In a chemical reaction the reactants are used up and new substances, the products, are made. A word equation names them: reactants → products. It must include every product (burning a fuel makes water as well as carbon dioxide), but it shows no amounts or atoms.
A gas stove burns methane with a blue flame. Hold a cold spoon above it and drops of water appear. Where did the water come from?
You know the signs of a chemical change: a new substance is made. This lesson names what goes in and what comes out.
Engage: Commit to a prediction before you test anything. A wrong guess is fine: it shows you what to look for.
Explore: Try it on the board and compare what happens with your prediction.
Explain: Use the particle model to explain what you saw.
Practise: A few on your own, to check you have it.
Elaborate: Use the same idea in a new context.
Evaluate: Look back at your first ideas and what changed.
WidthMore contexts, same idea.
Make your prediction first. Help opens once you've locked it in.
EngageCommit to a prediction before you test anything. A wrong guess is fine: it shows you what to look for.
Engage: burning methane
ExploreTry it on the board and compare what happens with your prediction.
Explore: watch the reaction
Watch the counts beside the board. Which substances go down? Which new ones appear?
Try it yourselfNothing is saved: start again as often as you like.
Burn the methane until the target is reached.
Use the board. This ticks when you get there.
ExplainUse the particle model to explain what you saw.
Explain: reactants and products
In your book: write the word equation for burning methane, label the reactants and products, and add one sentence on what the equation does not show.
oxygenOxygen from the air takes part, even though you can't see it.
carbon dioxide
waterThe hydrogen in methane ends up in water.
Is it a sign that a chemical reaction has made a new product?
Bubbles of a new gas
A colour change in a mixture
A solid forming when two clear solutions mix
Ice melting into waterStill water: a change of state, not a new substance.
Sugar disappearing in teaDissolving: the sugar is still there.
PractiseA few on your own, to check you have it.
Word equations
Elaborate TypicalUse the same idea in a new context.
Elaborate: magnesium burning
Try it yourselfNothing is saved: start again as often as you like.
Burn the magnesium until the target is reached.
Use the board. This ticks when you get there.
Elaborate WiderUse the same idea in a new context.
Elaborate: why sodium hides
Try it yourselfNothing is saved: start again as often as you like.
React sodium with chlorine until the target is reached.
Use the board. This ticks when you get there.
EvaluateLook back at your first ideas and what changed.
Evaluate: look back
Write one sentence: "At first I thought… Now I think… because…"
Revision summary
In a chemical reaction the reactants are used up and new substances, the products, are made. Products have different properties.
A word equation names them: reactants → products. Read the arrow as "react to make".
Include every reactant and product: burning a fuel that contains hydrogen makes water as well as carbon dioxide; oxygen from the air is a reactant.
Heat and light are energy, not substances, so they are not in the equation.
A word equation shows no amounts and no atoms: formulas and balanced equations do.
For teachers
Students identify reactants and products, explain that products are new substances with different properties, and write word equations that include every product (AC9S9U07, nodes 1 and 3). About 28 minutes.
I can name the reactants and products of a reaction.
I can write a word equation that includes every product.
I can say what a word equation shows and does not show.
Before class
A concept tutorial for introducing or revising the idea; it does not replace doing the reactions (magnesium ribbon, zinc in copper sulfate, acid on marble chips). Set the width with ?width=minimum, typical (default) or wider. One lesson for two nodes: reactants and products (node 1) and word equations (node 3). It comes before Where do the atoms go? (node 2), so students name substances before they follow atoms.
Neither is a hinge node; node 3 asks for practice, so there is a Practise step. The prediction targets the usual error: leaving water out of a combustion equation (and forgetting oxygen as a reactant).
Board notes: the science board shows molecules as rigid particles. Magnesium oxide and sodium chloride are drawn as small particles too, although they are really giant lattices of ions; say so if asked. Heat given out shows as faster particles.
Running the lesson
Engage: tally the four options. 'Carbon dioxide only' and 'smoke and heat' are the ones to discuss.
Explore: ask which counts went down (reactants) and which appeared (products).
Explain: the reactant and product sort and the 'what it leaves out' question are the success criteria.
Practise: four reactions with the same check: every reactant, every product.
The hard part (on purpose)
Remembering every product. When a word equation is missing water, ask where each element in the reactants went, element by element.
When students get stuck
A student writes methane + oxygen → carbon dioxide. Ask: Methane has carbon and hydrogen atoms. Where did the hydrogen go? Fix: Into water. Every element in the reactants must end up somewhere in the products.
A student puts heat or light in the word equation. Ask: Is heat a substance you could collect in a jar? Fix: No: it is energy given out. Word equations list substances only.
A student leaves out oxygen when something burns. Ask: Would it burn in a sealed jar with no air? Fix: No: oxygen from the air is a reactant.
Stretch and support
Stretch: Write the word equation for respiration in your cells, and compare it with burning methane. (glucose + oxygen → carbon dioxide + water: the same products.)
Support: Give the frame: '… + … → … + …' with the reactants and products to place from a word bank.
Where it leads
Next: Where do the atoms go? (node 2) follows the atoms through the same burning methane; then balancing (node 4) adds the formulas and amounts that word equations leave out.
In class: magnesium ribbon burning (weigh the crucible before and after), zinc in copper sulfate, acid on marble chips with limewater. The progression's Wider also suggests First Nations processes that make toxic plants safe to eat; many of these combine physical steps (grinding, leaching in water) with chemical ones, so check the chemistry with local sources and community guidance before writing equations for them.
What each step is for
Engage: burning methane: The common error at this node is leaving out a product, usually water from burning; the distractors drop water, drop oxygen, or name things that are not substances.
Explore: watch the reaction: Watching the reactant counts fall and the product counts rise makes 'used up' and 'made' concrete before the words are named.
Explain: reactants and products: Naming reactants and products, tying products to new properties and the signs of a reaction, and saying what a word equation leaves out sets up symbolic equations.
word equations: Word equations need fluency (practise here): the same check each time, does it name every reactant and every product, across burning, neutralisation, displacement and acid with a carbonate.
Elaborate: magnesium burning: A second reaction on the board, with a metal and a single product, checks that students can name reactants and products from what they see.
Elaborate: why sodium hides: Reactive elements are found in nature as products of reactions, which explains why ores and salts, not pure metals, are what we mine.
Now you can
Name the reactants and products of a reaction.
Write a word equation that includes every product.