Reaction Lab teaching notes
For middle school science teachers, chemistry teachers, co-op leaders and parents. Water and methane in one period, the unbalanced run, the lid and the lab bench, what students get wrong and where the app answers it, and the sheet and the setup.
Using this with a class? Make a free class and add your students yourself: each gets a username and password, with no email or Google account needed. Or give them one join code. Using Google Classroom? Post the link there; with a free class, the link also puts each student in your class, so you see their work. mytekDev is also available from the Google Workspace Marketplace, so your school's Google admin can install it for everyone.A first lesson: One period: balance water and burning methane, run one unbalanced on purpose, then take the lid off and do the zip bag lab beside the real one. A second period for the puzzles and the lab sheet.
Set up a free class Share to Google Classroom- About these notes
- One period
- The lab bench, beside the real lab
- What students get wrong, and where the app answers it
- What the app simplifies, on purpose
- Middle school and high school
- The sheet, the puzzles and the setup
- Standards
About these notes
Reaction Lab is a sealed flask on a scale. The student puts molecules in, writes the equation for what should come out by choosing how many of each product, and presses React. Bonds let go, every atom moves into a new molecule, and the scale either holds or it does not. It holds when the equation is balanced, because the same atoms are still in the flask.
It is written for MS-PS1-5: develop and use a model to describe how the total number of atoms does not change in a chemical reaction and thus mass is conserved. That standard leaves symbolic balancing and atomic masses out of what is assessed, so the middle school level balances with whole molecules and reads the scale in plain mass units. The high school level adds typed coefficients and atomic mass units.
One period
- Water, unbalanced (5 minutes) Everyone opens Making water and presses React without changing anything. An oxygen atom fades out, a red ghost stays where it was, and the scale drops from 34 to 18. Ask: did that atom really disappear? What did the equation say would happen?
- Water, balanced (10 minutes) They fix it with the + buttons only: one more hydrogen molecule, one more water molecule. React again. The scale holds at 36. Ask why three molecules can become two without any change in mass.
- Follow an atom (5 minutes) Rewind, tap one oxygen atom, React. Its path stays drawn. Ask where it started and where it ended.
- Burning methane (10 minutes) Balance CH₄ + O₂ → CO₂ + H₂O on their own. The Atoms card shows ≠ on any row that does not match yet.
- Lid off (10 minutes) Take the lid off and run methane again. The carbon dioxide and the hot water vapor escape out of the open top and the scale drops by exactly their mass. Ask where that mass is now.
- Exit question (5 minutes) Steel wool gets heavier when it burns. Where does the extra mass come from? Open the lab bench for steel wool to check.
The lab bench, beside the real lab
Three reactions have a lab bench view: baking soda and vinegar in a zip bag, steel wool burning, and a candle. Each sits on a kitchen scale that reads grams, with a magnifier the student drags over it to see the particles inside. The grams follow the particles' own run, scaled to classroom amounts.
- Zip bag, sealed: the bag puffs up and the scale holds at 152.4 g. Open cup: the carbon dioxide bubbles away and the reading falls to 151.4 g.
- Steel wool: it glows from gray to black and gains 0.6 g as oxygen from the air joins the iron. Only the outside of a pad burns, so a real gain is small.
- Candle: it loses 0.6 g as its carbon and hydrogen leave as carbon dioxide and water vapor. In a real class that takes 5 to 10 minutes; the app speeds it up. Candle wax is a much bigger cousin of methane, so the magnifier shows methane.
What students get wrong, and where the app answers it
| What students say | Where the app answers it |
|---|---|
| You balance by changing the little number | The subscripts are locked; pressing one names the different substance it would make |
| The number of molecules should be the same | Water: three molecules in, two out, same mass, and the guide says so |
| Atoms are destroyed and new ones made | Follow an atom, and the paths drawn for every atom |
| Burning makes things lighter, it goes away | Lid off on methane and the candle: the gas leaves and is still drawn in the room |
| Burning iron loses mass, rust weighs less | Steel wool on the lab bench gains mass, with the oxygen shown joining the iron |
| Gas has no mass | Gases are drawn as molecules, and the scale drops by their exact mass when they leave |
| The light adds mass | The flame's glow is drawn and never weighed, and How it works says why |
| The total number of atoms is what stays the same | The Atoms card counts each kind; the Same total puzzle has 4 atoms a side and is not balanced |
What the app simplifies, on purpose
- Atoms move to their new partners in one step. Real reactions happen in many small steps through collisions; the app shows where the atoms end up, not the mechanism.
- Atoms of one kind are identical, so a followed atom's path is one way it could go.
- Salts are drawn as touching clusters so they can be counted. Salts dissolved in water really split into separate ions, and How it works says so.
- Ball sizes are shrunk so the bonds show, the way a model kit does.
- Light and heat are drawn and never weighed.
- Photosynthesis and respiration are their net equations; a cell does each in many steps.
Middle school and high school
| Middle school | High school | |
|---|---|---|
| Reactions | 17: water, charcoal, hydrogen chloride, magnesium, salt, ammonia, peroxide, methane, limestone, zinc in acid, baking soda and vinegar, rust, steel wool, photosynthesis, respiration, an antacid, acid on marble | All 17, and propane, ethanol, ethane, the airbag, potassium chlorate, aluminum in copper chloride, lead iodide, iron in copper sulfate, acid and base, gasoline |
| Balancing | + and − buttons, whole molecules | Typed numbers |
| The scale | Mass units (oxygen 16, hydrogen 1) | Atomic mass units to two places |
| Puzzles | Four | Five, with the odd oxygen |
The sheet, the puzzles and the setup
The Sheet in the app's header is the student's write-up: their equation and a picture of their flask, the atom table, the mass before and after, the reactions they have balanced, and questions that quote their own numbers. They hand it in and it saves with the project; Print makes a paper copy.
Puzzles has five short ones: Fix the claim (a classmate says the scale broke because the steel wool got heavier), The missing molecule, Which picture is right, Same total wrong atoms, and The odd oxygen at high school. Every wrong choice says why it is wrong.
Setup is for you: the level, which reactions are on the shelf or one for everyone, whether a reaction counts as done only after it has also been run unbalanced, the sheet's questions, up to ten of your own, and a printed answer key with the smallest whole numbers for every reaction. Press Done, save, and hand the project out as the starter.
Standards
- MS-PS1-5: atoms are conserved in a reaction, so mass is conserved (the whole app).
- MS-PS1-1: models of molecules and extended structures (the molecules and the salt clusters).
- MS-PS1-2: properties before and after a reaction (the lab bench).
- HS-PS1-7: mathematical representations of conservation (the high school level's atomic mass sums).
- Crosscutting concept, Energy and Matter: matter is conserved because atoms are conserved.
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Page last reviewed November 2026.
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