Glossary
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Definitions were provided by Glencoe "Focus on Physical Science"
A
acceleration - rate of change of velocity with time
acid - a substance that contains a hydrogen atom and produces hydeonium ions when dissovled win water
Archhimede's principle - principle stating that the bouynt force exerted on an object by a fluid is equal to the weight of the fluid displaced by the object
asteroid - a rocky object, smller than a planet that is found between the orbits of Mars & Jupiter
astronomical unit - the average distance from Earth to the sun
atmospheric pressure - force exerted per unit area by air
atom - very small particle that makes up all matter
atomic number - the number of protons an atom has in its nucleus
B
balanced forces - forces that combine to forma net force of zero
base - a substance that can combine with hydrogen ions and produces hydroxide ions when dissolved in water
biomass - the total mass of all living things
black hole - a region of space from which no matter or radiation can escape (check out this animation that explains black holes)
boiling - vaporization that occurs within a liquid
buoyant force - the upward force exerted on an object by the surrounding fluid
C
chemical bond - a force that holdsatoms together in a compound
chemical change - a change of one or more substances into other substances
chemical property - the ability or inability of a substance to combine with or change into one or more new substances
comet - a small, icy body in orbit around the Sun, often having a highly elliptical orbit
compound - (1) a pure substance that contains two or more elements; (2) something that is formed by a union of elements
constant speed - an object travles the same speed each second
covalent bond - a chemical bond that forms when atoms share electrons
D
density - mass per unit of volume (d = m/v)
diatomic molecule - a particle consisting of two atoms
displacement - the difference between the inital position (starting point) and final position
ductility - the ability of a substance to be pulled into wires
E
eclipse - a total or partial obscuring of one celestial body by another
electron - a negatively charged particle that occupies the space in the atom outside the nucleus
electron cloud - the region surrounding an atomic nucleus where an electron is most likely to be found
element - pure substance made from atoms that all have the smae number of protons
F
force - a push or a pull
friction - a contact force that opposes the movement between to surfaces
G
galaxy - massive system of stars, dust, and gas held together by gravity
gas - a state of matter that has no fixed shape or volume
gravity - an attractive force between all objects that have mass
H
half-life - the time needed for one -half the mass of a smaple of a radioactive isotope to decay
hydrometer - an instrument that measures the density of a fluid
I
indicator - a compound that changes from one colr to another within a certain pH range
instananeous speed - speed at a specific instant in time
ion - an atom that is no longer neutral because it has gained or lost an electron
ionic bond - an electrical attraction between positively and negatively charged ions
isotope - one or more atoms of an element having the same number of protons in their nuclei, but a different number of neutrons
J
joule - the SI unit for energy
K
L
law of conservation of energy - energy is neither created or destroyed in a chemical reaction
law of conservation of mass - the total mass before a chemical reaction is equal to the total mass after a chemical reaction
light-year - the distance light travles in one year
liquid - a state of matter with a fixed volume but not a fixed shape
lunar phase - different appearance of the Moon as it orbits the Earth (Moon phase calendar)
M
malleability - the ability of a substance to be hammered or rolled into sheet
Mars - fourth planet from the sun
matter - anything that has mass and takes up space
mixture - a combination of two or more substances that can be sperated by physical means
molecule - neutral particle that forms as a result of electron sharing
N
nebula - a large cloud of gas and dust in space
net force - the combination of all forces acting on an object
neutron - a neutral particle located in the nucleus of an atom
Newton's first law of motion - An object at rest will remain at rest unless acted on by an unbalanced force. An object in motion continues in motion with the same speed and in the same direction unless acted upon by an unbalanced force.
Newton's second law of motion - The greater the mass, the greater the amount of force needed.
Newton's third law of motion - For every action there is an equal and opposite re-action.
noble gas - an element in Group 18 of the periodic table
nucleus - a region located at the center of an atom
O
organic compound - a large number of compounds that contain the element carbon
P
period - a horizontal row of elements on the periodic table
pH - a numerical scale used to indicate how acidic or basic a solution is
Q
qualitative data - describitions using words (observations)
quantitative - descriptions using numbers (more precise)
R
reactant - the starting material in a chemical reaction
red giant - a star with a radius much larger than the Sun's, it appears red because of its cool temperature
reference point - the starting point or origin used to describe an object's position
S
satellite - an object that orbits around a planet
scientific law - a rule that describes a pattern in nature
slope - the steepness of a line (rise over run)
solution - a homogenous mixture
speed - rate of change of position over time
T
tension force - a pulling force applied to an object
U
unbalanced forces - a net force that is not zero, causes movement
V
variable - a factor in a scientific investigation that can have more than one value
velocity - speed and direction (i.e. 30 km/hr. north)
W
weight - the measure of the gravitational pull on an object
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