The Water Knife

About this resource

Some factories cut cake, foam, and even steel with a thin stream of water. Water is soft. How can it cut? The faster something moves, the more energy it has. In this one-week, 5-level Speed & Energy unit for 4th grade science (NGSS 4-PS3-1), students investigate a real mystery, then use their evidence to crack the case.

The Water Knife is part of Science Unlocked, a series of mystery-driven lesson sets. Every set opens with a real, surprising phenomenon, builds the science one level at a time, and ends with students solving the mystery in a claim-evidence-reasoning (CER) write-up.

Topics: claim evidence reasoning (CER), science phenomenon, review games.

What's included

• Teacher Deck (79 slides, PowerPoint). Answers are highlighted on the slides. Speaker notes tell you what to say and do, what to watch for, and how to support students or push GT students further. Prep slides and answer keys are hidden, so they skip during a slideshow.
• Interactive Student Deck (49 slides, PowerPoint + PDF). Students type in boxes, drag cards and check marks, and rate their confidence. Assign one copy per student in Google Classroom or your LMS.
• Google Slides versions of both decks. Click a button in the Google Slides Links PDF to make your own copy in Google Drive.
• Teacher Guide (20-page PDF). The standard, a week at a glance, a materials list, misconceptions to watch for, a run-of-show for every level, answer keys and sources.
• Student Printable (13-page PDF + a low-ink greyscale copy). The same tasks on paper in 12 pt type, for students without devices, sub days, or anyone who learns better with a pencil. Slide numbers match the Student Deck.
• Self-grading digital activity. SCORM 2004 and SCORM 1.2 packages for an LMS that accepts SCORM uploads, a web package, and a single HTML file that opens in any browser. Notes, sorts, matches, tables and multiple-choice items grade themselves, and students get a copy-and-paste backup of their work. A 2-page teacher quick start is included.
• Two whole-class review games that open in any browser: a Jeopardy-style game (6 categories, 30 clues) and Trashketball, where teams answer on whiteboards and then shoot for points.
• Kahoot! and Blooket import files. 48 review questions, one file per level plus an all-levels file, with a printable answer key.
• Start Here guide, HTML & SCORM how-to guide and Terms of Use, so you know which file to open first.

The 5 levels (about one 45–50 minute class each)

1. Motion Means Energy. Moving things have energy, energy can move between objects. Key activities: The Water Knife mystery, Moving-or-Still sort.
2. Faster Means More. Same object, more speed leads to more energy (patterns from observations). Key activities: Same Thing, Different Speed cards, Squirt Test demo, water ranking.
3. Dent Detectives. Investigation: faster ball leads to bigger dent (change of shape). Key activities: Ball-drop clay lab, Lab Conclusion CER.
4. Swing and Strike. Energy moves from a fast ball to a box (energy transfer). Key activities: Label the setup, pendulum lab, Case Clue: inside the water cutter.
5. Crack the Case. Stretch MS-PS3-1: mass AND speed, final explanation. Key activities: Hailstorm Stretch, Crack the Case CER.

Built for real classrooms

• Every level follows the same routine: "I can" targets with a confidence check, a warm-up, copy-it notes with a word bank, hands-on practice, a checkpoint students must pass to unlock the next step, and an exit ticket. A 10-item Mini Quiz wraps up the week.
• Level 1 opens with a Power-Up on the earlier-grade ideas this standard builds on (K-PS2-1, 3-PS2-2).
• The last level includes a middle school Stretch (MS-PS3-1) that every student tries and advanced students can take further.
• Hands-on lab (Dent Detectives: The Investigation). Student materials list: Tray of smooth, flat modeling clay; 1 golf ball (or other small, hard ball); Meter stick, cm ruler; Goggles for everyone. Safety notes are on the slides and in the Teacher Guide.
• Support is built in: word banks, sentence starters and support notes on the slides, plus GT extensions.

Standards

• NGSS 4-PS3-1: Use evidence to construct an explanation relating the speed of an object to the energy of that object. (Kentucky 4-PS3-1 uses the same wording.)
• SEP: Constructing Explanations and Designing Solutions · DCI: PS3.A · CCC: Energy and Matter
• Stretch: MS-PS3-1
• CCSS connections: 4.MD.A.1, 4.MD.B.4, RI.4.1, RI.4.3, W.4.2, W.4.9

Try the digital activity first

• Not sure the self-grading activity will work in your LMS? Download the FREE HTML & SCORM Sample and test it with your students before you buy.

Save with a bundle

• Grade 4 Energy (5 sets)
• Grade 4 Complete (17 sets)
• Science Unlocked Mega Bundle (all 89 sets)

Teach next

• The Rattling Window (4-PS3-2)
• The Super Bounce (4-PS3-3)
• Light From a Bag of Rocks (4-PS3-4)
• The Coal Museum’s Solar Roof (4-ESS3-1)

More from Mystery Lab Learning

• See every Science Unlocked set, and follow to hear when new ones are added, at Mystery Lab Learning.

Good to know

• The illustrations in this resource were created with AI image tools, and AI tools helped draft the lesson text. Every slide, answer key and lab step was then fact-checked against the sources listed in the Teacher Guide and proofread.
• Kahoot!, Blooket, Jeopardy!, Google Slides and PowerPoint are trademarks of their owners. This resource is not affiliated with or endorsed by them.
• License: one teacher, for use with their own students. Please buy an additional license for each colleague who uses it.