Your FREE Praxis 5005 Flashcards 2026 – 200+ Cards

The continuous process by which rocks change among three types — igneous, sedimentary, and metamorphic — through melting, cooling, weathering, compaction, heat, and pressure.

Rock that forms when molten magma or lava cools and hardens, such as granite (cools slowly underground) and basalt (cools quickly at the surface).

Rock formed when layers of sediment are deposited, compacted, and cemented over time, such as sandstone, limestone, and shale; it often contains fossils.

Rock formed when existing rock is changed by intense heat and pressure without melting, such as marble (from limestone) and slate (from shale).

Molten rock beneath Earth's surface; when it reaches the surface and erupts it is called lava.

The theory that Earth's lithosphere is divided into large plates that slowly move on the asthenosphere, causing earthquakes, volcanoes, and mountain building.

A place where two tectonic plates move toward each other, forming mountains, volcanoes, or deep ocean trenches through collision or subduction.

A place where two tectonic plates move apart, allowing magma to rise and create new crust, such as at a mid-ocean ridge.

A place where two tectonic plates slide past each other horizontally, building stress that is released as earthquakes, such as the San Andreas Fault.

The process by which a denser oceanic plate sinks beneath a lighter plate at a convergent boundary, often forming trenches and volcanoes.

A sudden shaking of the ground caused by the release of energy as tectonic plates shift along a fault; the point underground where it begins is the focus.

An opening in Earth's crust through which magma, gases, and ash erupt; common at plate boundaries and hot spots.

The breaking down of rock into smaller pieces by physical (mechanical) or chemical processes; it does not move the material, unlike erosion.

The physical breakup of rock into smaller pieces without changing its chemical makeup, caused by frost wedging, abrasion, or plant root growth.

The breakdown of rock through chemical reactions, such as acid rain dissolving limestone or oxygen rusting iron-rich minerals.

The movement of weathered rock and soil from one place to another by wind, water, ice, or gravity.

The process by which eroded sediment is dropped and laid down in a new location, building features such as deltas, sandbars, and dunes.

The continuous movement of water through evaporation, condensation, precipitation, and collection, powered by energy from the Sun.

The change of liquid water into water vapor (a gas), driven by heat from the Sun; the first step in the water cycle.

The change of water vapor into liquid droplets, which forms clouds when warm, moist air rises and cools.

Water that falls from clouds to Earth's surface as rain, snow, sleet, or hail when droplets grow too heavy to stay aloft.

The release of water vapor from plants into the atmosphere through their leaves, contributing to the water cycle.

Water stored beneath Earth's surface in the spaces of soil and rock; an aquifer is a layer of rock that holds and transmits it.

An area of land where all the rain and snow drain into a common body of water, such as a river, lake, or ocean.

The day-to-day conditions of the atmosphere in a place, including temperature, precipitation, wind, humidity, and air pressure.

The average weather pattern of a region measured over many years (typically 30 or more), unlike weather, which changes daily.

The amount of water vapor in the air; relative humidity is the percentage of moisture the air holds compared with the maximum it can hold.

The force of air pressing down on Earth's surface; it is measured with a barometer and decreases as altitude increases.

The boundary where two air masses of different temperatures meet; cold fronts often bring storms, while warm fronts bring steady rain.

The layer of gases surrounding Earth, made mostly of nitrogen (about 78%) and oxygen (about 21%), that supports life and moderates temperature.

The lowest layer of the atmosphere, where most weather occurs and where humans and aircraft operate.

The atmospheric layer above the troposphere that contains the ozone layer, which absorbs harmful ultraviolet radiation from the Sun.

A region of the stratosphere rich in ozone that shields Earth's surface from most of the Sun's harmful ultraviolet rays.

The trapping of heat near Earth's surface by atmospheric gases such as carbon dioxide and water vapor, which keeps the planet warm enough for life.

The spinning of Earth on its axis once about every 24 hours, which causes the cycle of day and night.

The movement of Earth around the Sun, which takes about 365.25 days (one year) to complete.

Earth's tilt of about 23.5 degrees relative to its orbit, which causes the seasons as different parts of the planet receive more direct sunlight.

Yearly periods (spring, summer, fall, winter) caused by Earth's tilted axis as it revolves around the Sun, changing the angle and length of sunlight.

One of two days each year (around March 21 and September 22) when day and night are nearly equal in length everywhere on Earth.

One of two days each year with the longest (summer) or shortest (winter) period of daylight, caused by the maximum tilt toward or away from the Sun.

The changing shapes of the lit Moon as seen from Earth — new, crescent, quarter, gibbous, and full — caused by the Moon's orbit and changing sunlight angle.

The phase period when the lit portion of the Moon appears to grow larger each night, moving from new moon toward full moon.

The phase period when the lit portion of the Moon appears to shrink each night, moving from full moon back toward new moon.

An event in which the Moon passes between the Sun and Earth, casting a shadow that blocks the Sun's light; it occurs only during a new moon.

An event in which Earth passes between the Sun and the Moon, casting Earth's shadow on the Moon; it occurs only during a full moon.

The regular rise and fall of ocean water caused mainly by the Moon's gravitational pull, with smaller effects from the Sun.

The Sun and everything bound to it by gravity, including eight planets, dwarf planets, moons, asteroids, and comets.

The four rocky, terrestrial planets closest to the Sun — Mercury, Venus, Earth, and Mars.

The four large gas and ice giants beyond the asteroid belt — Jupiter, Saturn, Uranus, and Neptune.

A region of rocky debris orbiting the Sun between Mars and Jupiter, separating the inner and outer planets.

A small icy body that releases gas and dust to form a glowing tail when its orbit brings it close to the Sun.

A massive ball of hot gas that produces light and heat through nuclear fusion in its core; the Sun is the closest star to Earth.

The star at the center of our solar system, a medium-sized yellow star whose energy from nuclear fusion drives the water cycle, weather, and life on Earth.

A huge system of stars, gas, and dust held together by gravity; Earth lies in the Milky Way galaxy.

A recognizable pattern of stars in the night sky, such as Orion or the Big Dipper, used historically for navigation and storytelling.

A naturally occurring, inorganic solid with a definite chemical composition and crystal structure, such as quartz, feldspar, or calcite.

A scale from 1 (talc) to 10 (diamond) that ranks minerals by their resistance to scratching.

The color of the powder a mineral leaves when rubbed on an unglazed tile; a more reliable identifier than the mineral's surface color.

The preserved remains or traces of a once-living organism, usually found in sedimentary rock, that provide evidence of past life and environments.

A fossil of an organism that lived during a short, well-defined time span, used to date the rock layers in which it is found.

The system that divides Earth's 4.6-billion-year history into eons, eras, periods, and epochs based on major events and rock and fossil records.

The principle that in undisturbed rock layers, the oldest layer is at the bottom and the youngest is at the top.

A natural resource that can be replenished within a human lifetime, such as solar energy, wind, water, and timber.

A natural resource that forms over millions of years and is used faster than it is replaced, such as coal, oil, and natural gas (fossil fuels).

Energy-rich nonrenewable resources — coal, oil, and natural gas — formed from the remains of ancient organisms buried under heat and pressure.

The thin upper layer of Earth made of weathered rock particles, water, air, and decomposed organic matter (humus) that supports plant growth.

A naturally occurring event such as a hurricane, flood, drought, or earthquake that can threaten people and the environment.

The basic structural and functional unit of all living things; organisms may be single-celled or made of trillions of cells.

The thin outer boundary of a cell that controls what enters and leaves, keeping the cell's internal environment stable.

The control center of a eukaryotic cell that contains DNA and directs the cell's activities such as growth and reproduction.

The jelly-like fluid inside a cell where organelles are suspended and many chemical reactions take place.

Organelles known as the cell's 'powerhouses' because they release energy from food through cellular respiration.

An organelle found in plant cells that contains chlorophyll and carries out photosynthesis to make food from sunlight.

A rigid outer layer outside the cell membrane in plant cells (and many bacteria) that provides shape and support; animal cells lack it.

Plant cells have a cell wall, chloroplasts, and a large central vacuole; animal cells have none of these but both have a membrane, nucleus, and cytoplasm.

The process by which plants use sunlight, carbon dioxide, and water to make glucose and oxygen: $\ce{6CO2 + 6H2O ->[\text{light}] C6H12O6 + 6O2}$.

The process by which cells break down glucose with oxygen to release energy: $\ce{C6H12O6 + 6O2 -> 6CO2 + 6H2O}$.

The green pigment in chloroplasts that absorbs light energy to power photosynthesis and gives plants their color.

The system of grouping organisms by shared characteristics, from broadest to most specific: domain, kingdom, phylum, class, order, family, genus, species.

A broad level of biological classification; the commonly taught kingdoms include animals, plants, fungi, protists, and bacteria.

The most specific level of classification; a group of organisms that can interbreed and produce fertile offspring.

An animal with a backbone (spine), including mammals, birds, reptiles, amphibians, and fish.

An animal without a backbone, such as insects, worms, spiders, and jellyfish; they make up most animal species.

A single linear path showing how energy flows as one organism eats another, from producer to consumer to decomposer.

A model of many interconnected food chains showing the complex feeding relationships among organisms in an ecosystem.

A diagram showing that available energy decreases at each higher feeding level, with only about 10% passing from one level to the next.

An organism, usually a plant or alga, that makes its own food through photosynthesis and forms the base of a food chain (an autotroph).

An organism that gets energy by eating other organisms; consumers may be herbivores, carnivores, or omnivores (a heterotroph).

An organism such as a fungus or bacterium that breaks down dead organisms and waste, returning nutrients to the soil.

A consumer that eats only plants, such as a rabbit, deer, or grasshopper.

A consumer that eats only other animals, such as a lion, hawk, or shark.

A consumer that eats both plants and animals, such as a bear, raccoon, or human.

A community of living organisms interacting with one another and with the nonliving (abiotic) parts of their environment, such as water, soil, and air.

The place where an organism lives that provides the food, water, shelter, and space it needs to survive.

The role or job an organism plays in its ecosystem, including what it eats, where it lives, and how it interacts with others.

All the members of a single species living in the same area at the same time.

All the different populations of organisms that live and interact in the same area.

An inherited trait or behavior that helps an organism survive and reproduce in its environment, such as a cactus's spines or a polar bear's thick fur.

An adaptation that lets an organism blend into its surroundings to avoid predators or sneak up on prey.

The seasonal movement of animals from one region to another to find food, breed, or escape harsh weather.

A state of greatly reduced activity and slowed metabolism that allows some animals to survive cold winters with little food.

The passing of traits from parents to offspring through genes carried on DNA.

A segment of DNA that carries the instructions for a specific trait, passed from parents to offspring.

Deoxyribonucleic acid, the molecule that stores genetic information and provides the instructions for an organism's traits.

A specific characteristic of an organism, such as eye color or seed shape, that can be inherited from its parents.

A characteristic passed from parents to offspring through genes, such as hair color, unlike a learned behavior.

A dominant trait masks a recessive one when both are present; a recessive trait appears only when no dominant gene is inherited.

The series of stages an organism passes through from birth to reproduction to death, such as a butterfly's egg, larva, pupa, and adult.

A dramatic change in body form during an animal's life cycle, such as a tadpole becoming a frog or a caterpillar becoming a butterfly.

The process by which a seed begins to grow into a new plant when it has enough water, warmth, and oxygen.

The transfer of pollen from one flower to another, often by insects, birds, or wind, allowing plants to reproduce.

The body system of bones and joints that supports the body, protects organs, allows movement, and produces blood cells.

The body system of muscles that works with the skeleton to produce movement and maintain posture.

The body system in which the heart pumps blood through vessels to carry oxygen, nutrients, and wastes throughout the body.

The body system, including the lungs, that brings oxygen into the body and removes carbon dioxide through breathing.

The body system that breaks down food into nutrients the body can absorb and removes solid waste.

The body system, including the brain, spinal cord, and nerves, that senses the environment and controls and coordinates body actions.

A large region defined by its climate and the plants and animals adapted to it, such as desert, tundra, rainforest, grassland, or taiga.

A cold, treeless biome with frozen subsoil (permafrost), low precipitation, and short growing seasons.

A dry biome with very little rainfall and large temperature swings, home to organisms adapted to conserve water.

A warm, wet biome with very high rainfall and the greatest variety of plant and animal life (biodiversity) on Earth.

A relationship in which one animal (the predator) hunts and eats another (the prey); this balance helps control population sizes.

A close, long-term relationship between two different species; types include mutualism, commensalism, and parasitism.

The variety of living things in an ecosystem; greater biodiversity generally makes an ecosystem more stable and resilient.

The permanent disappearance of a species when all of its members die out, often due to habitat loss or rapid environmental change.

The movement of materials such as carbon, nitrogen, and water through living things and the environment, recycling them for reuse.

The movement of carbon through the atmosphere, living things, oceans, and rocks via photosynthesis, respiration, decay, and combustion.

Sight, hearing, smell, taste, and touch — the ways organisms gather information about their environment.

A stimulus is a change in the environment that an organism reacts to; the reaction is the response, such as a plant growing toward light.

A living thing too small to see without a microscope, such as bacteria, many protists, and some fungi; some cause disease and some are helpful.

The principle that all living things are made of cells, cells are the basic unit of life, and all cells come from existing cells.

Levels of organization in living things: cells form tissues, tissues form organs, and organs work together as organ systems.

The process by which organisms make offspring; sexual reproduction combines two parents' genes, while asexual reproduction uses one parent.

The physical forms matter can take — solid, liquid, and gas (plus plasma) — determined by how its particles are arranged and how much they move.

A state of matter with a definite shape and volume because its tightly packed particles vibrate in fixed positions.

A state of matter with a definite volume but no definite shape; its particles are close together but can flow past one another.

A state of matter with no definite shape or volume; its particles move freely and spread to fill any container.

The change of a substance from a solid to a liquid when heat is added, such as ice becoming water at 0°C.

The change of a substance from a liquid to a solid when heat is removed, such as water becoming ice at 0°C.

The change of a substance directly from a solid to a gas without becoming a liquid, such as dry ice turning into carbon dioxide vapor.

A change in matter's form or appearance — such as cutting, melting, or dissolving — that produces no new substance and is often reversible.

A change that forms one or more new substances, such as burning, rusting, or baking; signs include gas, light, heat, or a color change.

The principle that matter is neither created nor destroyed in a physical or chemical change; the total mass stays the same.

The smallest unit of an element that keeps its chemical properties, made of protons, neutrons, and electrons.

A pure substance made of only one kind of atom that cannot be broken down by chemical means, such as oxygen, gold, or carbon.

Two or more atoms joined by chemical bonds, such as water $\ce{H2O}$ or oxygen gas $\ce{O2}$.

A substance made of two or more different elements chemically combined in fixed proportions, such as table salt $\ce{NaCl}$.

A positively charged particle in the nucleus of an atom; the number of protons (atomic number) defines the element.

A particle with no electric charge found in the nucleus of an atom, adding to its mass.

A negatively charged particle that moves around the nucleus of an atom; its arrangement controls how atoms bond.

The chart that organizes all known elements by increasing atomic number into rows (periods) and columns (groups) of similar properties.

A combination of two or more substances that are physically blended but not chemically bonded, so each keeps its own properties and can be separated.

A homogeneous mixture in which one substance (the solute) is evenly dissolved in another (the solvent), such as salt dissolved in water.

In a solution, the solute is the substance being dissolved (such as salt) and the solvent is the substance doing the dissolving (such as water).

A push or pull that can change an object's motion, direction, or shape; measured in newtons.

A change in an object's position over time relative to a reference point; described by speed, velocity, and acceleration.

How far an object travels in a given amount of time, calculated as $\text{speed} = \dfrac{\text{distance}}{\text{time}}$.

An object's speed in a specific direction; unlike speed, it includes which way the object is moving.

The rate at which an object's velocity changes over time, whether speeding up, slowing down, or changing direction.

The law of inertia: an object at rest stays at rest and an object in motion stays in motion at constant velocity unless acted on by an unbalanced force.

The acceleration of an object depends on the net force and its mass, expressed as $F = ma$.

For every action there is an equal and opposite reaction; forces between two objects are equal in size and opposite in direction.

The tendency of an object to resist a change in its motion; objects with more mass have more inertia.

The force of attraction between all objects with mass; on Earth it pulls objects toward the planet's center and gives them weight.

A force that opposes motion when two surfaces rub against each other; it can slow objects and produce heat.

Mass is the amount of matter in an object and stays constant; weight is the force of gravity on that mass and changes with location.

Balanced forces are equal and opposite and cause no change in motion; unbalanced forces cause an object to start, stop, or change motion.

A basic device that makes work easier by changing the size or direction of a force; the six types are lever, pulley, wheel and axle, inclined plane, wedge, and screw.

A simple machine consisting of a rigid bar that pivots on a fixed point (fulcrum) to lift or move a load, such as a seesaw or crowbar.

A simple machine made of a wheel and a rope used to lift loads by changing the direction or reducing the effort of a force.

A simple machine consisting of a flat, sloped surface that makes it easier to move a load to a higher place, such as a ramp.

A simple machine made of two inclined planes joined to form a sharp edge that splits or cuts objects, such as an axe or knife.

A simple machine made of an inclined plane wrapped around a cylinder, used to hold things together or lift material.

A simple machine of a larger wheel attached to a smaller rod (axle) that turn together, such as a doorknob or steering wheel.

The transfer of energy when a force moves an object a distance, calculated as $W = F \times d$; no work is done if the object does not move.

The ability to do work or cause change; it can be stored (potential) or in motion (kinetic) and changes from one form to another.

The energy of motion; a faster or heavier moving object has more kinetic energy.

Stored energy an object has because of its position or condition, such as a rock at the top of a hill or a stretched rubber band.

The principle that energy cannot be created or destroyed, only transformed from one form to another or transferred between objects.

The types energy can take, including mechanical, thermal (heat), chemical, electrical, light, sound, and nuclear energy.

The movement of energy from one object or place to another, such as the Sun's light energy warming the ground.

The transfer of thermal energy from a warmer object to a cooler one until both reach the same temperature.

A measure of the average kinetic energy of the particles in a substance; measured with a thermometer in degrees.

The transfer of heat through direct contact between particles, such as a metal spoon warming in hot soup.

The transfer of heat through the movement of a fluid (liquid or gas), such as warm air rising and cool air sinking.

The transfer of heat as electromagnetic waves that need no medium, such as the Sun warming Earth through the vacuum of space.

A conductor lets heat or electricity pass through it easily (such as metal); an insulator resists their flow (such as rubber or wood).

A form of electromagnetic energy that travels in waves, moves in straight lines, and lets us see; it travels faster than sound.

The bouncing of light (or sound) off a surface, which is how we see objects and how mirrors work.

The bending of light as it passes from one material into another, such as a straw appearing bent in a glass of water.

Opaque materials block light, translucent materials let some light through but scatter it, and transparent materials let light pass clearly.

The band of colors that make up white light — red, orange, yellow, green, blue, indigo, and violet — seen when light passes through a prism.

A form of energy produced by vibrations that travels as waves through a medium such as air, water, or solids; it cannot travel through a vacuum.

How high or low a sound is, determined by the frequency of the sound wave; faster vibrations produce a higher pitch.

How loud or soft a sound is, determined by the amplitude (height) of the sound wave; larger vibrations produce a louder sound.

A form of energy from the movement of electric charges (electrons); it can flow as a current through a conductor.

A complete, closed path through which electric current flows, typically including a power source, wires, and a device such as a bulb.

In a series circuit, current flows through one single path; in a parallel circuit, current splits among multiple paths so one break does not stop the others.

A force produced by magnets that attracts iron, nickel, and cobalt; like poles repel and opposite poles attract.

The amount of mass in a given volume, calculated as $\rho = \dfrac{m}{V}$; an object floats if it is less dense than the fluid around it.