OAE Integrated Science cheat sheet

Scientific method cycle: observation → question → hypothesis → controlled experiment → data analysis → conclusion → peer review → replication; conclusions can revise the hypothesis at any step.

Independent variable = factor deliberately changed; dependent variable = measured response; controlled variables held constant; a control group receives no treatment to establish baseline.

Validity vs. reliability: validity means the test measures what it claims; reliability means repeated trials give consistent results. A test can be reliable but invalid.

Hypothesis must be testable and falsifiable; a theory is a well-supported explanation unifying many observations, not a guess; a law describes a consistent relationship.

Significant figures: nonzero digits count; zeros between nonzero digits count; leading zeros never count; trailing zeros count only with a decimal point.

Metric conversions: kilo- 10³, centi- 10⁻², milli- 10⁻³, micro- 10⁻⁶, nano- 10⁻⁹; 1 mL = 1 cm³; density = mass/volume (g/cm³ or g/mL).

Accuracy = closeness to true value; precision = closeness of repeated measurements to each other; percent error = |measured − accepted| / accepted × 100.

Bias controls: random sampling, blind and double-blind designs, placebo, large sample size, and repetition reduce systematic and sampling error.

Scientific models are simplified representations; they are revised when new evidence conflicts, e.g., atomic models from Dalton to quantum mechanical.

Newton's laws: (1) inertia - objects resist changes in motion; (2) F = ma; (3) every action has an equal and opposite reaction. Weight = mg (g ≈ 9.8 m/s²).

Kinematics: v = v₀ + at; d = v₀t + ½at²; v² = v₀² + 2ad. Acceleration due to gravity near Earth is about 9.8 m/s² downward, independent of mass (ignoring air resistance).

Work = force × distance (joules); power = work/time (watts); kinetic energy = ½mv²; gravitational potential energy = mgh; conservation of energy holds in closed systems.

Ohm's law V = IR; power P = IV = I²R = V²/R; series circuits share current and sum resistance, parallel circuits share voltage and add reciprocals of resistance.

Waves: speed = frequency × wavelength (v = fλ); transverse waves (light) oscillate perpendicular to travel; longitudinal waves (sound) oscillate parallel; sound needs a medium, light does not.

Atomic structure: protons (+1, atomic number), neutrons (0, mass number − atomic number), electrons (−1) in energy levels; isotopes differ in neutrons only.

Bonding: ionic bonds transfer electrons between metals and nonmetals; covalent bonds share electrons between nonmetals; metallic bonds share a sea of delocalized electrons.

Chemical reactions: reactants → products; balancing conserves atoms; types include synthesis, decomposition, single replacement, double replacement, and combustion.

Acids donate H⁺ (pH < 7), bases accept H⁺ or donate OH⁻ (pH > 7); pH = −log[H⁺]; neutralization produces salt and water.

Cell theory: all living things are made of cells, cells are the basic unit of life, and all cells come from pre-existing cells.

Prokaryotes lack a membrane-bound nucleus and organelles; eukaryotes have a nucleus and membrane-bound organelles (mitochondria, chloroplasts, ER, Golgi).

Photosynthesis: 6CO₂ + 6H₂O + light → C₆H₁₂O₆ + 6O₂, occurs in chloroplasts; cellular respiration: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP, occurs in mitochondria.

Mitosis produces two identical diploid cells for growth and repair; meiosis produces four genetically varied haploid gametes with crossing over and independent assortment.

DNA structure: double helix of nucleotides (sugar, phosphate, nitrogenous base); base pairing A–T and G–C; transcription makes mRNA, translation at ribosomes builds protein.

Mendelian genetics: dominant alleles mask recessive; genotype is allele combination, phenotype is observable trait; Punnett squares predict offspring ratios.

Natural selection requires heritable variation, differential reproductive success, and environmental pressure over generations; it acts on populations, not individuals.

Ecology: producers → consumers → decomposers; energy decreases about 90% per trophic level (10% rule); food webs show interconnected food chains.

Homeostasis maintains stable internal conditions via feedback loops; negative feedback reverses change (e.g., insulin lowering blood glucose), positive feedback amplifies it.

Earth's layers: crust (thin, silicate), mantle (convection drives plate motion), outer core (liquid iron, generates magnetic field), inner core (solid iron-nickel).

Plate tectonics: divergent boundaries create new crust (mid-ocean ridges), convergent boundaries cause subduction and mountain building, transform boundaries cause earthquakes.

Rock cycle: igneous forms from cooling magma/lava, sedimentary from compaction and cementation of sediments, metamorphic from heat and pressure; any rock can transform into any other.

Water cycle: evaporation, transpiration, condensation, precipitation, runoff, infiltration, and groundwater flow; the Sun is the energy source.

Weather vs. climate: weather is short-term atmospheric state; climate is long-term average. Air masses and fronts (cold, warm, stationary, occluded) drive weather changes.

Earth–Moon–Sun geometry causes tides (spring tides at new and full moons, neap tides at quarter moons) and eclipses (solar at new moon, lunar at full moon).

Seasons result from Earth's 23.5° axial tilt, not distance from the Sun; solstices mark maximum tilt toward or away from the Sun, equinoxes equal day and night.

Solar system order: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune; inner planets are rocky, outer planets are gas/ice giants; asteroids lie mainly between Mars and Jupiter.

Moon phases cycle about 29.5 days: new → waxing crescent → first quarter → waxing gibbous → full → waning gibbous → third quarter → waning crescent.