TERM 2 · MATTER AND MATERIALSMATTER AND CLASSIFICATION
What you must be able to do
Match a material's properties to its use
Classify and draw mixtures, elements and compounds
Test purity by melting point, boiling point and chromatography
Write names and formulae of compounds
Classify metals, metalloids, non-metals, conductors and magnetic materials
Core content · Properties of materials
Learn each property with a use: strength, brittle or malleable (sheets), ductile (wire), density, melting and boiling point. Class tests: label reading, sorting, chromatography, conductivity, heat, magnets.
Worked example · Give the property that suits each use: copper wiring, aluminium aircraft bodies, tungsten bulb filaments. (3)
✓: copper: ductile and a good electrical conductor
✓: aluminium: strong but low density
✓: tungsten: very high melting point
Core content · Mixtures: homogeneous and heterogeneous
A mixture's substances are not chemically bonded, so it separates physically. Homogeneous: uniform composition, one phase (salt water, air, brass). Heterogeneous: composition varies, parts visible (sand in water, granite).
⚠️ COMMON MISTAKE Air is a mixture, not a compound: its gases are not bonded and their ratio varies. “Pure” on a juice label means nothing added; juice is still a mixture.
Core content · Pure substances: elements, compounds and purity
⚡ MUST MEMORISEElement: a pure substance that cannot be broken down into simpler substances by chemical means. Compound: a pure substance of two or more different elements chemically bonded in a fixed ratio. Pure substance: matter with a fixed composition, made of one kind of particle.
⚖️ LAWS / FRAMEWORKS A pure substance melts and boils at one fixed temperature and gives one spot on a chromatogram. Impurities lower the melting point and spread it over a range.
Worked example · Classify as element, compound, homogeneous or heterogeneous mixture: Cu, CO₂, salt water, muddy water. (4)
✓: Cu: element, one kind of atom
✓: CO₂: compound, C and O bonded in a fixed 1 : 2 ratio
✓: salt water: homogeneous mixture, uniform, salt invisible
“Give a reason” doubles the marks; the reason is the definition.
Worked example · A solid melts between 74 °C and 78 °C; the pure compound melts at 80 °C. Is the sample pure? Explain. (2)
✓: No, it is impure.
✓: It melts over a range, below the fixed melting point of the pure compound.
⭐ EXAM FAVOURITE Sorting a list into elements, compounds and mixtures: nearly every sitting.
Core content · Names and formulae of compounds
Cation first, then anion. -ide: one element (chloride Cl⁻, oxide O²⁻). -ate and -ite contain oxygen, -ate one O more (sulphate SO₄²⁻, sulphite SO₃²⁻). Two non-metals take prefixes: mono-, di-, tri- (carbon dioxide, CO₂). Charges total zero; the ion table is on the reference sheet.
Worked example · Write formulae for calcium chloride and aluminium sulphate; name KNO₃ and SO₂. (4)
Swap the charge numbers, then simplify: Mg²⁺ and O²⁻ give MgO, not Mg₂O₂.
⚠️ COMMON MISTAKE Brackets go round a polyatomic ion used more than once: Ca(OH)₂, never CaOH₂. Ionic compounds take no prefixes: MgCl₂ is magnesium chloride, not magnesium dichloride.
Core content · Metals, metalloids and non-metals
Metals sit left of the staircase: shiny, malleable, ductile, conductors. Non-metals sit right, with hydrogen: dull, brittle, insulators (graphite conducts). Metalloids (B, Si, Ge, As) on the staircase are mostly non-metallic semiconductors.
⚠️ COMMON MISTAKE A metalloid conducts better when heated; a metal conducts worse. “Both improve” loses the mark.
💡 EASY MARK Find the element on the data-sheet periodic table and know where the staircase runs (B, Si, Ge, As, Sb, Te): “metal or non-metal?” is then free.
Core content · Conductors, insulators and magnetic materials
Electrical: conductors (metals, graphite) wire circuits; semiconductors (Si, Ge) make chips and solar cells; insulators (plastic, rubber) coat cables.
Thermal: metals conduct (pot bases); wood, polystyrene and air insulate (handles, cooler boxes).
Magnetic: iron, cobalt, nickel and steel are attracted. Magnets sort scrap and drive compasses, motors, speakers.
⚠️ COMMON MISTAKE Not every metal is magnetic: copper, aluminium and gold are not attracted, so “all metals stick to magnets” loses the mark.
🧠 ACTIVE RECALL
Which statement correctly defines an element?
Complete the sentence: a compound is a pure substance of ...
Choose the words that complete the CAPS definition: ‘A pure substance is matter with ...’
Which statement is true of every mixture?
A learner must define a homogeneous mixture. Which answer earns the mark?
A teacher writes four substances on the board: copper wire (Cu), carbon dioxide (CO₂), air and nitrogen gas (N₂). Which one is a compound?
A particle diagram shows a container holding only one kind of particle. Every particle is two identical atoms joined together. How is the substance classified?
A second diagram shows separate pairs of oxygen atoms (O₂) and separate pairs of nitrogen atoms (N₂), spread evenly in a container. There are no bonds between an oxygen pair and a nitrogen pair. How is the contents classified?
Mpho stirs salt into water until no crystals can be seen. How should the liquid be classified?
A carton of orange juice is labelled ‘100% pure, nothing added’. How does Physical Sciences classify the juice?
A white solid starts to melt at 118 °C and is completely liquid at 123 °C. The pure compound melts at 125 °C. What can be concluded about the sample?
Black ink is separated by paper chromatography. Three spots appear at different heights on the paper. What does the chromatogram show?
Two liquids are heated. Liquid X boils at one steady temperature, 78 °C. Liquid Y begins to boil at 90 °C and the thermometer reading creeps up to 96 °C before it has all boiled away. Which conclusion is best supported by the evidence?
A pure compound melts at exactly 80 °C. Four samples of it are heated. P melts at 80 °C. Q melts from 76 °C to 79 °C. R melts from 78 °C to 80 °C. S melts from 68 °C to 72 °C. Which sample is most likely to be pure?
A dye gives only one spot when it is run on a chromatogram. Which conclusion is justified?
Aluminium forms Al³⁺ ions and oxygen forms O²⁻ ions. What is the formula of aluminium oxide?
Calcium forms Ca²⁺ ions and the nitrate ion is NO₃⁻. Which formula for calcium nitrate is written correctly?
What is the correct name of the compound with the formula K₂SO₃?
Sulphur and oxygen are both non-metals. Which name is correct for the compound SO₃?
Which formula and name are correctly matched?
A learner tests an unknown solid. It is dull and brittle, and it does not conduct electricity when cold or when heated. How is it classified, and where on the periodic table does it sit?
A copper wire (Cu) and a germanium rod (Ge) are each connected in a circuit with an ammeter. Both are warmed gently. How does the current change in each?
An element is shiny but brittle, sits on the staircase and is used to make computer chips. Which of these could it be?
A learner argues: ‘Anything that conducts electricity must be a metal.’ Which fact shows that the argument is wrong?
Four elements are tested. P is shiny and malleable, and the current through it falls as it is heated. Q is dull and brittle, and it never conducts. R is shiny and brittle, and it conducts little when cold but more when hot. S is shiny and ductile and not magnetic, and the current through it falls as it is heated. Which element is the metalloid?
A designer is evaluating a kettle. The handle must stay cool and the base must heat the water quickly. Which choice of materials is best justified?
An electrician is choosing a cable to carry current through a house wall. Which design is best justified?
A recycling plant plans to use a strong magnet to pull the copper pipes and aluminium cans out of a pile of rubber, glass and wood. Which evaluation of the plan is correct?
A company designs a cooler box to keep drinks cold on a hot day. It has polystyrene walls and an aluminium lid. Which improvement is best justified?
A designer needs a metal for the filament of a light bulb, which reaches about 2 500 °C. The melting points are tungsten 3 422 °C, copper 1 085 °C, aluminium 660 °C and zinc 420 °C. Which choice is best justified?
Define the term compound. (2)
A pure substance of two or more different elementsThe definition starts with what a compound is made of: more than one kind of element, in a pure substance.
that are chemically bonded together in a fixed ratioThe examiner listens for the bond and the fixed ratio. These two ideas separate a compound from a mixture.
A compound is a pure substance of two or more different elementsthat are chemically bonded together in a fixed ratio.
Classify each substance as an element, a compound, a homogeneous mixture or a heterogeneous mixture, and give a reason for each: (a) iron (Fe), (b) sulphur dioxide (SO₂), (c) brass, (d) granite. (4)
Iron is an element: one kind of atom, cannot be broken down chemicallyAn element is a pure substance that cannot be broken down chemically, so the reason is one kind of atom.
Sulphur dioxide is a compound: sulphur and oxygen bonded in a fixed 1 : 2 ratioThe reason is the definition: different elements chemically bonded in a fixed ratio.
Brass is a homogeneous mixture: uniform composition, parts cannot be seen separatelyHomogeneous means a uniform composition in which the parts cannot be seen separately.
Granite is a heterogeneous mixture: composition varies, different parts can be seenHeterogeneous means the composition varies and different parts are visible.
(a) Iron is an element: it is a pure substance made of one kind of atom that cannot be broken down chemically.(b) Sulphur dioxide is a compound: sulphur and oxygen are chemically bonded in a fixed 1 : 2 ratio.(c) Brass is a homogeneous mixture: its metals are not chemically bonded and the composition is uniform throughout.(d) Granite is a heterogeneous mixture: its composition varies and the different minerals can be seen.
A food-colouring powder is sold as a ‘pure red dye’. The pure red dye melts at exactly 165 °C. A chromatogram of the powder shows two spots. (a) Is the powder a pure substance? Give a reason that refers to the chromatogram. (2) (b) Predict how the powder will melt compared with the pure dye. (2) (4)
No, the powder is not pure: it is a mixtureThe conclusion has to be stated: the powder is a mixture, not a pure substance.
Two spots show at least two different substances; a pure substance gives one spotThe reason must come from the chromatogram: a pure substance gives one spot, so two spots mean two substances.
It will melt over a range of temperatures, not at one fixed temperatureImpurities spread the melting over a range. A pure substance melts at one fixed temperature.
It will begin to melt below 165 °CImpurities lower the melting point, so melting starts below the 165 °C of the pure dye.
(a) No, the powder is not a pure substance; it is a mixture.The chromatogram has two spots, so there are at least two different substances, because a pure substance gives only one spot.(b) The powder will melt over a range of temperatures instead of at one fixed temperature,and it will begin to melt below 165 °C, because impurities lower the melting point.
Explain to a Grade 8 learner why air is a mixture and not a compound, even though it contains both oxygen and nitrogen.
Explain to a Grade 8 learner how a chromatogram can show that a black ink is not a pure substance.
Explain to a Grade 8 learner how the staircase on the periodic table helps you decide whether an element is a metal, a metalloid or a non-metal.
ONE-MINUTE SUMMARY Matter is a mixture (homogeneous or heterogeneous) or a pure substance (element or compound); purity shows as a sharp melting point and one chromatogram spot. Names run cation then anion; position gives metal or non-metal.
IN THE EXAM
Paper 2: 2 to 10 marks per sitting, in Question 1 multiple choice and one data-table question.
Expect a list to classify, often with “give a reason” for the second mark.
Names and formulae return in bonding, equations and the mole.
🔒 STATES
🔒 ATOM
🔒 PERIODIC TABLE
🔒 BONDING
🔒 CHANGE
🔒 EQUATIONS
🔒
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Feeling the pressure? Take a breath.
Exam stress is completely normal. Here are a few things that actually work. None of this replaces a doctor or a trusted adult.
Breathe in
Box breathing: 4 counts in, 4 hold, 4 out, 4 hold. Do it four times.
Anxiety
Grounding: name 5 things you see, 4 you hear, 3 you can touch.
Reframe "I am going to fail" into "I have prepared, I will do my best".
Concentration
Work in 25-minute blocks, then a 5-minute break (Pomodoro).
Put the phone in another room while you study.
One task at a time. Multitasking costs more than it saves.
Sleep
Cramming all night backfires: sleep is when the brain locks in memory.
No screens for 30 minutes before bed.
The same bedtime every night keeps the brain sharp.
Study habits
Active recall (testing yourself) beats passive re-reading by far.
Space your study across days; do not cram it all into one.
Practise past papers under time. That is exactly how these notes are built.
If it gets too much, talk to a parent, teacher or a trusted adult. You do not have to carry it alone. SADAG (free, 24 hours): 0800 567 567, or SMS 31393.