NB Grade 8 Scientific Literacy cheat sheet

Independent variable: the factor the experimenter deliberately changes; dependent variable: the factor measured in response; controlled variables are held constant to prevent confounding.

A hypothesis must be testable and falsifiable: it predicts a specific, observable outcome that data could contradict.

Validity vs. reliability: validity means the procedure measures what it claims; reliability means repeated trials give consistent results. Neither guarantees the other.

Control group receives no treatment (or a placebo) and provides the baseline against which the experimental group is compared.

Sample size and repetition: larger samples and multiple trials reduce the effect of random error; a single trial cannot establish a pattern.

Observation vs. inference: observations are direct sensory or instrument readings; inferences are explanations built from those observations.

Metric conversions: 1 km = 1000 m, 1 m = 100 cm = 1000 mm, 1 kg = 1000 g, 1 L = 1000 mL; 1 mL of water has a mass of about 1 g.

Mean = sum of values / number of values; a measurement's precision is set by the smallest division of the instrument, plus one estimated digit.

A conclusion must be limited to the data collected; correlation between two variables does not by itself demonstrate causation.

Cell theory: all living things are made of cells, the cell is the basic unit of structure and function, and all cells arise from existing cells.

Prokaryotic cells lack a membrane-bound nucleus and organelles; eukaryotic cells (plant, animal, fungal, protist) have a nucleus and membrane-bound organelles.

Organelles and jobs: nucleus controls activities and holds DNA; mitochondria release energy from food; ribosomes build proteins; chloroplasts carry out photosynthesis; vacuoles store water and materials; cell membrane controls what enters and exits.

Plant vs. animal cells: plant cells have a cell wall, chloroplasts, and usually one large central vacuole; animal cells have neither wall nor chloroplasts.

Levels of organization: cell to tissue to organ to organ system to organism.

Human body systems: circulatory transports materials, respiratory exchanges gases, digestive breaks down and absorbs nutrients, nervous conducts signals, skeletal and muscular support and move the body.

Mitosis produces two genetically identical body cells for growth and repair; meiosis produces four genetically varied sex cells (gametes) with half the chromosome number.

Sexual reproduction combines gametes from two parents and produces offspring that vary genetically; asexual reproduction involves one parent and yields genetically identical offspring.

In humans, traits are passed on chromosomes; each parent contributes one allele per gene, and dominant alleles mask recessive ones in the heterozygous condition.

Pure substance vs. mixture: a pure substance has fixed composition (element or compound); a mixture's components keep their own properties and can be separated by physical means.

Homogeneous mixture (solution) has uniform composition throughout; heterogeneous mixture has visibly different parts.

Separation techniques: filtration separates solids from liquids; evaporation recovers a dissolved solid; distillation separates liquids by boiling point; magnetism removes iron.

Density = mass / volume (D = m/V); an object denser than its fluid sinks, less dense floats. Water's density is about 1 g/mL.

Particle model explains states: solid particles are closely packed and vibrate in place; liquid particles are close but slide past one another; gas particles are far apart and move rapidly.

Changes of state: melting, freezing, evaporation, condensation, sublimation, deposition; these are physical changes because the substance's identity is unchanged.

Chemical change indicators: new color, gas production, precipitate formation, energy release or absorption, and change not easily reversed.

Conservation of mass: in a closed system, the total mass of reactants equals the total mass of products.

Pressure in a fluid increases with depth and depends on fluid density; buoyant force equals the weight of the displaced fluid.

Speed = distance / time; velocity includes direction; acceleration = change in velocity / time and occurs whenever speed, direction, or both change.

Newton's first law: an object at rest or in uniform motion stays that way unless a net force acts on it (inertia).

Newton's second law: net force = mass x acceleration (F = ma); for a given force, greater mass means less acceleration.

Newton's third law: every action force has an equal and opposite reaction force acting on a different object.

Friction opposes motion between surfaces and converts kinetic energy into thermal energy; gravity pulls masses toward one another, and weight = mass x gravitational field strength.

Work = force x distance (force in the direction of motion); power = work / time; the unit of work and energy is the joule, power is the watt.

Kinetic energy = 1/2 mv^2; potential energy (gravitational) = mgh; energy is conserved but transforms between forms.

Balanced forces produce no change in motion; unbalanced forces produce acceleration in the direction of the net force.

Simple machines (lever, pulley, inclined plane, wheel and axle, wedge, screw) trade force for distance; no machine increases total work output beyond input.

Earth's layers: crust (thin, rocky), mantle (thick, hot, slowly flowing rock), outer core (liquid metal), inner core (solid metal, mostly iron and nickel).

Plate tectonics: the lithosphere is broken into plates that move over the asthenosphere; divergent boundaries create new crust, convergent boundaries cause subduction and mountain building, transform boundaries cause faulting.

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

The rock cycle links the three rock types through melting, cooling, weathering, erosion, deposition, compaction, and metamorphism.

Weathering breaks rock down in place; erosion transports the broken material; deposition lays it down.

Earth's rotation on its axis (about 24 hours) causes day and night; revolution around the Sun (about 365.25 days) with a tilted axis causes the seasons.

Moon phases result from the changing angle between the Sun, Earth, and Moon; a solar eclipse occurs at new moon, a lunar eclipse at full moon.

Solar system order from the Sun: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune; inner planets are rocky, outer planets are gas or ice giants.

Gravity governs orbits: planets orbit the Sun and moons orbit planets; the Sun holds over 99% of the solar system's mass.

Renewable resources (solar, wind, hydro, geothermal, biomass) are replenished on human timescales; nonrenewable resources (coal, oil, natural gas, minerals) are finite.

Burning fossil fuels releases carbon dioxide, a greenhouse gas linked to global climate change and ocean acidification.

Ecosystem impacts: habitat destruction, pollution, and invasive species reduce biodiversity; biodiversity supports ecosystem stability and resilience.

The engineering design cycle: define the problem, research, design, build a prototype, test, evaluate, and redesign; constraints include cost, safety, and materials.

Risk assessment weighs the probability of harm against the severity of harm; a hazard is not the same as a risk.

Technology has trade-offs: a solution that benefits one group or system may create costs elsewhere (e.g., energy production vs. land use).

Sustainable practices include reducing consumption, reusing materials, recycling, conserving water and energy, and using renewable sources.

Scientific evidence informs public decisions, but decisions also involve economic, ethical, and social values; scientific claims should be evaluated by their evidence and reproducibility.