chem week 1 Flashcards
scientific theory
concise, extensively tested explanation of widely observed natural phenomena
scientific law
concise + generally applicable statement of a fundamental scientific principle (math, how)
atoms
smallest particle of an element, cannot be chemically or mechanically divided into smaller pieces
element
a pure substance that cannot be separated into simpler substances
compound
pure substance, 2 or more elements chemically bonded in fixed proportion
law of constant composition
compound always has the same elemental composition by mass, no matter its source ie: PURE WATER
law of multiple proportions
when 2 masses of one element react with a given mass of another to form two compounds, the two masses of the first element have a ratio of two small whole numbers ex: 15g O campared to 10g O has a ratio 3:2
chemical formulas
notation that uses the symbols of the elements to represent the elemental composition of a pure substance ie) SO2 SO3
matter
anything with mass, occupies space
pure substance
matter with constant composition, cannot be broken down into simpler matter by any PHYSICAL process
physical process or change
transformation of a sample of matter such as physical state change that does not alter chemical identity of any substance in sample
ie) state change
intensive properties
property that is independent of the amount of substance ie)density
extensive property
varies with amount of substance ie) mass
physical property
observed with out changing substance into another ie)density (state changes)
density
ratio of mass of an object to its volume d=m/v
chemical property
observed only by reacting substance with smt else (identity changes)
chemical bond
force holds two atoms/ions in a molecule/compound
molecule
collection of chemically bonded atoms, usually neutral
ion
particle consisting of one or more atoms, has net pos/neg charge
mixtures
two or more pure substances, homogenous or heterogenous
homogenous mixture
components distributed uniformly, composition and appearance uniform, appears even
heterogenous mixture
not distributed uniformly, contains regions of different composition
distillation
process using evaporation. or condensation to separate mixtures with different volatilities (water, gas)
filtration
process separating solid particles from liquid or gas (coffee, dust)
chromatography
process separating a mixture of substances according to different affinities (forensics)
energy
capacity to do work
work
exertion of a force through a distance w = f x d
potential energy
energy stored in object because of its position or composition