TASC Physical Sciences Level 3 key terms

A testable statement predicting how two or more variables are related, written so that observations can either support or contradict it during an investigation.

The factor that an investigator deliberately changes or selects in an experiment, so that its effect on the measured outcome can be observed.

The factor that is measured or observed in an experiment; its value is expected to respond to changes made in the independent variable.

An investigation in which all factors except the one being tested are held constant, allowing a fair comparison between treatment groups and a control group.

The comparison group in an experiment that does not receive the treatment being tested, providing a baseline for judging whether the treatment had an effect.

Accuracy describes how close a measurement is to the true value; precision describes how closely repeated measurements agree with one another, regardless of whether they are correct.

The digits in a reported measurement that carry meaningful information about its precision, including all certain digits plus one estimated digit.

The range within which the true value of a measured quantity is expected to lie, reflecting limits of the instrument and of the observer's technique.

A simplified representation of a real system, such as a diagram, equation, or physical object, used to explain observations and make predictions that can be tested.

A broad, well-supported explanation for a body of evidence that has survived repeated testing and is accepted by the scientific community until better evidence emerges.

The distance an object travels divided by the time taken, describing how fast position changes without regard to direction.

A vector quantity giving both the speed of an object and the direction of its motion; a change in either speed or direction changes velocity.

The rate at which velocity changes over time, including speeding up, slowing down, or changing direction; measured in meters per second squared.

A push or pull on an object that can change its motion or shape, measured in newtons and having both magnitude and direction.

The single combined effect of all forces acting on an object; when it is zero the object's motion does not change.

Three principles stating that objects resist changes in motion, that net force causes acceleration proportional to mass, and that every action has an equal and opposite reaction.

The tendency of an object to resist any change in its state of motion, determined by its mass; more massive objects are harder to accelerate or stop.

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

A force that opposes relative motion between surfaces in contact, converting some kinetic energy into thermal energy.

The energy an object possesses because of its motion, increasing with both mass and the square of its speed.

Stored energy that depends on an object's position or condition, such as height above the ground or the stretch of a compressed spring.

The principle that energy cannot be created or destroyed but only transferred or transformed between forms, so the total in a closed system stays constant.

Three ways heat moves: by direct contact between materials, by circulating currents in fluids, and by electromagnetic waves that need no medium.

The total internal energy of the particles in a substance, related to their random motion and to the substance's temperature, mass, and state.

The smallest unit of an element that retains the element's chemical properties, consisting of a nucleus of protons and neutrons surrounded by electrons.

A pure substance made of only one kind of atom, which cannot be broken into simpler substances by ordinary chemical means.

An arrangement of elements in order of increasing atomic number, organized so that elements with similar chemical properties fall into the same columns.

The number of protons in the nucleus of an atom, which identifies the element and determines its position in the periodic table.

One of two or more forms of the same element whose atoms have equal protons but different numbers of neutrons, giving different mass numbers.

The arrangement of an atom's electrons among energy levels and orbitals, which largely determines how the atom bonds and reacts.

An attractive force holding atoms together, formed by transferring or sharing electrons and classified as ionic, covalent, or metallic.

A substance formed when two or more different elements bond in fixed proportions, with properties unlike those of its constituent elements.

A combination of two or more substances that are not chemically bonded and can usually be separated by physical means, with variable proportions.

A homogeneous mixture in which a solute is dissolved in a solvent, with particles too small to settle out or be seen.

A scale from 0 to 14 describing how acidic or basic a solution is, based on the concentration of hydrogen ions.

A process in which substances are transformed into new substances with different properties by breaking and forming chemical bonds.

The principle that the total mass of the substances in a chemical reaction stays the same because atoms are rearranged, not created or destroyed.

The attractive force between any two objects with mass, which on Earth pulls objects toward its center and governs orbits.

The curved path an object follows around a more massive body, maintained by the balance between its forward motion and gravitational pull.

The Sun and all the objects bound to it by gravity, including planets, moons, asteroids, and comets moving in orbits.

The ongoing process by which rocks change among igneous, sedimentary, and metamorphic forms through melting, cooling, weathering, and heat and pressure.

The theory that Earth's rigid outer shell is broken into plates that move over the mantle, causing earthquakes, volcanoes, and mountain building.

Weathering breaks rock down in place through physical or chemical processes; erosion then transports the loosened material elsewhere by water, wind, or ice.