Teaching with Phone Lab

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Phone Lab is one phone in 3D and a card beside it. The student chooses the size, the materials, the screen and the cameras, and the card says what those choices add up to: how long the battery lasts, what the phone weighs, whether the cameras fit inside, how it sits in a hand, and what it costs. Every number comes from the phone as designed, so two students with the same phone see the same card.

Students arrive wanting to make a phone that looks good, and the first five minutes give them that: a shape, a color, cameras and a name on the back. The teaching starts when the app asks them to make it thinner. If time is short, do that part and Open it up, and skip the rest.

The app opens on a plain gray phone. There are no brands, no logos and no real models in it, and nothing to buy.

Two periods

Period 1: a phone is a stack, and thin has a price.

1. Make it yours (10 minutes) Students drag the phone to look around it, then pick a shape, a color and a number of cameras. A short guide at the top of the panel walks them through. Typing a name under Name on the back puts it on the phone and turns the phone around to show it.
2. Make it thinner (5 minutes) The guide asks for it: open Size and thickness and pull Thickness down. On the plain starting phone, going from 8.0 to 6.0 millimeters takes the battery from 4,500 to 2,850 mAh and the card from about a day to runs out by dinner. The one camera, which stuck out 2.0 millimeters, now sticks out 4.0. For a short while the card shows the old value under each line that moved, in orange.
3. Ask before opening it (5 minutes) Ask the class why the battery got smaller when nobody touched the battery. Take guesses. Most will say a thin phone has less room, which is right, and nobody will say what took the room.
4. Open it up (10 minutes) Open it up slides the phone apart into seven layers, front to back: cover glass, screen, battery, board, cameras, frame, back. With it open, students drag Thickness and watch. The glass, the screen and the back stay as thick as they were. The battery is the layer that grows and shrinks. That is the answer to the question.
5. Make the cameras fit (5 minutes) Still open, students push Thickness up until the card says the cameras fit inside. For the main camera that is 10 millimeters. Ask what they would give up to get there: at 10.0 millimeters the starting phone weighs 192 grams, up from 166, and the battery holds 6,150 mAh.
6. Other trades (10 minutes) Let them find more. A steel frame takes the starting phone from 166 to 194 grams. A metal back stops wireless charging. An LCD screen is cheaper and thicker, so the battery behind it is smaller. Have each student say one trade out loud in the form: I made it this, and it cost me that.

Period 2: design for someone, test it, and argue from the numbers.

1. Pick a customer (5 minutes) Under Customers there are six. Each has musts, which cannot be broken, and wants, which are scored out of 100. The plain starting phone breaks a must for five of the six. Or choose one customer for the whole class in Setup.
2. Musts before wants (10 minutes) Students change the phone until every must is met. While one is broken the card says so and shows no score, so nobody can chase points on a phone that fails. This is the difference between a constraint and a criterion, and it is worth saying in those words once they have felt it.
3. Test it (10 minutes) Under Tests, students put the phone on the bench: Drop, Pocket, Dunk, Charger, A day, Hand and Fix it. Each plays out on the phone and says what happened. Changing the phone clears the results, because it is a different phone. Ask why that is fair.
4. Keep two, compare (10 minutes) Keep this design saves the phone as it is, up to three. Students keep one, change something on purpose, keep the second, and press Compare to see them side by side with the customer's score for each.
5. The sheet (10 minutes) Sheet in the top bar: the phone's picture and numbers, the tests run, the customer, the designs side by side, and the written questions. Hand in needs an answer to every question.

What students get wrong, and where the app answers it

These are things to listen for. We found no study of what students this age believe about how phones are built, so the left column is not measured.

The six customers

The score reads the design, not the tests a student happened to run, so it is there the moment a customer is picked and it moves with every change. The kid's brief is always scored with the smaller hand.

The grandparent's brief says a battery that goes well past a day. The model's longest answer in practice is more than a day; two days cannot be reached, and the brief does not ask for it.

The seven tests

The same phone gets the same result every time. A real drop is partly luck, and the app says so in How it works. Leaving luck out lets a class argue from one result.

The plain starting phone survives two of three drops (its glass back cracks), lets water in at the sink, charges on the pad, and scores 4 out of 10 for repair.

What the app simplifies, on purpose

• A phone here is a simple stack. Real phones fit their parts together more cleverly, and real thin phones hold more battery than ours do, by making the battery wider. Our batteries come within about a quarter of real phones of the same size, and run small for thin ones.
• From published figures and standard reference values: how much a battery holds for its size, how heavy each material is, and what one real phone's screen and cameras cost.
• Our own estimates, set so a normal phone comes out normal: how deep each camera is, how thick each layer is, how many hours a charge lasts, the drop scores, the hand sizes and most of the costs.
• The cameras stick out a little less than on real phones with big cameras, where the bump is often 2 to 4 millimeters.
• The hours are mixed use on a waking day, with the screen on some of the time. A 120 Hz screen costs 9 percent of the hours here, which is the low end of what tests of real phones have found.
• The thumb's reach is a full stretch, not a comfortable one. We found no table of hand sizes for ages 10 to 14, so the three hands are judgments.
• Tougher glass scratching a little more easily is a tendency in real glass, not a rule. Sand in the Pocket test means quartz, the hard grain in most sand.
• The brain, the memory and the radios are one fixed cost, because the student does not choose them. On a real phone they cost the most.
• The shop price is the parts times about two and a half, which is what one real phone's numbers came to. Other phones differ.
• Fast charging and the headphone jack change the cost and how the phone looks. Nothing else in the model reads them.
• Left out altogether: choosing the chip and memory, the radios and antennas, software, heat, speakers, and selling the phone.

An independent review read every number in the model, the help text and the answer key against sources before the app went live. What it found wrong was fixed, and what is still a judgment is in the list above.

Middle school and high school

The level is a menu in the top bar. The phone, the card, the customers and the tests are the same on both. High school adds one question to the sheet, about why a 5,000 mAh phone does not always outlast a 4,000 mAh one, and prints the hours of mixed use beside the battery on the sheet.

Grade 5 works at the middle school level. The reading is short and the words are plain: thickness, layers, grams, millimeters.

The sheet, Setup and the answer key

The sheet has the phone's picture, its body, screen, cameras, battery, weight, fit in the hand, toughness and cost, the tests run on it, the customer, the kept designs side by side, and the written questions. The usual six ask who the phone is for, what the criteria and the constraints are, which of two kept designs is better and what number shows it, what a failed test led them to change and what that cost, one trade made on purpose, and why a thinner phone runs out sooner. Hand in needs every answer, and editing an answer after handing in takes the sheet back. Print gives the sheet alone.

Setup, in the top bar, is for the teacher. It sets the level, lets everyone pick a customer or gives the whole class one, picks which questions are on the sheet, adds up to ten of your own, and prints the answer key. The key lists what a good answer to each question has in it and the standard each question fits.

The choices are saved in the project. Set it up, save, and share the project with the class as a starter. Start over gives a student a fresh phone and keeps your Setup.

Standards

• NGSS MS-ETS1-1: define the criteria and constraints of a design problem with sufficient precision to ensure a successful solution, taking into account relevant scientific principles and potential impacts on people and the natural environment that may limit possible solutions. The customers' musts and wants.
• NGSS MS-ETS1-2: evaluate competing design solutions using a systematic process to determine how well they meet the criteria and constraints of the problem. Keep, Compare and the customer's score.
• NGSS MS-ETS1-3: analyze data from tests to determine similarities and differences among several design solutions to identify the best characteristics of each that can be combined into a new solution to better meet the criteria for success. Two or three kept designs, compared and combined into the next one.
• NGSS MS-ETS1-4: develop a model to generate data for iterative testing and modification of a proposed object, tool, or process such that an optimal design can be achieved. Students use a model here; they do not develop one. The tests and the card are the data, and each change is a round.
• For grade 5, NGSS 3-5-ETS1-1: define a simple design problem reflecting a need or a want that includes specified criteria for success and constraints on materials, time, or cost. And 3-5-ETS1-2: generate and compare multiple possible solutions to a problem based on how well each is likely to meet the criteria and constraints of the problem.
• CSTA 2017, grades 6 to 8. 2-CS-01: recommend improvements to the design of computing devices, based on an analysis of how users interact with the devices. The Hand test and the kid's brief.

Not claimed: NGSS physical science standards on energy or materials. The app's numbers for batteries and materials are good enough to design with and are not a lesson in either. The impacts on the natural environment named in MS-ETS1-1 are not modeled, apart from how easy the phone is to repair.

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