Helpful Science Terms to Know for the ACT Science Test

By Lisa Zimmer Hatch, Scott A. Hatch

The answers to ACT Science Test questions come mostly from information in the passages, but every once in a while, you’ll encounter a question that requires you to conjure up a scientific term or rule you learned in middle school.

Refresh your memory with this short glossary of science basics.

Scientific Term Definition
Acceleration The rate of change in velocity
Allele A gene variant
Atom A particle that contains protons, neutrons, and electrons and
is the smallest part that can be involve in a chemical
reaction
Boiling point The temperature when a liquid becomes a gas
Buoyancy The ability of an object to float
Cell The smallest independent element of an organism
Charge The either positive or negative amount of unbalanced
energy
Chemical reaction The rearrangement of atoms to form new substances
Chromosomes The structure of nucleic acids and proteins that carries the
genetic material in a cell
Compound A substance made up of more than one element
Conduction Heat transfer as a result of molecular interaction
Constant The elements of an experiment that are controlled to remain the
same
Control group The group in an experiment that provides a standard for
comparison because it doesn’t receive the independent variable
Convection Heat transfer as a result of fluid movement
Density The mass per volume in a substance
Dependent variable The variable in an experiment that changes as a result of
effect of the independent variable
Elasticity The ability of a substance to return to its original shape
Electrons Negatively charged atomic particles
Element A substance comprised of atoms with the same atomic number and
cannot be split into smaller substances
Fluid A liquid or gas
Gamete A sex cell that carries the genes of both parents
Gene A section of DNA that determines inheritance
Gravity The force that attracts an object toward the center of the
earth
Hypothesis The prediction of how the independent variable in an experiment
will affect the dependent variable
Independent variable The variable controlled by the experimenter
Inertia The tendency of a body to remain at rest
Ion Atom with an unbalanced electrical charge due to a loss or gain
of electrons
Kinetic energy The energy of a body in motion
Mass The quantity of a body’s matter
Molecule A group of bonded atoms
Neutrons Particles with zero charge
Nucleus The part of the atom that contains protons and neutrons
Potential energy The amount of useable energy a body has when it’s not
moving
Protons Particles with a positive energy charge
Radiation Transfer of energy as waves or rays
Reactants The substances that participate in a chemical reaction
Variables The elements of an experiment that change or could change
Velocity The rate of change in distance with respect to time