8th GMAS Review

atoms

basic building block of matter; made of protons, neutrons, and electrons

molecules

smallest part of a compound (H2O); can be two or more of the same element BONDED together too (O2)

elements

pure substance that cannot be broken down; 117: 90 natural and 17 synthetic

nucleus

center of an atom; protons and neutrons

protons

positive subatomic particle; found in nucleus; atomic number

neutrons

neutral subatomic particle; found in nucleus

electrons

negative subatomic particles found outside of the nucleus in the electron cloud

atomic number

proton count; how the Periodic Table is arranged; number above the chemical symbol

atomic mass

protons plus neutrons; number below the chemical symbol

chemical symbol

letter or letters used for elements; example O is Oxygen or Na is Sodium

pure substances

elements and compounds (molecules)

compound

two or more elements BONDED together chemically; example H2O or NaCl

chemical formula

used to represent compounds or molecules; letters and numbers; example Fe3O2

subscript

small number to right of a chemical symbol that tells the number of atoms; CAN'T be changed

coefficient

number to left of chemical formula that tells how many molecules there are; CAN be changed

mixture

two or more substances combine without chemically bonding; example air or dirt

homogeneous mixture

looks the same all the way through; milk or salt water or alloy metals

heterogeneous mixture

looks different all the way through; pepper or dirt

states of matter

solids, liquids, gases, plasma

solid

definite shape and volume (size); locked together and vibrates

liquid

definite volume (size) but no definite shape; free to move and flow, more energy than solids

gas

no definite shape or volume; particles far apart and lots of energy

plasma

highly energized gas; rare on Earth but most abundant form in Universe; found in lightning and stars

vaporization

when liquid turns to gas; physical change

boiling point

temperature where liquid turns to gas; creates bubbles but NOT chemical change; physical change

water temperature changes

boiling is 212F or 100C

freezing is 32F or 0C

condensation

when gas turns to liquid; cold glass on a hot day; physical change

freezing

when a liquid turns to a solid; physical change

freezing point

temperature where a liquid turns solid; physical change

melting point

temperature when solid becomes a liquid; physical change

physical property

characteristic that can be observed or changed without making a new substance

density

relationship between mass and volume; formula is D=M/V; is a constant

weight

pull of gravity on an object; NOT mass; changes based on location

volume

how much space an object takes up; SIZE; V=LW

chemical properties

characteristic that describes how a substance will interact with others in a chemical reaction; will change the substance

reactivity

how easily an element will form bonds with other elements; chemical property

combustion

burning of a substance; requires oxygen; chemical property

physical changes

alters physical properties without changing the substance; can be reversed

chemical change

when a substance is changed into a new substance with different properties; chemical reaction involving chemical BONDS

periodic table of elements

chart that organizes elements in periods(rows) and groups(columns) by atomic number

periods

seven rows of the periodic table; each period has same number of electron shells; 7=7 or 1=1; elements NOT similar

groups

18 columns of periodic table; elements have similar chemical properties and same number of valence electrons

valence electrons

electrons in outermost shell; tells how atoms will combine and form compounds

elements on left of table

solids and metals

elements on right of table

gases, two liquids, and few solids (nonmetals)

last two groups on right

group 17 halogen gases and group 18 noble gases

transition metals

groups 3-12; in the middle

alkali metals

group one; form salts with group 17 halogens sodium and potassium burn in water

alkaline metals

group two; magnesium and calcium; very reactive

metalloids

in nonmetals between gases and solids; SEMICONDUCTORS; germanium and silicon

stairsteps

halogens

group 17, makes salts with group one alkali, reactive, called gases but bromine is liquid and iodine and astatine are solid

noble gases

group 18; non reactive or INERT under normal conditions

law of conservation of matter or mass

matter cannot be created or destroyed during a chemical reaction but can change form; reactants MUST equal products

reactants

substances before a reaction; on left of chemical reaction H2 + O --> H2O

products

substances after a reaction; on the right

Na + Cl ---> NaCl

energy

the ability to do work or cause change

work

the movement of an object through a distance; no movement = no work

mechanical energy

energy of a moving object; machines or parts of engine, hydroelectric power or wind; also potential plus kinetic energy

thermal energy

total amount of energy in all particles of an object; solids have less thermal than liquids and gases have more than both

heat

thermal energy transferred between to objects; always goes from high to low

chemical energy

energy stored between chemical BONDS in compounds and molecules; batteries, food, fossil fuels

electrical energy

energy from moving charges; gaining and losing ELECTRONS (electricity)

sound

energy given off from a vibrating object; has to travel thru matter in waves;

nuclear energy

energy from the NUCLEUS of an atom; fission or fusion

kinetic energy

energy from a moving object; depends on mass and velocity; KE= 1/2mass X velocity2

potential energy

stored energy due to position or composition; rock on hill or a battery or food (chemical)

PE=mass X height

law of conservation of energy

energy can change from one form to another but CANNOT be created or destroyed; potential becomes kinetic or chemical becomes electromagnetic

friction

force that opposes motion between two or more objects; steals energy; how breaks work

temperature

measure of average kinetic energy in an object; thermal is TOTAL kinetic energy

conduction

energy transferred through touch or direct contact; pan on stove, liquid warming ice

convection

energy transfer in liquids and gases through currents; wind currents, boiling water, cooking in oven

radiation

transfer of energy without matter with electromagnetic waves; vacuum or empty space; Sun warming Earth

force

push or pull

motion

change of position

speed

how fast an object moves; time and distance needed; Speed=distance/time S=D/T

velocity

speed of an object in a particular direction; changes if speed or direction changes

acceleration

is the rate an object's velocity changes; final velocity-start velocity/time

net force

total combination of all forces

balanced force

when the net force equals ZERO; no movement

unbalanced force

net force greater than zero; MOVEMENT

inertia

tendency to resist ANY change in motion; an object in motion keeps moving unless affected by an outside force (friction or gravity) or an object at rest stays at rest

gravity

force of attraction between all objects; affected by mass and distance; more mass=more gravity; closer distance=strong gravity

simple machine

device that makes work easier by changing size or direction of a force

inclined plane

straight, slanted surface like a ramp

wedge

inclined plane that is wider or thicker at one end; like a knife or axe

screw

inclined plane wrapped around a cylinder

lever

a bar that pivots on a fulcrum; 3 classes; shovel, wheelbarrow, hammer

pulley

rope or chain wrapped around a wheel; blinds

wheel and axle

two circular objects of different sizes, wheel is larger on the axle

wave

any disturbance that transfers energy thru matter or space

medium

material that waves can travel through

mechanical wave

wave that needs a medium to travel; like sound or water wave; CAN'T TRAVEL IN SPACE

transverse wave

wave that transfers energy perpendicular to its medium; think right angles

longitudinal wave

wave that travels back and forth

crest

top of transverse wave

trough

bottom of transverse wave