DC CAPE 2.0 Science Grade 8 flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Atom

The smallest unit of an element that still has that element's properties; it consists of protons and neutrons in a nucleus with electrons around it.

Conservation of Mass

In a closed system, the total mass of reactants equals the total mass of products because atoms are rearranged, not created or destroyed.

Balanced Chemical Equation

A chemical equation in which the number of atoms of each element is the same on the reactant and product sides, matching conservation of mass.

Physical vs Chemical Change

A physical change alters form or state without new substances; a chemical change produces new substances with different properties, such as rust forming.

Velocity

Speed in a stated direction. A change in velocity can be a change in speed, direction, or both, and it is called acceleration.

Newton's Second Law

The net force on an object equals its mass times its acceleration (F = ma). Doubling the force doubles acceleration; doubling mass halves it.

Inertia

The tendency of an object to resist changes in motion. Objects at rest stay at rest, and moving objects keep moving, unless a net force acts.

Balanced Forces

Forces that are equal in size and opposite in direction, giving a net force of zero, so the object's motion does not change.

Kinetic Energy

The energy of motion, calculated as one-half mass times speed squared (KE = ½mv²). Doubling speed quadruples kinetic energy.

Law of Conservation of Energy

Energy cannot be created or destroyed; it can only be transferred between objects or transformed from one form into another.

Conduction

Heat transfer by direct contact, in which faster-moving particles pass energy to slower particles in a cooler material, as when a metal spoon warms.

Energy Transformation

A change of energy from one form to another, such as chemical energy in food becoming kinetic energy when a person runs.

Wave

A disturbance that transfers energy from place to place without transferring matter; examples include sound, light, and water waves.

Frequency

The number of wave cycles that pass a point each second, measured in hertz; higher frequency means shorter wavelength at a fixed speed.

Wave Speed Equation

Wave speed equals frequency times wavelength (v = f × λ). If speed is constant, increasing frequency decreases wavelength.

Digital Signal

A signal encoded as discrete values such as 0s and 1s, which resists noise and can be stored and transmitted reliably compared with analog signals.

Photosynthesis

The process in which plants use light energy, carbon dioxide, and water to make glucose and release oxygen inside chloroplasts.

Cellular Respiration

The process in which cells break down glucose with oxygen to release energy, producing carbon dioxide and water as byproducts.

Cell Membrane

A thin boundary around a cell that controls which materials enter and leave, keeping the cell's internal conditions stable.

Levels of Organization

The arrangement of multicellular organisms from simplest to most complex: cells, tissues, organs, organ systems, and the whole organism.

Food Web

A model showing many interconnected food chains in an ecosystem, with arrows indicating the direction energy flows from eaten to eater.

Energy Pyramid

A diagram showing that only about 10% of energy passes from one trophic level to the next; most is lost as heat.

Carrying Capacity

The largest population an ecosystem can support over time given the available food, water, space, and other resources.

Mutualism

A relationship between two species in which both benefit, as when bees get nectar and flowers get pollinated.

Dominant Allele

An allele that is expressed in the phenotype whenever at least one copy is present, masking the effect of a recessive allele.

Genotype vs Phenotype

Genotype is an organism's genetic makeup, such as Bb; phenotype is the observable trait, such as brown eyes, resulting from genes and environment.

Punnett Square

A grid used to predict the possible genotypes and their probabilities in offspring by combining the alleles of two parents.

Mutation

A change in an organism's DNA that can alter a trait and is a source of new genetic variation in a population.

Seasons on Earth

Seasons are caused by Earth's tilted axis as it revolves around the Sun, changing the angle and amount of sunlight each hemisphere receives.

Moon Phases

The changing apparent shape of the Moon caused by the changing angle between Earth, the Moon, and the Sun, cycling about every 29.5 days.

Plate Boundaries

Divergent, convergent, and transform boundaries where tectonic plates move apart, collide, or slide past each other, causing earthquakes and volcanoes.

Rock Cycle

The ongoing process in which igneous, sedimentary, and metamorphic rocks change form through melting, cooling, weathering, erosion, and pressure.