Definitions Flashcards
mass number
total number of protons +neutrons in an atom
isotopes
atoms of the same element with same atomic number but different mass numbers
acid (Brønsted and Lowry)
a proton donor
base
a proton acceptor
alkali
a water-soluble base eg. CaO
strong acid
acid that ionises completely (100%)
weak acid
acid that ionises partially (
mole
a Si unit which measures the number of particles in a specific substance
Avogadro’s number
6.02*10^23
relative atomic mass
average mass of an atom of element based on its isotopic composition relative to carbon-12
relative molecular mass of compound
sum of the relative atomic masses of atomic species in formula
molar mass of molecule
mass of all the atoms in a molecule in g/mol
physical change
no new substance formed reversible changes of state - melting, evaporation, condensation, solidification breaking glass dissolving solids in water
chemical change
new substance formed not easily reversible energy change occurs burning Match cooking egg rusting
molecules
consists of two or more atoms combined together
compounds
consists of two or more elements combined together chemically with at least two different elements
mixtures
two or more different substances not chemically combined
metalloid
element with properties of both metals and non metals
heterogenous (insoluble)
sedimentation solid to liquid
recantation solid to liquid
filtration solid to liquid
separating funnel liquid to liquid
homogenous (soluble)
evaporation distillation crystallisation fractional distillation sublimation chromatography
from left to right reactivity: electro negativity: atomic radius: bonding/ionic:
high to low to high/low
increases
decreases
from bonding/ionic to covalent/ionic
down the periodic table
metallic activity increased
atomic radius increase
EN decreases
Polar Bonds
when a bonding pair of electrons is shared unequally and is not distrusted uni formally between the nuclei of two atoms, a polar bond is formed
when atoms have > 0.4 difference in EN and
polar molecules
molecules containing only non-polar bonds will be non-polar molecules
in a polar molecule one end of the molecule is slightly negative and one end is slightly positive
intermolecular forces
secondary bonding between molecules
determines some physical properties:
melting point
possible solvents
three types:
dispersion forces (vanderwaals force)
dipole-dipole
hydrogen bonding
dispersion forces
operate between ALL types of molecules
only force of attraction between non polar molecules
influenced by: number of atoms number of electrons polarity or non polarity of the molecule(shape) size of the molecule
very weak
ELECTRONS ARE ALWAYS MOVING IN A COVALENT BOND AND ARE MOVING ABOUT BOTH ATOMS THUS TEMPORARY DIPOLES ARE FORMED
DUE TO TEMPORARY DIPOLE FORMED IN ONE MOLECULE, THE ELECTRONS OF NEARBY MOLECULES WILL ADJUST TO FORM TEMPORARY DIPLES (INDUCED DIPOLES)
dipole dipole forces
only between polar molecules
polar bonds are present
permanent dipoles
higher mp and bo than similar non polar molecules
hydrogen bonding
special case of dipole dipole reactions
much stronger than dipole dipole
molecule will have a H atom covalently bonded to a very electronegative atom
H - N
H - O
H - F
very large fractional charges
very strong attraction between the molecules
THE LARGE POSITIVE FRACTIONAL CHARGE ON A H ATOM COVALENTLY BONDED TO A VERY LARGE EN F ATOM IS ATTRACTED TO TJE NEGATIVE FRACTIONAL CHARGE ON A F ATOM ON A NEIGHBOURING MOLECULE
solute
the minor component in the solution, is being dissolved
solvent
the liquid in which a solute is dissolved in
strong and weak bases
strength of base is determined by production of OH ions
strong bases dissociate completely
NaOH +aq = Na+ +OH-
weak bases dissociate partially
NH3 + h2o >
physical properties of bases
bitter soapy generally colourless can conduct electricity reacts with indicators to give characteristic colours
turns yellow in methyl orange
pink in phenolphthalein
blue in bromythol blue
metallic oxides
generally basic oxides
if water soluble, form alkaline solution
non metallic oxides
acidic oxides
Properties of acids
be in form solid liquid or gas sour taste do not conduct electricity in pure form need to add water for electrical conductivity (ions must be formed) Covalent bonding and molecular structure means low melting and low boiling pints detected with indicators methyl orange - pink
aim of titration a
The purpose of a titration experiment is to discover the concentration of an unknown acid or base, by neutralizing it with a measured quantity of a base or acid solution whose concentration is known.
In titrations, the known solution is the titrant and the unknown solution is the analyte.
