ACT Science Vocab

Independent Variable

the factor in an experiment that a researcher manipulates, changes, or selects to observe its effect on an outcome

Dependent Variable

the outcome factor or the element being measured in an experiment

Control Group

a baseline group of subjects that does not receive the experimental treatment

Hypothesis

a proposed explanation for a phenomenon that can be tested through scientific research and experimentation

Conclusion

the final judgment or interpretation based on experimental data

Prokaryote

a primitive, single-celled microorganism that lacks both a membrane-bound nucleus and specialized organelles

Eukaryote

organisms whose cells contain a distinct, membrane-bound nucleus and other specialized structures called organelles

Natural Selection

a core mechanism of evolution where organisms better adapted to their environment are more likely to survive and reproduce

Symbiosis

a close, long-term biological interaction between two different species

Atomic Number

the total number of protons found in the nucleus of an atom

Atomic Mass

the total quantity of matter in a single atom of an element, primarily comprising protons and neutrons

Valence Electrons

the electrons located in the outermost shell or energy level of an atom

pH scale

measures how acidic or basic a liquid is on a scale from (0) to (14). Pure water is neutral at (7.0), acids fall below (7.0) (down to (0), and bases (alkaline substances) measure above (7.0) (up to (14.0).

Chemical Bond

the fundamental attractive force that holds atoms or ions together to form molecules, crystals, and other compounds

Freezing Point

0°

Melting Point

100°

Solute

a substance that dissolves in a solvent to form a homogeneous mixture, known as a solution

Solvent

a substance that dissolves another substance, resulting in a uniform mixture

dilution

the process of reducing the concentration of a solute in a solution by adding more solvent

energy

the capacity to do work or cause change

Law of Inertia

an object at rest will stay at rest, and an object in motion will stay in motion at a constant speed and direction, unless acted upon by an outside force

Law of Force and Acceleration

the acceleration of an object depends directly on the net force acting upon it and inversely on its mass

Law of Action and Reaction

for every action, there is an equal and opposite reaction and this means that when one object exerts a force on a second object, the second object simultaneously exerts a force equal in strength and opposite in direction on the first

Potential Energy

the stored energy an object or system possesses due to its position, state, or configuration

Kinetic Energy

the energy an object possesses due to its motion

Earth’s Layers

divided into four main layers based on its chemical composition: the solid crust, the semi-fluid mantle, the liquid outer core, and the solid inner core

Rock Cycle

a continuous geological process where Earth's crustal materials—igneous, sedimentary, and metamorphic rocks—are continuously transformed from one type into another over time

Water Cycle

how water continuously moves on, above, and below Earth's surface

Solar System

our cosmic neighborhood, formed about 4.6 billion years ago from a collapsing cloud of gas and dust

Eclipse

occurs when one celestial body passes into the shadow of another or moves between it and a viewer