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LOWER SEC SCIENCE SEC 1

Sec 1 Chemistry
Visual Notes

Pictures first. Formulas boxed. Every exam keyword highlighted.
HOW TO STUDY WITH THIS
Read the 💡 box
the whole topic in 1 line
Study the diagram
cover it, redraw it
Learn the yellow
formulas & keywords
Redo the worked example
without looking
THE CHAPTERS
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CH 1
Properties of Matter
Density = mass ÷ volume.
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CH 2
Elements, Compounds, Mixtures
Chemically joined or not?
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CH 3
Separation Techniques
Match the method to the mixture.
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CH 4
Solutions & Suspensions
Dissolves = solution.
📌 NOTESchools order Lower Sec Science differently — some teach these chapters in Sec 2.
🖨 PRINTCtrl+P → Save as PDF · Scale 100% · Margins None · Background graphics ON
Chemistry · Sec 1 (Lower Sec Science)
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1

Physical Properties of Matter

strength, hardness, conductivity, density
BIG IDEAEvery material has physical properties you can measure without changing what it is. density = mass ÷ volume
PropertyMeansMetalsNon-metals
Strengthresists breakingstrongusually weak
Hardnessresists scratchingusually hardvaries
Flexibilitybends without breakingmalleable, ductilebrittle (solids)
Melting / boiling pointtemp it changes statehighusually low
Electrical conductivitylets electricity flowgoodpoor (graphite conducts)
Thermal conductivitylets heat flowgoodpoor (insulators)
⚖️ Density
ρ = m ÷ V
units: g/cm³ or kg/m³
stone: 60 g, 20 cm³ → 3 g/cm³
water = 1 g/cm³: less dense → floats
50 cm³ 70 cm³
irregular object: volume = rise in water = 20 cm³
🧠 HOOKChoose a material by its properties: copper for wires (conducts), plastic for handles (insulator), steel for bridges (strong).
⚠ TRAPDensity of a substance stays the same whatever the size of the piece — a small and big gold bar have the same density.
Chemistry · Sec 1 (Lower Sec Science)
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2

Elements, Compounds & Mixtures

classifying matter
BIG IDEAElement = one type of atom. Compound = elements chemically joined. Mixture = not chemically joined.
ELEMENT
one type of atom
COMPOUND
elements chemically joined, fixed ratio
MIXTURE
not chemically joined — can separate
CompoundMixture
Joined?chemically combinedjust mixed
Proportionfixed (H₂O always 2 : 1)any amount
Propertiesdifferent from its elementskeeps the properties of its parts
Separate bychemical reaction onlyphysical methods (filter, distil…)
Energy changeusually heat/light when formednone
Example
sodium (reactive metal) + chlorine (poisonous gas) → sodium chloride (table salt) — totally new properties
Element groups
metals: shiny, conduct, malleable (Fe, Cu, Al)
non-metals: dull, insulators (C, S, O)
listed in the Periodic Table
✍ WRITE THIS"A compound has different properties from the elements it is made of, and its elements are in a fixed ratio."
Chemistry · Sec 1 (Lower Sec Science)
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3

Separation Techniques

magnetic, filtration, evaporation, distillation, chromatography
BIG IDEAPick the method by what is different about the two substances: size, solubility, boiling point, magnetism.
MethodSeparatesBecause
🧲 Magnetic attractioniron from sand / sulfuronly iron is magnetic
Filtrationinsoluble solid + liquidparticles too big for filter paper
Evaporationdissolved solid (want solid)water boils off
Crystallisationdissolved solid (want pure crystals)crystals form on cooling
Distillationsolvent from a solutiondifferent boiling points
Paper chromatographydyes / inksdifferent solubility
residue filtrate filter paper
Filtration — residue stays on paper, filtrate passes through
water in water out thermometer bulb at side-arm heat distillate condenser
Distillation — cold water enters at the bottom of condenser
mixdye X solventfront pencilbaseline
Chromatography — mix contains dye X (spot at the same height)
💧 Water treatment
screening → sedimentation → filtration → chlorination (kills germs)
NEWater: microfiltration → reverse osmosis → UV disinfection
🌊 Desalination
sea water → drinkable water by distillation or reverse osmosis
Chemistry · Sec 1 (Lower Sec Science)
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4

Solutions & Suspensions

solute, solvent, solubility, rate of dissolving
BIG IDEAsolute + solvent = solution. If it dissolves, you get a clear solution; if not, a cloudy suspension.
solute🧂+ solvent= solution
salt + water = salt solution
SolutionSuspension
Looksclear (may be coloured)cloudy
Settles?noyes, on standing
Filter?passes throughsolid stays on paper
Examplesalt watermuddy water, chalk + water
⚡ Rate of dissolving — faster if…
🔥 solvent is hotter
🥄 you stir
🔨 solute is in smaller pieces (powder)
📈 Solubility
max mass that dissolves in 100 g of solvent at that temperature
most solids: more soluble when hotter
Words
dilute: little solute · concentrated: lots of solute
saturated: can dissolve no more at that temperature
⚠ TRAPStirring makes sugar dissolve faster, but it does NOT make more sugar dissolve — that is solubility, which depends on temperature.
Chemistry · Sec 1 (Lower Sec Science)