chem exam
atom
smallest particle of an element
molecule
forms when two or more atoms bond together
element
a pure substance which can not be broken down by chemical means
compound
a pure substance that forms when two or more elements chemically combine
physical change
change that does not give you new products, formulas dont change, reversible
chemical change
produces different substances & dif properties, end up with something new, formulas change, irreversible
matter is broken down into what two categories
pure substances & mixtures
what are pure substances
elements & compounds, only one kind of particle & altered by chemical chanve
mixtures
solutions, suspensions & mechanical mixtures, more than one kind of particle & altered by phyiscal changs
homogenous
looks same thru out, elements compounds & solutions
heterogenous
looks dif thru out, suspensions & mech mixtures
solution
solvent mixed in a solution, form dissolve, seperate distill, alloy=mixture of metals
suspension
settles out, doesnt mix, solutions mix form ppt = suspensions, seperated bu filtered or centrifuge
mechanical mixture
doesnt mix, doesnt settle, picked apart or sieve
pure substance characteristics
fixed density m.p & b.p
mixture characteristics
not fixed density m.p or b.p
law of definite composition
principle stating that the proportion of elements in a specifc compound is a fixed quantity
chromatography
Rf= d1/d2
sample line - top of colour or solvent
divide colour bu solvent
d1= solute/colour distance
d2= solvent distance