JCE General Science (Syllabus 43) cheat sheet

Investigation order: question, hypothesis, controlled procedure, data collection, analysis, conclusion; the independent variable is changed, the dependent variable is measured, and control variables are kept constant.

Accuracy is closeness to the accepted value; precision is closeness of repeated readings to each other; random error affects precision, while systematic error shifts accuracy.

Mean = sum of values / number of values; range = largest value - smallest value; repeat trials and average to reduce the effect of random variation.

Percentage error = |measured value - accepted value| / accepted value x 100%; percentage difference compares two measured values.

SI base units: metre (length), kilogram (mass), second (time), kelvin (temperature), ampere (current), mole (amount), candela (luminous intensity).

Conversions: 1 cm3 = 1 mL; 1 dm3 = 1 L; 1 kg = 1000 g; 0 degrees C = 273 K; 1 kPa = 1000 Pa.

Graph choice: line graph for continuous numerical data; bar chart for categories; scatter graph to test correlation; pie chart for parts of a whole.

Valid conclusion rule: state whether data support the hypothesis, quote relevant values, and identify sources of error; correlation does not prove causation.

Cell structures: nucleus contains genetic material and controls activity; mitochondria release energy by respiration; chloroplasts carry out photosynthesis; ribosomes make proteins; vacuole stores sap.

Photosynthesis: carbon dioxide + water -> glucose + oxygen, using light energy absorbed by chlorophyll; balanced: 6CO2 + 6H2O -> C6H12O6 + 6O2.

Aerobic respiration: glucose + oxygen -> carbon dioxide + water + energy; anaerobic respiration in muscles produces lactic acid and less energy.

Diffusion moves particles from high to low concentration; osmosis moves water across a partially permeable membrane from high to low water concentration; active transport uses energy to move substances against a concentration gradient.

Enzymes are protein catalysts with a specific active site; reaction rate is highest at optimum temperature and pH, and enzymes denature at high temperature or extreme pH.

Food tests: starch with iodine gives blue-black; reducing sugar with Benedict's solution and heat gives brick-red; protein with Biuret reagent gives purple; lipid emulsion test gives a white emulsion.

Blood vessels: arteries carry blood away from the heart at high pressure; veins carry blood toward the heart at low pressure and have valves; capillaries allow exchange through thin walls.

Genetics: DNA bases pair A with T and C with G; dominant alleles are expressed with one copy, recessive alleles require two; mitosis produces identical cells, meiosis produces gametes with half the chromosome number.

Particle model: solids have fixed shape and volume; liquids have fixed volume but flow; gases fill their container; heating increases particle kinetic energy and usually causes expansion.

Atomic structure: protons have charge +1 and mass 1; neutrons have charge 0 and mass 1; electrons have charge -1 and negligible mass; atomic number = protons; mass number = protons + neutrons.

Periodic table: elements are ordered by increasing atomic number; groups are vertical columns with similar outer-shell electrons; periods are horizontal rows.

Chemical change produces new substances and is usually difficult to reverse; physical change alters state, shape, or size without producing a new substance.

Conservation of mass: in a closed system, total reactant mass equals total product mass; balanced equations have equal numbers of each type of atom on both sides.

pH scale: pH < 7 acidic, pH = 7 neutral, pH > 7 alkaline; acid + base -> salt + water; acids release hydrogen ions in water and alkalis release hydroxide ions.

Separation decision: filtration removes insoluble solids; evaporation crystallises a dissolved solid; simple distillation separates a solvent from a solution; chromatography separates dissolved coloured substances.

Reaction rate increases with higher temperature, higher concentration, greater surface area, and a catalyst; a catalyst lowers activation energy without being consumed.

Speed = distance / time; velocity is speed in a stated direction; acceleration = change in velocity / time; deceleration is negative acceleration.

Balanced forces give zero resultant force, so no acceleration; unbalanced forces cause acceleration in the direction of the resultant force.

Weight = mass x gravitational field strength (W = mg); mass is in kilograms, weight in newtons, and g is about 9.8 N/kg on Earth.

Energy conservation: energy is transferred or transformed but not created or destroyed; kinetic energy = 1/2 mv2; gravitational potential energy = mgh.

Work = force x distance moved in the force's direction; power = work / time; efficiency = useful output energy / total input energy x 100%.

Ohm's law: V = IR; series circuits share current and sum voltage; parallel circuits share voltage and sum current; electrical power = VI.

Wave equation: speed = frequency x wavelength; transverse waves vibrate perpendicular to travel; longitudinal waves vibrate parallel to travel.

Heat transfers from hotter to colder regions by conduction (solids), convection (fluids), and radiation (no medium needed); thermal equilibrium occurs when temperatures equalise.

Earth's structure: crust, mantle, outer core, inner core; the lithosphere is broken into tectonic plates that move on the softer asthenosphere.

Rock types: igneous forms from cooled magma or lava; sedimentary forms from deposited and cemented sediments; metamorphic forms when existing rock is changed by heat and pressure.

Water cycle processes: evaporation, transpiration, condensation, precipitation, runoff, infiltration, and collection; solar energy and gravity drive the cycle.

Carbon cycle: photosynthesis removes carbon dioxide; respiration, decomposition, and combustion release it; oceans and fossil fuels store carbon.

Greenhouse gases include carbon dioxide, methane, nitrous oxide, and water vapour; they absorb infrared radiation and warm the atmosphere.

Renewable resources are replenished faster than use (solar, wind, hydro, biomass); non-renewable resources such as coal, oil, and natural gas form over very long periods.

Weather is short-term atmospheric conditions; climate is long-term average weather; high pressure generally brings clear, settled weather, and low pressure brings clouds and precipitation.

Technology applications: water treatment uses filtration and disinfection; recycling conserves materials and energy; renewable energy systems convert sunlight, wind, or flowing water into electricity.