Science Vocabulary for 8th Grade
73 terms
JamWise Education Team·Updated March 2026
In 8th grade, students in the middle school (6-8) band encounter 73 essential science vocabulary terms. These words form the foundation for classroom discussions, reading comprehension, written assignments, and standardized assessments. Mastering this vocabulary gives students the language they need to express their understanding with clarity and confidence.
Below you will find every science term for 8th grade, organized by topic where applicable. Each term links to a detailed definition page with grade-level explanations, related vocabulary, and connections to JamWise learning resources.
earth-science
View topic hubCarbon cycle
The carbon cycle is the movement of carbon through Earth's atmosphere, oceans, soil, and living things.
Climate change
Climate change is a long-term shift in global temperatures and weather patterns, currently accelerated by human activities releasing greenhouse gases.
Geologic time scale
The geologic time scale is the system scientists use to organize Earth's 4.6-billion-year history into eons, eras, periods, and epochs.
Greenhouse effect
The greenhouse effect is the process where certain gases in Earth's atmosphere trap heat from the sun, keeping the planet warm.
Half-life
Half-life is the time it takes for half of the atoms in a radioactive substance to decay.
Nitrogen cycle
The nitrogen cycle is the process by which nitrogen moves through the atmosphere, soil, and living organisms.
Nonrenewable energy
Nonrenewable energy comes from finite sources that take millions of years to form, such as coal, petroleum, and natural gas.
Plate tectonics
Plate tectonics is the scientific theory explaining how Earth's lithosphere is divided into plates that move, causing earthquakes, volcanoes, and mountain building.
Renewable energy
Renewable energy comes from sources that are naturally replenished, such as solar, wind, hydroelectric, and geothermal power.
Sea-floor spreading
Sea-floor spreading is the process where new oceanic crust forms at mid-ocean ridges as magma rises and pushes plates apart.
Subduction
Subduction is the process where one tectonic plate slides beneath another, often forming deep ocean trenches and volcanic arcs.
Superposition
The law of superposition states that in undisturbed rock layers, the oldest layers are at the bottom and the youngest are at the top.
Tides
Tides are the regular rise and fall of ocean water levels caused mainly by the gravitational pull of the moon.
Troposphere
The troposphere is the lowest layer of Earth's atmosphere where all weather occurs and where we live.
Water table
The water table is the underground level below which the soil and rock are completely saturated with water.
engineering
View topic hubControl group
A control group is the group in an experiment that does not receive the treatment, used for comparison.
Dependent variable
The dependent variable is the factor that is measured in an experiment to see if it was affected by the independent variable.
Independent variable
The independent variable is the factor that the experimenter deliberately changes in an experiment to test its effect.
life-science
View topic hubAdaptation
An adaptation is an inherited trait that increases an organism's ability to survive and reproduce in its environment.
Biodiversity
Biodiversity is the variety of different species of organisms in an ecosystem or on Earth.
Carrying capacity
Carrying capacity is the maximum number of individuals of a species that an environment can support with its available resources.
Common ancestor
A common ancestor is an organism from which two or more different species evolved.
Evolution
Evolution is the gradual change in the characteristics of a population of organisms over many generations.
Fossil evidence
Fossil evidence is the preserved remains or traces of ancient organisms that scientists use to understand the history of life on Earth.
Genetic variation
Genetic variation refers to the differences in DNA among individuals of a species, which can lead to different traits.
Genotype
A genotype is the combination of alleles an organism has for a specific trait, written with letters like Bb or tt.
Limiting factor
A limiting factor is any resource or condition that restricts the growth of a population, such as food, water, or space.
Meiosis
Meiosis is the type of cell division that produces sex cells (eggs and sperm) with half the normal number of chromosomes.
Mutation
A mutation is a change in the DNA sequence of a gene that may create a new trait in an organism.
Natural selection
Natural selection is the process where organisms with traits better suited to their environment are more likely to survive and reproduce.
Phenotype
A phenotype is the observable physical characteristic of an organism, determined by its genotype and environment.
Punnett square
A Punnett square is a diagram used to predict the possible genotypes and phenotypes of offspring from a genetic cross.
Selective breeding
Selective breeding is when humans choose organisms with desired traits to reproduce, producing offspring with those traits.
Species
A species is a group of organisms that can interbreed and produce fertile offspring.
Symbiosis
Symbiosis is a close, long-term interaction between two species that live in direct contact.
Taxonomy
Taxonomy is the science of classifying organisms into groups based on shared characteristics.
physical-science
View topic hubAcceleration
Acceleration is the rate at which an object's velocity changes over time — speeding up, slowing down, or changing direction.
Atomic mass
Atomic mass is the total mass of protons and neutrons in an atom's nucleus, measured in atomic mass units.
Atomic number
The atomic number is the number of protons in the nucleus of an atom, which determines what element it is.
Chemical bond
A chemical bond is the force of attraction that holds atoms together in a molecule or compound.
Conduction
Conduction is the transfer of thermal energy through direct contact between particles of matter.
Convection
Convection is the transfer of thermal energy through the circular movement of heated fluids or gases.
Covalent bond
A covalent bond forms when two atoms share one or more pairs of electrons.
Density
Density is the mass of a substance per unit of volume, calculated as density = mass / volume.
Electric current
Electric current is the flow of electric charges (usually electrons) through a conductor.
Electromagnetic induction
Electromagnetic induction is the process of generating an electric current by moving a magnet through or near a coil of wire.
Electromagnetic spectrum
The electromagnetic spectrum is the complete range of electromagnetic radiation organized by wavelength and frequency.
Electromagnetic wave
An electromagnetic wave is a wave that can travel through empty space, carrying energy as vibrating electric and magnetic fields.
Electron
An electron is a tiny negatively charged particle that moves around the nucleus of an atom in energy levels.
Energy conservation
The law of conservation of energy states that energy cannot be created or destroyed, only transformed from one form to another.
Ion
An ion is an atom that has gained or lost electrons, giving it a positive or negative electrical charge.
Ionic bond
An ionic bond forms when one atom transfers electrons to another atom, creating oppositely charged ions that attract each other.
Isotope
An isotope is an atom of an element that has the same number of protons but a different number of neutrons.
Kinetic theory of matter
The kinetic theory of matter states that all matter is made of tiny particles that are always in motion.
Mechanical energy
Mechanical energy is the sum of an object's kinetic energy and potential energy.
Momentum
Momentum is the quantity of motion an object has, calculated by multiplying its mass times its velocity (p = mv).
Neutron
A neutron is a particle in the nucleus of an atom that has no electric charge.
Newton's first law
Newton's first law states that an object at rest stays at rest, and an object in motion stays in motion at the same speed and direction, unless acted upon by an unbalanced force.
Newton's second law
Newton's second law states that the acceleration of an object depends on the net force acting on it and its mass (F = ma).
Newton's third law
Newton's third law states that for every action force, there is an equal and opposite reaction force.
Ohm's law
Ohm's law states that voltage equals current times resistance (V = IR).
Parallel circuit
A parallel circuit has components connected on separate branches, so electricity can follow multiple paths.
Periodic table
The periodic table is a chart that organizes all known elements by their atomic number and chemical properties.
Power
Power is the rate at which work is done or energy is transferred, measured in watts.
Proton
A proton is a positively charged particle found in the nucleus of an atom.
Radiation
Radiation is the transfer of energy through electromagnetic waves that can travel through empty space.
Resistance
Resistance is a material's opposition to the flow of electric current, measured in ohms.
Series circuit
A series circuit has all components connected in one single loop, so electricity follows only one path.
Sublimation
Sublimation is when a solid changes directly into a gas without first becoming a liquid.
Thermal expansion
Thermal expansion is the tendency of matter to increase in volume when heated as its particles move faster and spread apart.
Voltage
Voltage is the electrical pressure that pushes electric charges through a circuit, measured in volts.
Wave properties
Wave properties include amplitude (height), wavelength (distance between peaks), frequency (waves per second), and speed.
Work
In science, work is done when a force moves an object over a distance, calculated as W = F x d.