8th Grade Science Final Exam Flashcards

A complete set of vocabulary flashcards covering matter, atomic structure, chemistry, thermodynamics, motion, forces, and energy based on the 8th grade science study guide.

Atoms

The basic building blocks of matter, composed of protons, neutrons, and electrons.

Element

A pure substance made of only one type of atom that cannot be broken down into simpler substances.

Molecules

Two or more atoms joined together.

Chemical Formula

A notation that shows the elements in a compound and the ratio of atoms present.

Solids

A state of matter where particles are packed closely together in a fixed and tight arrangement, vibrating in place.

Liquids

A state of matter with no definite shape but a definite volume, where particles are free to move.

Pressure of a Gas

The force exerted by a gas; it increases if the temperature of the gas increases while the volume is kept the same.

Nucleus

The center of an atom where protons and neutrons are located.

Valence Electrons

The electrons in an atom's outermost shell that are transferred or shared during the formation of chemical bonds.

Electron Cloud Model

The modern model of the atom describing a tiny, dense nucleus surrounded by a fuzzy cloud of moving electrons.

Dmitri Mendeleev

The scientist who organized the first periodic table in 1869 by arranging 63 elements in order of increasing atomic mass.

Atomic Number

One of the four pieces of information listed in each square of the periodic table, alongside element name, symbol, and atomic mass.

Metals

Elements characterized by shininess, malleability, ductility, and conductivity, making up about 75% of all known elements.

Mixture

A combination of two or more substances that are physically combined and retain their individual properties because they are not chemically bonded.

Mass

The amount of matter in an object, which stays the same anywhere in the universe.

Weight

The force of gravity pulling on a mass, which changes depending on the gravitational pull of the location.

Volume

The amount of space occupied by matter, measured in the International System of Units with the standard unit being the cubic meter.

Density

A property of a material determined by the formula: $\frac{\text{mass}}{\text{volume}}$.

Physical Change

Any change that alters the form or appearance of matter without producing a new substance.

Chemical Change

A change in matter that produces one or more new substances, such as when old chemical bonds are broken and new ones are formed.

Thermal Energy

The internal energy created by the random, vibrating movement of atoms and molecules within an object.

Chemical Energy

Potential energy stored in the chemical bonds that hold atoms and molecules together.

Nonmetals

Elements that are poor conductors of heat and electricity, are brittle solids or gases at room temperature, and are highly electronegative.

Ions

Atoms or groups of atoms that have gained or lost electrons, resulting in a net electrical charge.

Ionic Bonds

Bonds formed through the electrostatic attraction between oppositely charged ions, typically between metals and nonmetals.

Covalent Compounds

Compounds made of two nonmetals sharing electrons, named using numerical prefixes like di-, tri-, and tetra-.

Law of Conservation of Mass

The principle stating that in a closed system, mass cannot be created or destroyed, meaning total mass of reactants equals total mass of products.

Reference Point

An object or place used to determine if another object is in motion based on a change in position.

Speed

The rate at which an object covers distance, calculated by dividing the distance traveled by the time.

Velocity

A vector quantity that accounts for both the speed of an object and the specific direction of its movement.

Acceleration

The change in motion defined by the formula: $\frac{\text{Final speed} - \text{initial speed}}{\text{Time}}$.

Friction

The force that two surfaces exert on each other when they rub against each other, determined by how hard the surfaces push together and the types of surfaces.

Newton’s First Law of Motion

The law stating that an object at rest will remain at rest and an object moving at a constant velocity will continue at that velocity unless acted upon by an unbalanced force.

Newton’s Second Law of Motion

The law stating that acceleration depends on the object's mass and the net force acting on the object.

Newton’s Third Law of Motion

The law stating that if one object exerts a force on another, the second object exerts a force of equal strength in the opposite direction on the first.

Momentum

An object's property determined by multiplying its mass and velocity: $\text{mass} \times \text{velocity}$.

Law of Conservation of Momentum

The rule that the total momentum of interacting objects does not change in the absence of outside forces.

Work

The result of a force acting upon an object causing it to move in the direction of the force, calculated as: $\text{Force} \times \text{distance}$.

Power

The rate at which work is done or energy is transferred, calculated by dividing total work by time.

Efficiency

A calculation used to measure machine performance by dividing useful work output by total work input and multiplying by 100.

Simple Machines

The six basic types of machines: inclined plane, wedge, screw, lever, wheel and axle, and pulley.

Law of Conservation of Energy

The fundamental rule stating that energy cannot be created or destroyed.