Download 2015 8th grade Science Study Guide Extended Version

CHEMISTRY:
Element—pure substance that cannot be changed into simpler substances; found on the periodic table
Atom—smallest particle of an element
Electron—negatively charged atomic particle that orbits the nucleus in the electron cloud
Proton—positively charged particle found in the nucleus of an atom
Neutron—neutral (no charge) particle found in the nucleus of an atom
Compound—pure substance made of two or more types of elements that are chemically combined
Molecule—smallest particle of a compound
Mixture—combination of two or more substances that retain their own physical properties and can be
separated; not chemically combined
Heterogeneous Mixture—mixture in which the substances are visibly distinguished (example: trail mix)
Homogeneous Mixture—substances are evenly mixed and cannot be visibly distinguished (example: sat
water)
Solid—state of matter in which the particles are locked in position and can only vibrate
Liquid—state of matter in which the particles slide past each other taking the shape of the container
Gas—state of matter in which the particles move freely, colliding frequently; has no definite shape
Valence—outer level electrons in an atom; involved in bonding
Physical Properties—can be observed or measured without changing the matter studied
Density—property that describes the relationship between the mass of a material and its volume
(D=M/V)
Solubility—ability to dissolve in a substance
Malleability—property of metals that allow them to be hammered into flat sheets
Ductility—property of metals that allow them to be drawn into a wire
Physical Change—change in one or more physical properties (example: change in size or state)
Chemical Change—results in the formation of one or more new substances with new chemical and physical
properties. Signs: unexpected color change, energy given off as light or heat, formation of a
precipitate (solid), or formation of a gas
pH—measure of how acidic or basic a substance is; scale from 1-14
Acid—substance with a pH less than 7
Base—substance with a pH more than 7
RESOURCES:
Nonrenewable—resources that cannot be replaced in nature (example: fossil fuels)
Renewable—resources that can be replaced or reused in nature (example: solar power)
Conservation—preventing the loss of a resource by way of thoughtful management of it
WATER:
Aquifer—large deposit of groundwater that can be extracted and used (must dig a well)
River Basin (watershed)—portion of land drained by a river and its tributaries
Tributary—smaller river or stream that feeds into a larger river
Permeability—measure of the ability of rock or sediment to allow water through it
Estuary—areas where fresh and salt water mix; nurseries for fish and filter pollutants out of water
Upwelling—cold water along the ocean bottom rises carrying nutrients to the surface; caused when warm
surface water near coastal areas is blown offshore by winds
Phytoplankton—microscopic plants that float at the water’s surface
Zooplankton—microscopic animals found in water; often eat phytoplankton
Turbidity—measure of how clean water is (muddiness)
Hydrosphere—all the water on Earth (fresh and salt)
Bioindicators—living organisms (macroinvertebrates) used to determine the health of a body of water
Non-point Source—pollution that comes from many unidentified sources and reaches a body of water
through runoff
Point Source—pollution that enters water directly from a specific source (example: a pipe dumping waste
into a river)
Salinity—measure of the amount of salt in water
Polarity—property of water in which each end of the molecule has a slight charge; makes water an
excellent solvent (“universal solvent”)
Cohesion—force that holds molecules of water together; allows water to form drops
Adhesion—attractive force between water and other substances it comes in contact with
Specific Heat—amount of energy needed to raise 1 kg of a substance by 1 oC; water has a high specific
heat
GEOLOGIC TIME:
Fossil—preserved remains or traces of an organism that lived in the past
Mold—fossil formed when sediments bury an organism and the organism decays leaving a cavity in the
shape of the organism
Cast—fossil formed when a mold is filled with sand or mud that hardens into the shape of the organism
Preserved Fossil—forms when the entire organism or parts of organisms are prevented from decaying by
being trapped in rock, ice, tar, or amber (tree sap)
Trace Fossil—forms when the mud or sand hardens to stone where a footprint, trail, or burrow of an
organism was left behind; tells about animal’s behavior
Petrified Fossil – formed when minerals soak into buried remains, replacing the remains and changing
them into rock
Geologic Time Scale—record of the major events and diversity of life forms present in Earth’s history
Relative Dating—tells the age of one object compared to the age of another object; does not tell the
exact age in years
Law of Superposition—for undisturbed layers of rock, the oldest layer is at the bottom and the layers
become younger as you go up
Index Fossil—Fossil used to date rock layers
Radiometric Dating—uses the amount of radioactive materials in rock to determine the exact age of an
object (absolute dating)
Radiocarbon Dating—uses Carbon-14 to determine the age of material that was once living
Fault—break in the rocks that make up the Earth’s crust that is formed due to the movement of rock on
either side
MICROBIOLOGY AND DISEASE:
Virus—non-living particles that invade healthy cells forcing them to make more viruses
Bacteria—single-celled organisms without a nucleus
Vaccine—used to prevent viral diseases
Antibiotics—medicines used to treat bacterial infections
Parasite—organism that feeds on another individual (host) causing harm to that individual
Epidemic—spread of an infectious disease among a population
Pandemic—world-wide epidemic
Biotechnology—the use of living organisms to solve problems and make useful products
ECOLOGY:
Ecosystem—interactive systems that include both biological (biotic) and physical (abiotic) components of
the environment
Population—group of organisms belonging to the same species that live in a particular area
Predation—interaction between species in which one species (predator) eats the other (prey)
Competition—relationship that occurs when two or more organisms need the same resource at the same
time
Symbiosis—relationship that exists between organisms of two different species that live together in
direct contact
Mutualism—symbiotic relationship in which both organisms benefit
Biosphere—all the living things on the Earth
Food Chain—simplest path that energy takes through an ecosystem
Food Web—interconnected food chains
Producer (autotroph)—organism that makes its own food through photosynthesis or chemosynthesis
Photosynthesis—process of using sunlight to make food in the form of sugar (glucose)
Chemosynthesis—process of using chemicals like methane or sulfur to make food; used by bacteria at
deep sea thermal vents
EVOLUTION:
Evolution—change in species over time
Natural Selection—organisms best suited for their environment survive and pass on their beneficial
genetic mutations to their offspring; “survival of the fittest”
Plate Tectonics—movement of Earth’s continental and oceanic plates continually change the shape of
Earth’s crust
Continental Drift—theory that Earth’s continents were once together (Pangaea), broke apart, and
drifted to their current locations
Subduction—forcing of one plate beneath another
MOLECULAR BIOLOGY:
Basal Metabolic Rate (BMR)—amount of energy required to maintain essential life functions
Metabolism—set of chemical reactions used in strong food and converting it into energy (ATP)
Calorie—measure of the amount of energy in food