Monster Mouths

What are Monster Mouths?

Engineer a creature that can move its giant mouth with air pressure! Learners build a pneumatic system from pistons, cylinders, and a connecting tube, then design a unique monster face that opens and closes when air is pushed and pulled through the system. This Spark weaves science, engineering, and creature design into one hands-on challenge where every monster looks — and sounds — different.

Time Needed:
15-40 minutes. If used during an event, they can be set up in a 15-minute quick build activity station.
Grade Level:
Pre-K and up
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Monster Mouths Quick Start Guide

Monster Mouths Storytelling Handout

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Overview

Monster Mouths introduce learners to pneumatics — the science of moving things with air pressure. Each learner receives two pistons and cylinders, a plastic connector tube, a wooden stick, sticky foam strips, thin cardboard, and an instruction sheet. Using these materials they build a working air-powered system that transfers push-and-pull forces from one piston to another.

The build follows nine steps: learners explore their materials, assemble and test a pneumatic system, attach the cylinders to a stick, design and cut a monster face from cardboard, attach the face so the mouth moves, then test and iterate. Extensions invite learners to add creature features, create backstories with a printable story worksheet, or swap air for water to discover hydraulics.

Materials

Each learner recieves
  • Two pistons and cylinders
  • A plastic connector tube
  • A wooden stick (jumbo craft stick)
  • A sheet of sticky foam strips
  • One rectangle of thin cardboard
  • An instruction sheet in a reclosable bag
What you need to provide

Scissors for cutting the cardboard mouth and any additional creature features.

Markers or drawing tools for designing the monster face on the cardboard rectangle.

Optional resources
  • Extra cardboard scraps or construction paper for learners who want to redesign their face or add 3-D creature features
  • Standard tape for reinforcing attachments if sticky strips lose hold
  • Additional art materials (colored paper, stickers) for creature features like arms, teeth, hair, or hats
  • Printable Creature Feature design sheet for planning faces before drawing on cardboard
  • Printable story planning worksheet for the storytelling extension
  • Colored water and a container for the hydraulics extension

Key Challenges

  1. Build an air-powered system from pistons and cylinders. Learners assemble two pistons and cylinders connected by a tube, creating a pneumatic system that transfers force through air pressure.
  2. Design and attach a creature face. Learners draw, cut, and attach a cardboard face so the mouth separates into top and bottom halves that open and close with the piston movement.
  3. Apply the engineering design process. Test, troubleshoot, and iterate — adjusting sticky strips, repositioning parts, and solving problems like stuck systems and floppy faces.
  4. Make it unique. This is a STEAM challenge — every monster should look different from the example. Learners add creature features, create backstories, or explore hydraulics by filling a cylinder with water.

Learner Goals

MUST
  • Assemble two pistons and cylinders connected by a tube into a working pneumatic system.
  • Demonstrate that pushing one piston moves the other piston by transferring air through the tube.
  • Identify the key components — piston, cylinder, and tube — and explain how they work together.
  • Attach a cardboard face to the pneumatic system so the mouth opens and closes.
SHOULD
  • Explain that the system is pneumatic — meaning "moved by air" — and describe how air flows between the cylinders.
  • Troubleshoot common problems such as stuck systems (both pistons in or both out) and floppy face attachments.
  • Create a unique monster design that looks different from the instructional example.
COULD
  • Add 3-D creature features such as arms, teeth, hair, or hats using extra materials.
  • Create a character backstory using the story planning worksheet — naming their monster, giving it a home, and writing a first/next/last narrative.
  • Perform a puppet show by introducing their monster to a neighbor and acting out a story.
  • Explore hydraulics by replacing air with colored water in one cylinder and observing the difference.

Extension Activities

  • Creature Features: Make your Monster Mouth one of a kind! Add arms, teeth, hair, a silly hat, or other 3D features using additional cardboard, paper, adhesives, and art materials. Every creature should look different from the example — problem solving and creativity is what’s most important.
  • Story Time: Use the printable story planning worksheet to write your creature’s backstory. What’s its name? What does its voice sound like? Where does it live? Introduce your Monster Mouth to a neighbor and put on a puppet show — what happens first, next, and last?
  • Hydraulics Challenge: Get a little messy! Fill one cylinder with water (add food coloring to make it easy to see) instead of air. When you move things with fluids instead of air, it’s called a hydraulic system. How does it feel different from pneumatics?
  • Air Pressure Experiment: Challenge learners to push both pistons into the cylinders at the same time. Can they feel the resistance as the air is compressed? See who can push both all the way in — they’re experiencing how air is a real material that takes up space.

Step-by-Step Guide

Pre-Activity Questions
Pre-K - Kindergarten
  1. What happens when you blow air out of your mouth? Can you feel it on your hand?
  2. What do you think will make the monster’s mouth open and close?
1st - 3rd Grade
  1. What is making the monster’s mouth open and close?
  2. When you push air into a balloon, what happens? Where does the air go?
  3. Can you think of something that moves using air?
4th - 8th Grade
  1. What do you think the word “pneumatic” means, and where might pneumatic systems be used in real life?
  2. How do you think pushing air through a tube could create enough force to move something?
  3. If you replaced the air with a liquid, would the system still work? Why or why not?
Pro Tips
  • It’s theirs to keep. Remind learners from the start that this project belongs to them when they’re done — watch how their engagement increases when they know they get to take it home.
  • Ask before you fix. When a learner is struggling, ask questions before offering fixes. Point out what you see and ask what they think might be causing the challenge. Avoid getting hands on or fixing their project for them unless absolutely necessary.
  • Peer power. If you’re in a group, invite other learners to help support each other. Peer support builds confidence and creativity.
  • Keep your example simple. When making your demo monster face, keep the design simple so your learners can be more creative than you. A big set of eyes and a mouth is plenty.
  • Sketch first, cut once. Encourage learners to sketch their face design with pencil on the cardboard before committing with markers or scissors. Practice making faces on scrap paper before drawing on the cardboard.
  • Have backup materials ready. Keep extra cardboard scraps or heavy paper handy for learners who might need another try if a cut or drawing doesn’t go as planned.
  • Save those sticky strips. When attaching cylinders to the stick, save the extra sticky strips — you’ll need them later to attach the monster’s mouth to the pistons.
  • From pneumatics to hydraulics. Ready for an extension? Ask learners: “What if you filled the cylinder with water?” Filling one cylinder with water instead of air turns the pneumatic system into a hydraulic system — a great way to introduce a new engineering concept.

Step 1: Explore Your Materials

Question: What do you notice about the different pieces in your kit? How do you think they might work together?

  • Have learners open their reclosable bag and lay out all components: two pistons and cylinders, a plastic connector tube, a wooden stick, a sheet of sticky foam strips, one rectangle of thin cardboard, and an instruction sheet.
  • Ask learners to identify each piece before you name it — what do they think each part might do?
  • Point out that they will also need scissors and markers, which are not included in the kit.
  • Remind learners from the start that this project will belong to them when they are done — watch how their engagement increases!
  • Consider providing extra cardboard scraps or construction paper for learners who may want to redesign their face later.

Step 2: Assemble Pistons and Cylinders

Question: What do you think will happen when we connect these two cylinders together?

  • Start by pulling one piston out of its cylinder and leaving the other piston pushed in. This setup allows air to be stored in one cylinder at a time and to flow between the two when connected.
  • Push and twist the plastic tube onto the tip of each cylinder. It should feel snug — this keeps the air from escaping.
  • Introduce the vocabulary: a piston moves up and down to push air in a cylinder. A cylinder is where air is stored. The tube connects the two cylinders into a pneumatic system.
  • If learners struggle with the push-and-twist connection, encourage them to hold the cylinder steady and twist firmly — avoid doing it for them unless absolutely necessary.

Step 3: Test Your Pneumatic System

Question: When you push one piston in, what happens to the other one? What is making it move?

  • Have learners push and pull on one piston to see the other piston move in and out. If it is working, the motion should be smooth and visible.
  • Ask: "What is making the other piston move?" Guide learners to understand that pushing air through the tube is what moves the second piston — this is a pneumatic system, which means "moved by air."
  • Challenge learners to push both pistons into the cylinders at the same time and feel the resistance as the air is compressed. See who can push both all the way in!
  • If the system is stuck, check that one piston is pushed in and the other is pulled out. Both closed or both open means there is no air available to move between them.

Step 4: Attach Cylinders to the Stick

Question: How can you attach the cylinders so they stay firmly in place on the stick?

  • Use one sticky foam strip to tightly wrap and attach each cylinder to the wooden stick. Place each strip midway between the ends of the cylinder for the best hold.
  • Press the sticky strips down firmly — floppy connections will cause problems later. No one wants a floppy face!
  • Save the remaining sticky strips — you will need them to attach the monster's face in a later step.
  • Test the system with the stick attached: push and pull one piston to confirm the other still moves freely.

Step 5: Design Your Monster's Face

Question: What kind of creature will your monster be? What features will make it unique?

  • Use the Creature Feature design sheet to plan the face before drawing on the cardboard. Encourage learners to sketch with pencil first.
  • Draw the mouth line all the way across the cardboard so it divides the face into two separate pieces — a top and a bottom. This is critical for the mouth to open and close.
  • Add eyes and any other features, but keep your example simple so learners can be more creative than you!
  • Encourage learners to think about their design before committing with markers. If they make a mistake, they can flip the cardboard over and try again on the back.
  • Have extra cardboard scraps or heavy paper available for learners who need another try.

Step 6: Cut the Mouth

Question: What will happen when you cut along the mouth line? How many pieces will you have?

  • Cut carefully along the mouth line to create two separate pieces: the top jaw and the bottom jaw.
  • Once cut, hold the two pieces and move them apart and together manually to preview how the mouth will look when it opens and closes.
  • Remind learners to cut slowly and follow their line — this is a permanent change, so accuracy matters.
  • If a learner's cut goes off track, extra cardboard or construction paper can be used to create a new face.

Step 7: Attach the Face

Question: Which part of the face should stay still, and which part should move? Why?

  • Flip the face drawing-side down and close the mouth so it forms a solid shape again.
  • Lay the closed piston and cylinder on the back of the face. Use sticky strips to attach the cylinder to the bottom piece of the face — this is the part that will stay still.
  • Pull the piston out a tiny bit, then use sticky strips to firmly attach it to the back of the top piece of the face — this is the piece that will move up and down.
  • Press all sticky strips down firmly. If they keep coming off, have standard tape available as backup.
  • Ask learners to predict which piece will move before they test it — building intuition about the piston-cylinder relationship.

Step 8: Test Your Monster!

Question: Does your monster's mouth open and close the way you expected? What could you adjust?

  • Push and pull on the other piston — the monster's mouth should open and close!
  • If the mouth does not open enough or close all the way, try adjusting the top piece of the face up or down on the piston. Additional adhesive may help.
  • If the face is floppy or falling off, press the sticky strips down more firmly or add a piece of tape for reinforcement.
  • If the system will not move at all, check that one piston is pushed in and the other is pulled out — both open or both closed means no air can flow.
  • Ask learners questions before offering fixes: point out what you see and ask what they think might be causing the problem. Invite other learners to help — peer support builds confidence and creativity.

Step 9: Iterate!

Question: Now that your Monster Mouth is working, what could you add or change to make it truly one of a kind?

  • This is a STEAM challenge — every Monster Mouth should look different from the example. Challenge learners to make their creature unique with additional features, backstories, or engineering experiments.
  • Provide extra cardboard, paper, adhesives, and art materials for learners to add 3D creature features like arms, teeth, hair, or hats.
  • Encourage learners to introduce their Monster Mouth to a neighbor — what is its name? What does its voice sound like? Where does it live?
  • See Extension Activities for structured challenges including creature design, storytelling with printable worksheets, and a hydraulics experiment using water instead of air.
Post-Activity Questions
Pre-K - Kindergarten
  1. What happened when you pushed the piston in? What moved?
  2. Can you feel the air moving when you push and pull?
1st - 3rd Grade
  1. What pushes and pulls the air in your monster mouth?
  2. Where is the air stored in your pneumatic system?
  3. What does pneumatic mean?
4th - 8th Grade
  1. How does the pneumatic system in your Monster Mouth compare to pneumatic systems used in the real world, like bus doors or dental chairs?
  2. What happened when you tried to push both pistons in at the same time? What does that tell you about air as a material?
  3. If you redesigned the system with larger cylinders, how would that change the force and motion of the mouth?

Standards & Goals

Common Core ELA Standards

K-2
3-5
6-8

RI.K-2.7 – Use illustrations and words in a text to describe key ideas: Example: Learners refer to the labeled instruction sheet and visual diagrams in their Monster Mouths kit to identify which component is the piston, which is the cylinder, and how the tube connects them—using both pictures and text to understand the pneumatic system before assembling it.

SL.K-2.1 – Participate in collaborative conversations: Example: Learners describe to a partner what happens when they push one piston in and observe the other piston moving out, using vocabulary like “piston,” “cylinder,” and “air pressure” to explain how their Monster Mouth opens and closes during the testing phase.

RI.3-5.3 – Explain relationships between concepts in a text: Example: Learners explain the cause-and-effect relationship between pushing a piston and the mouth opening by tracing how air travels from one cylinder through the tube to the other, connecting the written instructions to the physical pneumatic system they built.

W.3-5.3 – Write narratives to develop real or imagined experiences: Example: Learners write their Monster Mouth character’s backstory using the story planning worksheet, developing an imagined creature with a name, home, and voice—then organizing a narrative with a beginning, middle, and end to perform as a puppet show during the storytelling extension.

RST.6-8.3 – Follow a multistep procedure when carrying out experiments: Example: Learners follow the nine-step Monster Mouths build sequence precisely, understanding that the order matters—pulling one piston out and leaving the other pushed in before connecting the tube, because reversing this sequence means the pneumatic system won’t transfer air correctly.

SL.6-8.1 – Engage in collaborative discussions with diverse partners: Example: Learners compare pneumatic and hydraulic systems during the extension activity, discussing what changes when water replaces air in the cylinder and debating why the Monster Mouth feels different to operate—building scientific argumentation skills through hands-on observation.

Common Core Math Standards

K-2
3-5
6-8

K.MD.A.1 – Describe measurable attributes of objects: Example: Learners compare the lengths of the piston when pushed in versus pulled out and observe how far the Monster Mouth opens, describing the relationship between how far they push one piston and how far the other extends—connecting physical measurement to the pneumatic system’s behavior.

K.G.A.1 – Describe objects using names of shapes and relative positions: Example: Learners identify the cylinder as a three-dimensional shape and describe spatial relationships during attachment—“the top of the face connects to the piston” and “the bottom of the face connects to the cylinder”—using positional language like above, below, and between.

3.MD.B.4 – Generate measurement data by measuring lengths: Example: Learners measure how far the piston extends from the cylinder at different push strengths and compare the distance the Monster Mouth opens, generating data about the relationship between force applied and mouth displacement in their pneumatic system.

4.OA.C.5 – Generate and analyze patterns: Example: Learners observe the push-pull pattern of their pneumatic system—when one piston goes in, the other comes out, and vice versa—identifying this as a consistent, repeating inverse relationship and predicting what will happen before each push or pull action.

6.RP.A.1 – Understand ratio concepts and use ratio reasoning: Example: Learners explore the 1:1 ratio of piston displacement in their Monster Mouths—observing that pushing one piston in by a certain distance causes the other to extend by roughly the same distance—and discuss how changing cylinder sizes would alter this ratio in a redesigned system.

6.EE.A.2 – Write, read, and evaluate expressions: Example: Learners express the piston displacement relationship as a variable expression — if pushing piston A in by distance d causes piston B to extend by distance d, they describe this 1:1 inverse relationship and predict what happens when the tube length or cylinder diameter changes.

Next Generation Science Standards (NGSS)

K-2
3-5
6-8

K-PS2-1 – Motion and Stability: Forces and Interactions: Example: Learners explore how pushing and pulling one piston causes the other piston to move in the opposite direction, observing firsthand that forces (pushes and pulls) can change the motion of objects—and feeling the resistance when they try to push both pistons in at the same time.

K-2-ETS1-2 – Engineering Design: Develop a simple sketch, drawing, or physical model: Example: Learners sketch their monster face design with pencil on the cardboard before committing with markers, planning where the mouth line will go so the face separates into two pieces that align with the piston-and-cylinder system—iterating on their design when the first attempt doesn’t work.

3-PS2-1 – Forces and Interactions: Cause and Effect: Example: Learners investigate how the force of pushing air through the tube causes the Monster Mouth to open, testing different push strengths to observe how harder pushes create wider mouth openings—establishing a cause-and-effect relationship between applied force and pneumatic system response.

3-5-ETS1-3 – Plan and carry out fair tests to identify failure points: Example: Learners systematically troubleshoot a stuck Monster Mouth system by checking whether both pistons are pushed in (no air to transfer), whether the tube connection is loose (air escaping), or whether the sticky strips are holding—isolating one variable at a time to identify the failure point.

MS-PS3-5 – Energy Transfer: Construct an explanation of energy transfer: Example: Learners explain how energy transfers through their Monster Mouths pneumatic system—the mechanical energy of pushing a piston converts to pneumatic energy as air compresses and travels through the tube, then converts back to mechanical energy to move the opposite piston and open the creature’s mouth.

MS-ETS1-2 – Engineering Design: Evaluate competing design solutions: Example: Learners compare their Monster Mouth’s performance when using air versus water (the hydraulics extension), evaluating which fluid produces smoother, more controlled mouth movement—and discussing trade-offs between the simplicity of air and the force consistency of water in their pneumatic-to-hydraulic redesign.

Troubleshooting & Pro Tips

Stuck System

When the system is stuck, it’s because there’s no air in either cylinder (both pistons pushed in) or air is trapped in both cylinders (both pistons pulled out). Make sure one piston is pushed in and the other is pulled out before connecting the tube, then test with a push and pull.

Mouth Won’t Open or Close Enough

If the face won’t open enough or close all the way, try adjusting the top piece of the face up or down on the piston. You may need to use more adhesive. Make sure the bottom of the face is stuck firmly to the bottom cylinder.

Floppy Face

Press the sticky strips down firmly on both the cylinder and the cardboard. If parts keep coming off, have some standard tape available for learners to reinforce the connection.

System Won’t Move

Check that the tube is pushed and twisted snugly onto each cylinder tip — if the seal isn’t tight, air escapes and the system loses power. Also verify that one piston is in and the other is out so air can flow between them.

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