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
kinetic energy
energy of object in motion because of mass and speed
KE = 1/2 mu^2
heat
transfer of energy between objects that occur because of differences in temp
law of conservation of energy
cannot be created nor destroyed, but can change forms
molecular formula
chem formula that indicated how many atoms of each element are in one mol of pure substance C6H12O6
structural formula
representation of molecule that uses short lines between symbols of elements to show chem bonds between atoms CH3-C-CH3
ionic compounds
consists of a characteristic ratio of pos ions and neg ions ie) NaCl
empirical formula
chem formula in which subscripts represent the simplest whole number ratio of the atoms/ions in compound
*ionic compounds always empirical
SI units
set of base and derived units used worldwide to express distances and quantities of matter and energy
T(K)=
T(C) + 273.15
T(C)=
(5/9) (T(F) -32)
precision
the extent to which repeated measurements of the same variable agree (HOW REPEATABLE)
accuracy
how close to true value (HOW CORRECT)
if this much sulfur added to this much oxygen to make SO2, then this much sulfur and HOW MUCH OXYGEN to make SO3??
- find moles of known
- stoichiometry to find moles of unknown
- MM to find g of unknown
melting
solid –> liquid
deposition
gas –> solid
sublimation
solid –> gas
vaporization
liquid –> gas
condensation
gas –> liquid
freezing
liquid –> solid
lifting BRICK
increases pot energy, pos!
ICE CUBE in hand
thermal energy goes into system, pos!
AIR BALLOON
not enough info: temp, pressure, etc
kilo
10^3
centi
10^-2
nano
10^-9
milli
10^-3
micro
10^-6
pico
10^-12
low of multiple proportions example
15g O + 10g S
10g O + 10g S
15/10 = 3/2
can distillation remove soil particles from water? (solid from liquid)
Yes, but it would require much more energy
properties used to distinguish things
- physical
- chemical
- density
- conductivity
- element/compound/mixture
between particles of gas?
empty space
what kind of property? density
physical
what kind of property? reacts with oxygen
chemical
what kind of property? boiling point
physical
what kind of property? conductivity
physical
mean
average calculated by summing all values in a series and dividing sum by number of values
standard deviation
a measure of the amount of variation in a set of related values
confidence interval
range of values that has a specified probability of containing the true value of a measurement
solid
definite volume and shape
liquid
definite volume but not shape
gas
neither definite volume nor shape
