example of one class's chart .
    • I then walk over to whichever group won and pick up their device and have them explain what they did. This is a picture of one group's winning device.
    • I then go over the specific heats of the various substances with students showing how them how things like Styrofoam, paper, wool, cotton, plastic and wax have high values while lead, tin, copper, and aluminum have lower values.   This is a picture of the list I use to with students.
    • I help lead them to the idea that those with low heat capacities will allow energy to be transferred to the ice cube more easily; therefore, helping it to melt. 
  • Finally I have students finish the lab by answering the rest of the questions and then turning the lab into my basket.

Evaluate

After students turn in their labs I grade them using the rubric on the second page of the lab paper.

Here are some examples of students' graded labs.

In the first example Melting Device Student Example #1 the student shows that he understands how heat capacity plays a role in melting ice.

In the second example Melting Device Student Example #2 the student also shows that she understands how heat capacity plays a role in melting ice.  She also does a great job with drawing and describing her device.

In the third example Melting Device Student Example #3- the student mixed up heat capacity with the understanding that high heat capacity materials such as wood and wax would make things melt which is the opposite of what I was trying to teach.

In the fourth example Melting Device Student Example #4 the student also demonstrates mastery of what it takes to help the ice melt versus keep it frozen.