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Revision Notes & Formula Sheets

Printable summaries for MYP Sciences - key formulas, definitions, and revision points.

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Mechanics

Key Formulas
F = ma
Force (N)
W = Fd
Work done (J)
KE = ½mv²
Kinetic energy (J)
GPE = mgh
Gravitational PE (J)
p = mv
Momentum (kg m/s)
s = d / t
Speed (m/s)
a = Δv / t
Acceleration (m/s²)
W = mg
Weight (N)
Key Definitions
  • Speed - distance travelled per unit time (scalar)
  • Velocity - displacement per unit time (vector - has direction)
  • Acceleration - rate of change of velocity
  • Newton's 1st Law - an object stays at rest or constant velocity unless acted on by an unbalanced force
  • Newton's 2nd Law - F = ma; force equals mass times acceleration
  • Newton's 3rd Law - every action has an equal and opposite reaction
  • Conservation of momentum - total momentum before = total momentum after (in a closed system)
  • Conservation of energy - energy cannot be created or destroyed, only transferred

Electricity

Key Formulas
V = IR
Ohm's law (V)
P = IV
Power (W)
P = I²R
Power (W)
Q = It
Charge (C)
E = Pt
Energy (J)
E = QV
Energy (J)
Series vs Parallel
PropertySeriesParallel
CurrentSame through all componentsSplits at junctions, total = sum of branches
VoltageShared (splits across components)Same across all branches
ResistanceRtotal = R1 + R2 + ...1/Rtotal = 1/R1 + 1/R2 + ...
Key Definitions
  • Current (I) - rate of flow of charge, measured in amperes (A)
  • Voltage (V) - energy transferred per unit charge, measured in volts (V)
  • Resistance (R) - opposition to current flow, measured in ohms (Ω)
  • Direct current (DC) - current flows in one direction only
  • Alternating current (AC) - current reverses direction periodically

Waves

Key Formulas
v = fλ
Wave speed (m/s)
T = 1 / f
Period (s)
EM Spectrum (increasing frequency)
Wave TypeUse
RadioTV, radio broadcasting
MicrowaveCooking, satellite communication
InfraredThermal imaging, remote controls
Visible lightSight, fibre optics
UltravioletSterilisation, sun tanning
X-raysMedical imaging, security scans
Gamma raysCancer treatment, sterilisation
Key Concepts
  • Transverse waves - oscillation perpendicular to direction of travel (e.g. light, water waves)
  • Longitudinal waves - oscillation parallel to direction of travel (e.g. sound)
  • Reflection - angle of incidence = angle of reflection
  • Refraction - change in speed (and direction) when a wave enters a different medium
  • Diffraction - waves spread out when passing through a gap or around an obstacle
  • All EM waves travel at 3 × 108 m/s in a vacuum

Thermal Physics

Key Formulas
Q = mcΔT
Specific heat capacity
Q = mL
Latent heat
Key Definitions
  • Specific heat capacity (c) - energy needed to raise 1 kg of a substance by 1°C (J/kg°C)
  • Specific latent heat (L) - energy needed to change the state of 1 kg without changing temperature
  • Latent heat of fusion - energy for solid ↔ liquid change
  • Latent heat of vaporisation - energy for liquid ↔ gas change
Heat Transfer Methods
MethodHow It WorksRequires Particles?
ConductionVibrating particles transfer energy to neighboursYes (solids mainly)
ConvectionHot fluid rises, cool fluid sinks - creates a currentYes (fluids only)
RadiationEnergy transferred as infrared electromagnetic wavesNo (works in a vacuum)

Atomic Structure

Subatomic Particles
ParticleRelative MassRelative ChargeLocation
Proton1+1Nucleus
Neutron10Nucleus
Electron1/1836 (≈ 0)−1Electron shells
Key Definitions
  • Atomic number (Z) - number of protons in the nucleus (defines the element)
  • Mass number (A) - protons + neutrons
  • Isotopes - atoms of the same element with different numbers of neutrons
  • Electron configuration - electrons fill shells: 2, 8, 8 (e.g. Na = 2,8,1)
  • Ion - an atom that has gained or lost electrons (charged particle)

Bonding

Types of Bonding
PropertyIonicCovalentMetallic
What happensElectrons transferred (metal → non-metal)Electrons shared (non-metal + non-metal)Sea of delocalised electrons (metal + metal)
Melting pointHighLow (simple); Very high (giant)High
Conductivity (solid)NoNoYes
Conductivity (liquid/dissolved)Yes (ions move)NoYes
Solubility in waterOften solubleUsually insolubleInsoluble
ExampleNaClH2O, CO2Fe, Cu

Stoichiometry & Quantitative Chemistry

Key Formulas
n = m / Mr
Moles = mass / molar mass
c = n / V
Concentration (mol/dm³)
NA = 6.02 × 1023
Avogadro's number
Key Concepts
  • One mole - the amount of substance containing 6.02 × 1023 particles
  • Relative atomic mass (Ar) - weighted mean mass of an atom compared to &frac1;12 of carbon-12
  • Relative formula mass (Mr) - sum of all Ar values in a formula
  • Balancing equations - same number of each type of atom on both sides
  • Limiting reagent - the reactant that is completely used up first, determining the amount of product

Reactivity Series & Metals

Reactivity Series (most → least reactive)
MetalSymbolReaction with WaterReaction with Acid
PotassiumKVigorous (flames)Explosive
SodiumNaVigorousVery vigorous
CalciumCaSteady fizzingVigorous
MagnesiumMgVery slow (steam: vigorous)Vigorous
AluminiumAlReacts if oxide removedModerate
ZincZnOnly with steamModerate
IronFeOnly with steamSlow
CopperCuNo reactionNo reaction
SilverAgNo reactionNo reaction
GoldAuNo reactionNo reaction
  • Mnemonic: Please Stop Calling Me A Zebra, I Can See Giraffes
  • A more reactive metal can displace a less reactive metal from its compound
  • Metals above carbon are extracted by electrolysis; those below by reduction with carbon

Acids & Bases

pH Scale
  • pH 0–6 - Acidic (lower = stronger acid)
  • pH 7 - Neutral
  • pH 8–14 - Alkaline / Basic (higher = stronger alkali)
Key Reactions
  • Neutralisation: Acid + Base → Salt + Water
  • Acid + Metal: Acid + Metal → Salt + Hydrogen
  • Acid + Carbonate: Acid + Carbonate → Salt + Water + CO2
Strong vs Weak
StrongWeak
AcidsFully dissociate (HCl, H2SO4, HNO3)Partially dissociate (CH3COOH, citric acid)
BasesFully dissociate (NaOH, KOH)Partially dissociate (NH3)

Cells

Key Formula
Magnification = Image size / Actual size
Microscopy calculation
Organelle Functions
OrganelleFunctionPlant Only?
NucleusContains DNA; controls cell activitiesNo
Cell membraneControls what enters and leaves the cellNo
CytoplasmJelly-like substance where chemical reactions occurNo
MitochondriaSite of aerobic respiration (releases energy)No
RibosomesSite of protein synthesisNo
Cell wallProvides structural support (made of cellulose)Yes
ChloroplastsSite of photosynthesis (contain chlorophyll)Yes
VacuoleStores cell sap; maintains turgor pressureYes (large, permanent)

Ecology

Key Definitions
  • Producer - organism that makes its own food (photosynthesis)
  • Consumer - organism that eats other organisms for energy
  • Decomposer - breaks down dead organisms, returning nutrients to the soil
  • Food chain - linear sequence showing energy transfer between organisms
  • Food web - interconnected food chains in an ecosystem
  • Trophic level - position of an organism in a food chain
Carbon Cycle (summary)
  • CO2 absorbed by plants during photosynthesis
  • Carbon passed along food chains by feeding
  • CO2 released by respiration (all living organisms)
  • CO2 released by combustion of fossil fuels
  • CO2 released by decomposition of dead organisms
Nitrogen Cycle (summary)
  • Nitrogen fixation - N2 converted to NH3/NH4+ by bacteria (or lightning)
  • Nitrification - NH4+ → NO2− → NO3− by nitrifying bacteria
  • Assimilation - plants absorb nitrates and make proteins
  • Denitrification - NO3− → N2 by denitrifying bacteria (anaerobic)

Bioenergetics

Key Equations
6CO2 + 6H2O → C6H12O6 + 6O2
Photosynthesis (light energy required)
C6H12O6 + 6O2 → 6CO2 + 6H2O
Aerobic respiration (releases energy)
C6H12O6 → 2C2H5OH + 2CO2
Anaerobic respiration (in yeast)
Limiting Factors of Photosynthesis
  • Light intensity - more light = faster rate (up to a point)
  • CO2 concentration - more CO2 = faster rate (up to a point)
  • Temperature - increases rate until enzymes denature (~40–45°C)
  • At any time, the factor in shortest supply is the limiting factor
Aerobic vs Anaerobic Respiration
AerobicAnaerobic
OxygenRequiredNot required
Energy releasedLarge amountSmall amount
ProductsCO2 + H2OLactic acid (animals) or ethanol + CO2 (yeast)
LocationMitochondriaCytoplasm

Inheritance & Evolution

Key Definitions
  • DNA - deoxyribonucleic acid; double helix molecule that carries genetic information
  • Gene - a section of DNA that codes for a specific protein
  • Allele - a version of a gene (e.g. brown eyes vs blue eyes)
  • Genotype - the combination of alleles an organism has (e.g. Bb)
  • Phenotype - the observable characteristic (e.g. brown eyes)
  • Dominant - allele expressed when one or two copies present (capital letter)
  • Recessive - allele only expressed when two copies present (lowercase)
  • Homozygous - two identical alleles (BB or bb)
  • Heterozygous - two different alleles (Bb)
Punnett Square Example (Bb × Bb)
Bb
BBBBb
bBbbb
  • Ratio: 3 dominant phenotype : 1 recessive phenotype
  • Genotype ratio: 1 BB : 2 Bb : 1 bb
Natural Selection (4 steps)
  • 1. Variation - individuals in a population show genetic variation
  • 2. Competition - organisms compete for limited resources (food, mates, territory)
  • 3. Survival - individuals with advantageous traits are more likely to survive
  • 4. Reproduction - survivors pass on their advantageous alleles to offspring