8th Grade Science - Semester Exam Study Vocabulary

Term Definition
symbiosis a relationship in which two organisms live in close association with others
commensalism a relationship in which one organism benefits and the other is neither harmed or helped
parasitism a relationship in which one organism benefits and the other is harmed
mutualism a relationship in which both organisms benefit
predator an animal that lives by capturing prey as a means of maintaining life
prey an animal taken by a predator as food
food web a network of interconnected food chains in an ecosystem
energy pyramid a diagram that shows the trophic levels of organisms in a food web
producer an organism that is capable of performing photosynthesis to use the Sun's energy directly
consumer an organism that must consume other organisms for nutrients
autotroph an organism that can make its own food
heterotroph an organism that must obtain its energy from an outside source
decomposer organisms such as bacteria and fungi that break down the remains of dead plants and animals
biotic factors living things in the environment, such as plants and animals
forces a push or pull
abiotic factors non-living things in the environment, including soil, water, temperature, light, wind, and minerals
parts of the atom proton, neutron, electron, nucleus, electron shell
proton positively charge particles that arene located in the nucleus of an atom
neutron a subatomic particle that has no charge and is located in the nucleus of an atom
electron a subatomic particle that has a negative charge
atomic mass the total number of protons and neutrons in an atom's nucleus
AMU unit of measurement of atomic particles; atomic mass unit = used to indicate mass on an atomic or molecular scale
Bohr Models electrons move in definite orbits around the nucleus (much like the planets around the sun) according to this model.
family / group a vertical column of elements in the periodic table; elements in a group share chemical properties
period In chemistry, a horizontal row of elements in the periodic table
valence electrons an electron that is found on the outermost shell of an atom and that determines the atoms chemical properties
metal an element that is shiny and conducts heat and electricity easily
non metal an element that is a poor conductor of heat and electricity
metalloid an element that has properties of both metals and nonmetals; sometimes referred to as a semiconductor
noble gases elements in family 8A
Law of Conservation of Mass the mass of reactants must equal the mass of all products, mass is neither created nor destroyed (balanced chemical equation)
States of Matter solids (fixed shape and volume), liquids (fixed volume and shaped by the container), and gases (filing the container)
Balanced Equations a symbolic representation of a chemical reaction in which both sides of the equation contain equivalent numbers of atoms of each element. The mass and the charge must be balanced on both sides of the reaction.
molecule a team of atoms; can be the same type of atom
subscript a number written below and to the right of a chemical symbol; shows the number of a specific type of atom present
coefficient a number placed in front of a chemical symbol or formula during balancing of the equation
evidence of a chemical color change; temperature change
reaction resistance or opposition to a force, influence, or movement
chemical change a change in matter that produces one or more new substances (chemical reaction)
physical change any change that alters the form or appearance of a substance but does not change the substance into another substance (i.e., crushing a can, melting ice cube, and breaking a bottle)
potential energy stored energy (example: a rubber band stretched before it is released)
kinetic energy energy of motion (example: rubber band being shot)
Newton's 1st Law The law of inertia:
Objects at rest, stay at rest. Objects in motion, stay in motion until an outside force is applied.
Newton's 2nd Law force is determined by the mass and acceleration of an object
Force = Mass x Acceleration
Newton's 3rd Law for every action, there is an equal and opposite reaction
inertia the tendency of a physical object to remain still or continue moving, unless force is applied
velocity speed in a certain direction
speed distance traveled in time
acceleration change in velocity
displacement space of one mass by another
balanced forces two or more forces whose effects cancel each other out and do not change the motion of an object
unbalanced 2 or more forces acting on an object that do not cancel and cause the object to accelerate
work force exerted on an object that causes it to move
motion graph graph showing a change in position measured by distance and time.
speed graph graph showing steeper line the faster the object travels (by distance and time).
position graph graph showing the position of an object (by distance and time). For example, a horizontal line means the object is not changing its position. A downward sloping line means the object is returning to the start.

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