A nail turns to rust, a cake rises in the oven, a cold pack gets icy in seconds with no freezer. In each case, matter transformed into something brand new. How?
By the end of this lesson, you will be able to:
Click a card to see what each word means. Click it again to close it. You'll meet every one of these in the lesson below.
Look closely at three everyday events. In each one, the stuff you started with seems to vanish, and something completely different appears in its place.
All three mysteries have the same answer: the atoms didn't disappear - they were rearranged into new substances.
A chemical reaction is a process that transforms a set of chemical substances into one or more new substances. During a chemical reaction, bonds are broken and new bonds are formed between atoms.
Melting ice is NOT a chemical reaction, because no new substance forms. Solid water became liquid water - but it's still water, made of the same molecules. The shape and state changed; the substance did not. A real chemical reaction always produces something new, with new properties: wood becomes ash, shiny iron becomes crumbly rust.
🕵️ You be the judge. For each change below, ask the one question that matters: did a new substance form? Then click your answer.
A chemical equation is a recipe. Follow the color coding: teal is the reactants (what you start with), green is the products (what you end with), and the gold arrow means "reacts to form."
Reactants are the starting substances present before the chemical reaction occurs. Products are the final substances remaining after the chemical reaction occurs. Read every equation left to right: before → after.
Atoms never vanish during a reaction, and they never appear out of nowhere. Every atom that goes in must come out - just regrouped into something new.
The Conservation of Matter means matter cannot be created or destroyed, only rearranged. The same atoms that started in the reactants are still there in the products - they have just connected to different partners to form new substances.
Remember the campfire and the cold pack from the start of the lesson? One blasted heat outward; one pulled heat inward. Every chemical reaction does one or the other.
🌡️ Hold the thermometer. For each reaction below, decide: does the environment get hotter (exothermic) or colder (endothermic)?
You can't see atoms rearranging - but reactions leave clues. Watch for these four signs that a new substance may have formed.
The campfire, the cold pack, and the rusty bike. Now you can explain every one of them like a chemist.
Everything from this lesson in one place: the words to know and the goals you worked toward.
| Term | Student-Friendly Definition |
|---|---|
| Chemical reaction | A process that transforms substances into new substances. Bonds are broken and new bonds are formed. |
| Reactants | The starting substances present before the reaction occurs - the left side of the equation. |
| Products | The final substances remaining after the reaction occurs - the right side of the equation. |
| Conservation of Matter | Matter cannot be created or destroyed, only rearranged. The same atoms appear in the reactants and the products. |
| Atom Rearrangement | During a reaction, bonds between atoms break and new bonds form. The atoms regroup into new substances. |
| Exothermic | A reaction that releases energy (heat or light). The environment gets warmer. Exit = out. |
| Endothermic | A reaction that absorbs energy (heat or light). The environment gets cooler. Enter = in. |
| Learning Goals | How You Showed It |
|---|---|
| Decide whether a change is a chemical reaction (6.MS-PS1-5). | You sorted six everyday changes by asking the one question that matters: did a new substance form? |
| Read a chemical equation and identify reactants and products (6.MS-PS1-5). | You read the color-coded anatomy of 2H₂ + O₂ → 2H₂O and identified each side of the arrow. |
| Use a particle model to show that atoms rearrange and matter is conserved (6.MS-PS1-5). | In the Atom Rearrangement Lab you watched 2 H₂ + O₂ regroup into 2 H₂O - the same 4 hydrogen and 2 oxygen atoms before and after. |
| Classify reactions as exothermic or endothermic (6.MS-PS1-6). | You sorted six reactions by what happens to the temperature of the surroundings. |
Five questions covering everything you discovered, including an equation for you to check. Answer every question, then submit.
Chemical reactions connect to everything else in the matter unit. Extension challenges: hunt for three chemical reactions in your kitchen tonight and write the evidence for each (color change? gas? temperature change? new solid?). Or sketch a particle model that shows the atoms in baking soda + vinegar rearranging into new products - and label which atoms ended up where.