8th grade engineering activities

The mousetrap car rebuilt so 8th graders hit a target instead of a distance, five more design challenges, a free printable, and every 8th grade engineering Mission by standard.

  • By Skyler Carr, co-founder and CEO, Mission.io
  • Last updated

Who we are. Mission.io makes Missions: teacher-led, whole-class simulations where students use what they’re learning to work through a real scenario together.

Everything on this page works without us. Every 8th grade engineering Mission is at the end, by standard, free. (In Unstoppable Force, the crew picks drill bits by trial and error while an asteroid heads for a planet. Same loop as the car, bigger hallway.)

On this page

What 8th grade engineering looks like

Eighth grade engineering activities are design challenges where the class builds a model, tests it, and changes one variable at a time toward a target, with each student answerable for a piece. This page covers the four middle school engineering design standards, MS-ETS1-1 to MS-ETS1-4, with a challenge for each and a Mission where one exists. The 8th grade science activities page carries the investigations.

Middle school engineering is one 6 to 8 band of four expectations, and each state orders the band its own way. Define the criteria and constraints precisely (MS-ETS1-1). Evaluate competing solutions with a systematic process (MS-ETS1-2). Analyze test data to combine the best features of several solutions (MS-ETS1-3). Build a model that generates data for iterative testing (MS-ETS1-4). Eighth grade typically pairs them with physical science: forces, motion, and energy (MS-PS2, MS-PS3).

You know the activity that usually stands in for all of that. A mousetrap, a dowel, a couple of old CDs, and a hallway race where the farthest car wins. The hallway picks a winner, and nobody has to explain it. Move the goal from farthest to exactly five meters, and the lever, the wheels, and the mass all start to matter.

Six things that turn a build into engineering

The standards set the bar on purpose: NGSS raised engineering design “to the same level as scientific inquiry,” and at grades 6 to 8 that means defining the problem with greater precision, combining solutions, and testing and revising again and again (NGSS Appendix I). The catch is the period. A car that takes two of them to build had better be engineering.

  1. 1. A real problem with stakes the class can feel.

    “Farthest wins” is a contest. “The cart has to stop at the loading dock, and it has no brake” is a problem.

  2. 2. Apply, don't recall.

    A second round that only works with the spread from the first. If the car can be finished without testing anything, it isn’t engineering.

  3. 3. Group goals with individual accountability.

    The one most build challenges miss: one kid with the car, three kids with the stopwatch. When the group shared a goal and each student answered for a part, 84% of studies found a positive effect; without both, 17% (Slavin, 1991).

  4. 4. The teacher leads the thinking.

    The build video doesn’t ask questions. You do. Three at the car (what force moves it, what did the spread tell you, which change moves it toward the line) beat a worksheet of twenty at the desk.

  5. 5. A debrief where the class argues it out.

    The build is the setup. The argument afterward, about which variable moved the stopping point and where the spring’s energy went, is the practice the standards name.

  6. 6. A way to see who did what.

    If you can’t tell which student called the lever change and which one only wound the string, you can’t teach the design process. You can only measure the hallway.

The spring is fixed. Everything else is a decision.

The printable at the end of the next section puts all six on the table, with every card and log the activity uses, ready to copy. Get the sheet →

The mousetrap car, rebuilt for 8th grade (MS-PS2-2)

A wooden mousetrap’s spring arm, extended with a dowel, pulls a string wound on an axle and drives a car for distance. It’s on nearly every 8th grade list because it’s the physical science project with the longest history, and the way it usually runs is a car built at home, copied from a video, raced for distance, and never talked about again. Here’s the version that hits all six.

Time
Two periods; the chassis build is slow and the traps need supervision. The 45-minute cut: issue a pre-built chassis (CD wheels on a dowel axle, the trap mounted) so the lesson is the lever, the string, and the testing, and keep the debrief. Or run the build on day one and this lesson on day two.
Groups
Fours. With 30 students, seven groups of four and one of two, where the Mechanism Lead also measures.
Supplies for eight cars
8 wooden mousetraps ($2 each), 16 dowels, 32 old CDs or jar lids, string, cardboard or foam board bases, eye hooks, zip ties, and tape. About $30 the first year. Safety glasses on the Builder and the Data Lead at every release.
Standards
MS-PS2-2 (a change in an object’s motion depends on the sum of the forces on it and its mass) with MS-ETS1-4 (a model that generates test data for iteration). Energy transfer (MS-PS3-5) is the second honest content code.

  1. Teach first, 10 minutesApply

    Hold a loaded trap arm and release it with a short lever, then with a long one, and ask which pulls the string longer and which pulls it harder. Name the idea: the spring’s force is fixed, the lever trades force for distance, and the car’s mass and the friction at the axles are the forces working against it. Then name the three variables: lever length, wheel size, and car mass.

  2. The problemStakes

    A delivery robot company wants a spring-driven cart that travels exactly 5 meters on one trap, no farther and no shorter, because it has to stop at a loading dock without a brake. The criteria: three runs that each stop within 50 cm of the 5 m line. The constraints: one mousetrap, the chassis parts on the tray, 15 minutes per build round, and no outside parts.

  3. Four roles, one job eachAccountability

    On the sheet, and everyone signs their role’s box. Builder and Measurer swap between rounds.

    • Builder

      The only hands on the chassis, and the only one who sets and releases the trap, with the Safety Lead watching.

    • Mechanism Lead

      Decides the lever length and the string winding, and explains the force tradeoff before each change.

    • Measurer

      Marks each stopping point to the nearest 10 cm, three runs a round.

    • Data Lead and Safety Lead

      Records the runs, computes the spread, names the one variable to change next, and keeps fingers clear and the arm pointed away.

  4. You lead the thinkingTeacher leads

    Three questions, asked at the car: What force is moving the car, and what forces are stopping it? What did the spread of three runs tell you? What single change moves the stopping point toward 5 meters, and in which direction? The hardest part is not naming the lever. Let the spread name it.

  5. Two rounds, so the spread has to be usedApply

    Build and run three times, then 4 minutes to change one variable, then three more runs. One run proves nothing about a spring: the change is only worth making if the first three runs agree, and the Data Lead’s spread says whether they do.

  6. The debrief, 12 minutesDebrief

    Every team’s six stopping points on a class number line. Which variable moved the stopping point most, and did any team get it to move the wrong way? Why? Where did the spring’s energy go on a run that stopped short? Who on your team called the change that worked? The first question is the standard: the change in motion depends on the forces and the mass (MS-PS2-2).

  7. See who did whatSee who did what

    The observation sheet, four behaviors per student: explained a change in force words, measured accurately, disagreed with a reason, changed their mind when the data said to. You’ll catch about half the room in one period. The hallway test is where the waiting happens, and the waiting is when you tally.

(The car that goes farthest loses. It sailed right past the loading dock.)

The team that stops closest to the line owes the room one sentence in force words. Without it, that was luck.

The loading dock mousetrap car, free

Emailed now, ready to copy: the teacher page, four role cards, the safety rules with the criteria box and force diagram, the six-run log with the spread, and the four-behavior tally.

It’s on its way.

Check your inbox for the loading dock mousetrap car.

Email me the sheet. It comes as a PDF, ready to print. Unsubscribe anytime.

Five more 8th grade design challenges, by standard

Five more on every 8th grade list: what each one is, how it usually runs, and what it needs to be engineering, in the order the standards run.

Evaluate, combine, iterate, then forces

2. The robotic hand (MS-ETS1-2)

Needs cardboard, straws, string. Groups of four.

Students cut cardboard fingers, thread string tendons through straw guides, and pull the strings to make the fingers curl. It’s a good model of how tendons move a hand. As usually run in eighth grade, though, it’s a craft, and once the fingers curl, nobody asks what the hand can actually do.

The fix

  1. Give the hand a task: it has to pick up a cup.
  2. Keep a log of each string change the team tries, and mark the one that made the grip work.

See it fixed on the 8th grade STEM page →

3. The water bottle rocket (MS-ETS1-3)

Needs a 2-liter bottle, cardstock fins, a launcher and a bike pump, a field. Teams of four.

Teams add cardstock fins to a 2-liter bottle, fill it partway with water, pump it up, and launch it on the field. For most students it’s the last launch day they’ll get. As usually run, though, each rocket goes up once or twice, and nobody tracks what made one fly farther.

The fix

  1. Launch three times a round.
  2. Make one student the Data Lead, who logs every launch and works out the range of the three.
  3. Change one variable between rounds, like the amount of water or the fin shape.

See it fixed on the 8th grade STEM page →

4. The catapult with variables (MS-ETS1-4)

Needs a catapult with an adjustable angle, tension, and arm.

Students adjust a catapult’s launch angle, band tension, or arm length and see where the shot lands. The variables are built in, so the physics gets used. As usually run, though, students try a setting once and move on, and with no roles, no one can say who tested what.

The fix

  1. Run three trials at each setting, so one odd shot doesn’t throw off the result.
  2. Make one student the Data Lead, who logs every trial next to its setting.

No page for this one; three trials and a Data Lead are the fix.

5. The Rube Goldberg machine (MS-ETS1-4)

Needs whatever the chain reaction needs. Weeks long.

Teams build a chain reaction over several weeks, each step setting off the next. It already has a real problem and a design that has to work. As usually run, though, the student who designed it owns the whole thing, and the rest of the team can’t explain how it works.

The fix

  1. Give each student one step of the chain to own.
  2. Have each student explain their step in writing, what sets it off and what it sets off next, so every link has a name on it.

See it fixed on the 8th grade STEM page →

6. The simple electric motor (MS-PS2-3)

Needs a coil of wire, a magnet, a battery. Pairs.

Students wind a coil of wire, balance it over a magnet on a battery, and nudge it until it spins. The electricity and magnetism ideas get used, since the coil only turns when the forces line up. As usually run, though, it’s a fiddly solo build, and once it spins, nothing measures how well.

The fix

  1. Work in pairs, with a Winder who builds the coil and a Tester who runs it.
  2. Count the turns in 10 seconds, so each change to the coil shows up as a number.

No page for this one; the Winder, the Tester, and the turn count are the fix.

  • Our part · We make Missions

    Then the unit has somewhere to go

    Plenty of teachers rebuild these by hand every unit, and it works. A Mission is a teacher-led, whole-class simulation built from a unit you teach. The mousetrap car is MS-PS2-2 and MS-ETS1-4, and no engineering Mission carries either code. Unstoppable Force runs on the car’s trial and error, with drill bits. After the mousetrap car, run Unstoppable Force.

    You're at the helm, not on the hook.

    Spine-Backed Globster: the design cycle, as a Mission

    Spine-Backed Globster · Grades 6 to 12 · About 36 minutes · One device per student, plus your projector · Free with a teacher account

    In a computer lab, a student's arm shoots up in the foreground while a teacher at the projected screen gestures to the class and more hands go up behind her.
    Hands up across a computer lab, and a teacher at the screen.

    An invasive alien creature is wreaking havoc on a coral reef off the coast of Taipan. Before anyone proposes a fix, the crew has to analyze the data together and work out why the creature is causing so many problems; then the students write a proposal for a solution that eliminates the infestation. The story plays on the projector. The work happens at seven stations (Command, Engineering, Medical, Security, Science, I.T., Operations) and in the arguments between them.

    Every student is assigned to a team, and each team’s work is themed to it, from its own information and challenge to the same problem the rest of the crew is solving. The team gives a student a role in the story and people to lean on while you move between teams. You’re at the helm, asking which solution’s data holds up, and what they would take from the others.

    It’s built to the band’s first three engineering standards (MS-ETS1-1, MS-ETS1-2, MS-ETS1-3), with two ecosystem codes (MS-LS2-4, MS-LS2-5), and the vocabulary is the design unit’s: criteria, constraints, data, design solutions, biodiversity, invasive species. Run the mousetrap car first, and tell the class why: the reef needs a plan the data backs, and they’ve just learned that one good run proves nothing. The lesson prepares them. The Mission is what they’re preparing for.

    “What I love most is that it’s low-prep but high-impact.”

    Ginger Marsh, Middle school teacher, Cedar Middle School

    Will it work in my room?

    Students join with a class code: no student accounts, no student email, no passwords. Chromebooks, laptops, or tablets, plus your projector. Free for teachers, no credit card. Student data is covered by COPPA and FERPA, and we signed the Student Privacy Pledge. At about 36 minutes, Spine-Backed Globster fits inside a 45-minute period, with time left for the debrief.

    START FREE →

    Communication first, then two design Missions

    What the report shows

    A Mission.io class report: the class score in each of six skills, from knowledge and application to collaboration, critical thinking, and resilience, with the class chart across the year below.
    A class report from a real Mission: the class score in each of six skills, then each skill across the year.

    Every Mission produces a report for every student, built from what that student did across the whole Mission, on the skills the Mission captured. The six it can capture are Knowledge, Application, Initiative, Collaboration, Critical Thinking, and Resilience. The first two are what a test already sees. The other four are the human skills every school promises. The test shows what they know. The report shows the rest. SEE THE EVIDENCE →

    You taught it. Now find out who can use it.

    Who's behind it

    Mission.io is a research and design organization with one job: make collaborative, active learning something a teacher can run every unit instead of once a semester, and put a report in your hands when it’s over. Over a million students have run a Mission. The research behind them is funded by the National Science Foundation and the U.S. Department of Education’s Institute of Education Sciences, and Mission.io meets ESSA Level II standards, as validated by Instructure.

    8th grade engineering Missions by NGSS standard

    Spine-Backed Globster is one. There are 5 engineering Missions at 8th grade, numbered 7 to 11 below: three built to the middle school engineering standards, and two career Missions with no NGSS code. MS-ETS1-4 has no Mission, and three challenges on this page teach it, the mousetrap car among them. The car’s force standard and the motor’s are listed last, with no Mission here. Each code links to its standard on nextgenscience.org.

    Engineering design (MS-ETS1)

    Three Missions across the band’s first three standards, and Spine-Backed Globster carries all three. The fourth, MS-ETS1-4, is the car’s.

    Engineering design Missions for 8th grade, by NGSS code, with the standard that has none.
    NumberThe standardMissionMinutes
    7MS-ETS1-1, MS-ETS1-2, MS-ETS1-3, MS-LS2-4, MS-LS2-5 Define the problem, then evaluate and combine solutions for a reef losing its biodiversity to an invasive species (grades 6 to 12). On this page: 2. The robotic hand and 3. The water bottle rocket.Spine-Backed Globster36
    86.G.A.1, MS-ETS1-2 Use area and quadrilaterals to map infected tissue and remove it without harming healthy cells (grades 6 to 9). On this page: 2. The robotic hand.Infection34
    93-5-ETS1-1, 3-5-ETS1-2, MS-ETS1-2, MS-ETS1-3 Design an improvement to each of three islands’ defenses before a tsunami arrives (grades 5 to 8). On this page: 2. The robotic hand and 3. The water bottle rocket.Tsunami33
    MS-ETS1-4 Develop a model that generates data for iterative testing and modification, toward an optimal designOn this page: 1. The mousetrap car, 4. The catapult, and 5. The Rube Goldberg machine

    Engineering careers, from 4th grade up

    Two Missions from the career set that run at 8th grade and keep running through 12th. Neither lists an NGSS code; each one is a design problem with real constraints.

    Engineering career Missions that run at 8th grade, with no NGSS code listed.
    NumberThe standardMissionMinutes
    10Tunnel through an asteroid with different drill bits, tested by trial and error, before it hits a planet (grades 4 to 12; no NGSS code listed; made with US Synthetic)Unstoppable Force34
    11Pick a route, a landing point, and a first shelter on Mars (grades 4 to 12; no NGSS code listed; made with Hill Air Force Base)Mission to Mars45

    Forces, the car's and the motor's

    Two physical science standards this page’s challenges are built on. Neither has an engineering Mission; the 8th grade science page maps MS-PS2-2 to its forces Mission.

    The forces standards behind the mousetrap car and the motor, with the activity on this page for each.
    NumberThe standardMissionMinutes
    MS-PS2-2 A change in an object’s motion depends on the sum of the forces on it and its massOn this page: 1. The mousetrap car
    MS-PS2-3 Use data to find the factors that affect the strength of electric and magnetic forcesOn this page: 6. The electric motor
    START FREEMISSION BRIEF →

    Free teacher account, no card. Start with the Communication Mission, marked Start here in your library, then Spine-Backed Globster or Unstoppable Force, each after its 5-minute Teacher Preview.

    Also at this grade

    The 8th grade science activities page maps the grade’s science and engineering Missions by NGSS standard, Laser Labyrinth on the car’s MS-PS2-2 among them; the 8th grade STEM activities page rebuilds the water bottle rocket and fixes the robotic hand and the Rube Goldberg machine; and the 8th grade math activities page maps every 8th grade math standard.

Questions 8th grade engineering teachers ask

The 8th grade mousetrap car takes two periods. Is there a one-period version?

Yes: hand out a pre-built chassis, CD wheels on a dowel axle with the trap mounted, so the period goes to the lever, the string, and the testing, with the debrief intact. Of the five Missions, Tsunami is the shortest at 33 minutes, then Infection and Unstoppable Force at 34 and Spine-Backed Globster at 36, all done before the bell. Mission to Mars fills the whole 45-minute period, with no time left for the debrief.

Which 8th grade engineering standards does this page map?

The four middle school design standards. Missions cover MS-ETS1-1, MS-ETS1-2, and MS-ETS1-3. MS-ETS1-4 has none here; it belongs to the mousetrap car, the catapult, and the Rube Goldberg machine. The car’s force standard, MS-PS2-2, and the motor’s, MS-PS2-3, get rows of their own.

Is there an 8th grade Mission for the car's forces standard?

Not among the engineering Missions. The 8th grade science activities page maps MS-PS2-2 to Laser Labyrinth, a forces Mission. On this page, the nearest is Unstoppable Force: the same trial and error, on drill bits.

How do I keep thirty 8th graders and eight spring traps safe?

One set of hands per trap. Only the Builder sets and releases it, with the Safety Lead watching for fingers clear and the arm pointed away, and safety glasses go on the Builder and the Data Lead at every release. The pre-built chassis in the one-period version means every trap is mounted before class starts.

Do the 8th grade Missions line up with my state's standards, not just NGSS?

Spine-Backed Globster maps to 21 state science sets, Idaho, Oklahoma, and North Carolina among them. The two career Missions, Unstoppable Force and Mission to Mars, list no state sets.

Five meters on one mousetrap, and no brake

Day one, a challenge by hand with the sheet. Day two, Unstoppable Force after the mousetrap car, once you've watched its 5-minute Teacher Preview. Both free.

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