Matter and reactions for high-school physical science: study cards over three tiers, the tricky ones, a practice quiz at three levels — Foundation, On-Level, and Challenge — and a lab where you label a blank periodic table, sort twelve substances by bond type, put the steps of balancing an equation in order, and argue from two flasks whether mass was destroyed. Work here, or print it and use a pencil — both count.
An unbalanced equation. Count the atoms on each side: two hydrogens versus two, one oxygen versus two.
A subscript is part of the substance’s identity; a coefficient is just how many of them you have. Change coefficients only — changing a subscript to make the numbers work turns water into bleach and quietly answers a different question.
What people get wrong
⚠️People often think…
When a log burns and the ash weighs less, matter was destroyed.
Gases left the scale. Seal the same fire in a closed container and the mass does not budge. Rust is the same story in reverse — iron gains weight because it took oxygen FROM the air.
Mass that vanished is a gas that left.
⚠️People often think…
Two isotopes of an element have different numbers of protons.
Protons are what define the element — change those and you have a different element entirely. Isotopes differ in NEUTRONS; ions differ in ELECTRONS. Three particles, three different questions.
Salt conducts electricity, so a salt crystal on the table will conduct.
Conducting needs charges that can MOVE. In a solid crystal the ions are locked in a lattice and cannot go anywhere. Melt it or dissolve it and the ions come free — then it conducts.
Melted or dissolved, then the ions can move.
⚠️People often think…
Two elements in the same row of the table have similar chemistry.
It is the COLUMN that predicts behavior. Down a group, every element has the same number of valence electrons and behaves alike. Across a period you add one electron each step and the chemistry shifts every square.
Columns predict. Rows just count electrons.
Position, bond, property, conservation
1Watch one
Balance H₂ + O₂ → H₂O.
Count what you have: left, 2 H and 2 O. Right, 2 H and 1 O.
The oxygen is short on the right. Put a 2 in front of H₂O — never inside it.
Now the right has 4 H and 2 O, so the hydrogen is short on the left.
2H₂ + O₂ → 2H₂O. Four H and two O on both sides. ✓
2Do one with me
Fill in what the particles and the table tell you.
To balance an equation you change only the
Isotopes of an element differ in their
Similar chemistry is predicted by a shared
💬One sentence, then you move on
Why is changing a subscript not allowed?
3Try one
Rusted iron weighs MORE than the iron did. Where did the extra mass come from?
I want a hint first
Iron left in a sealed jar of pure nitrogen never rusts. What is missing from that jar?
💬Last one — then you're done here
Why does a salt crystal not conduct but salt water does?
Where this goes
Where this lives
Why a car rusts faster near salted winter roads, why baking soda and vinegar overflow a sealed bottle, why battery acid is measured in concentration and not in weight.
What this feeds
Next unit is forces, energy and waves — the physics side of the same year.
Name one change where you could tell a new substance formed.
One card at a time — tap “Show me” to check yourself, then Next. Start at Foundation; when those feel easy, climb.
Helpful Hints
🪜 Matter and reactions — the ladder
Protons name the element; valence electrons do the chemistry → the periodic table is the electron shells laid out: a period is one more shell, a group is the same outer shell, so position predicts behavior → metal gives to nonmetal (ionic), nonmetals share (covalent), metals pool (metallic), and each type shows in melting point, conduction and shine → a reaction rearranges atoms into new substances → atoms are conserved, so balance with coefficients and never touch subscripts → mass is conserved — if it looks lost, a gas left the scale.
Position predicts bond; bond predicts property; atoms are conserved.
🤝 The whole idea
Everything an element does comes from its outer electrons, and the periodic table is a seating chart of outer electrons. Read the seat, and you can predict the bond, the properties and the reaction before you ever touch the sample.
The table is the prediction.
⚠️ Tricky ones
NEVER change a subscript to balance. H₂O₂ is a different substance from H₂O. Change coefficients only.
Mass that seems to vanish is a GAS that left. Mass that seems to appear came FROM the air (rust).
Isotopes differ in NEUTRONS. Ions differ in ELECTRONS. Protons never change without a new element.
Down a GROUP: same valence electrons, same chemistry. Across a PERIOD: one more electron each step.
Ionic compounds conduct only when MELTED or DISSOLVED — a salt crystal on the table doesn’t.
Dissolving is PHYSICAL. Burning, rusting, baking are CHEMICAL. Ask: is there a new substance?
🔗 The three bond types — the chart
Bond
Who
What the electrons do
Properties
Examples
ionic
metal + nonmetal
transferred; opposite ions lock in a lattice
hard, brittle, high melting; conducts only melted or dissolved
NaCl, MgO, CaF₂
covalent
nonmetal + nonmetal
shared in pairs; separate molecules
low melting, often soft or gas; most don’t conduct
H₂O, CO₂, CH₄, sugar
metallic
metal + metal
pooled in a shared sea
conducts heat and electricity, bends, shines
copper, iron, brass, steel
Find the two elements on the table; the row picks itself.
🎯 How the test will ask
A blank periodic table with letters — “which is a halogen? a noble gas? most reactive metal?”
“Predict the bond type between elements X and Y and explain using valence electrons.”
An unbalanced equation — “balance it and show the atom counts.”
Before/after masses for a reaction — “explain the difference” (a gas escaped).
A property list — “classify the substance as ionic, covalent or metallic.”
“How many atoms of each element are in 3Ca(OH)₂?”
✅ Can you…
Locate the alkali metals, halogens, noble gases, transition metals and metalloids on a blank table?
Predict a bond type from two positions on the table?
Classify a substance from its melting point and conduction?
Balance an equation with the LCM trick and never touch a subscript?
Explain a mass change with a gas that left or arrived?
Count atoms in a formula with parentheses and a coefficient?
Pick your level
Look back at anything you missed — the hint that appeared is exactly what to reread tonight.
How sure did you feel?
Lab
Work like a scientist: label the diagrams, turn the table into a graph, then write a claim with evidence and reasoning. Every lab checks itself on the spot, and hints are free.
Your practice never leaves this device. There is no account and no sign-in. Your work is saved in this browser only, and you can erase it whenever you want.
Your practice record — saved on this device
This is your record of the module on screen — it stays here and goes nowhere. Independent means you got it right on the first tap; supported means you got it after the explain-and-retry, or marked ‘I had it’ on a revealed answer. Both count, and neither is a grade. If your teacher asks, copy the row or show them this screen.
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The answer key is for a teacher: it prints only from here, for the unit on screen. Print the study packet prints the study pages and a blank quiz — never the answers.