The particle model gets an upgrade. Particles are atoms of different types, atoms join into compounds, and a chemical change makes new substances. Concept tutorials with atom-level simulations.
Each lesson works two ways. Students can work through the online tutorial at their own pace (it checks their answers and saves their progress in their browser), or you can teach it to the whole class from the slides, then send students into the tutorial for the Modify and Make steps.
Every lesson guide has plain-language notes, the answers to every check, a solution for every task, and slides and a worksheet for Waypoints Prepare. These guide pages are not linked from student pages, but they are not secret either: keep printed Teacher editions for answers you do not want students to find.
Particles are atoms; atom type decides the element; different atom types chemically joined make a compound (AC9S8U06).
In Year 7 every particle was just "a particle". Now the particles get an identity: they are atoms, and atoms come in about 118 types, one for each element (hydrogen, oxygen, carbon…). All atoms of one element are the same type.
A formula tells you the atom types and how many of each: H₂O has 2 H and 1 O. The small number belongs to the atom before it.
An element is a pure substance of only one type of atom; its particles may be single atoms (He) or joined (O₂, O₃). Symbols are one capital letter or a capital and a small letter (Co is cobalt, CO is carbon monoxide). Misconceptions: pure means element; an element's particles must be single atoms.
A mixture is substances mingled, not joined: properties kept, any amounts, separated physically. A formula gives atom types and numbers (the small number counts the atom before it; a big number counts particles); structural formulas show joins, models show shape. No representation shows everything.
Optional ideas if you run a practical for this unit: pick one, adapt it to your equipment, or use your own.
Safety and ethics: salt and ice can drop below −10 °C; handle the cup, not the slush, and keep filings away from eyes.
A chemical change makes a new substance: atoms rearrange into new particles (AC9S8U07).
A chemical change makes at least one new substance. At the particle level, the atoms in the starting substances (the reactants) separate and join up in new arrangements (the products). No atoms are made or lost; they are rearranged.
A physical change (melting, boiling, dissolving, cutting) changes the arrangement or spacing of the particles, but every particle stays the same particle: no new substance.
The test is "is there a new substance?", not "can it be reversed?" Dissolving salt can be reversed by evaporating the water, and it is physical. Some chemical changes can be reversed too (charging a battery). Reversibility is a clue, not the test.
A colour change, a gas given off (bubbles), a solid forming in a liquid, light, or a temperature change that keeps going. Each is a clue only: boiling water makes bubbles and is physical.
The unit now opens with physical change (node 1): melting, boiling and dissolving rearrange the same particles, so no new substance forms and the mass stays the same. Steam is still H₂O. Chemical change (node 2) then contrasts with it on the same boards.
Signs of a chemical change (colour, gas, precipitate, light, smell, temperature change) are clues, not proof; the test is a new substance. Exothermic reactions give energy out to the surroundings (hotter); endothermic ones take it in (colder). There is no 'cold energy'.
On screen: the short tutorial Physical or chemical? Use all the clues covers node 6 with sorting and misleading-clue cases.
Optional ideas if you run a practical for this unit: pick one, adapt it to your equipment, or use your own.
Safety and ethics: safety glasses with vinegar; gloves for steel wool, which splinters.