C1 Flashcards
what are the 3 separation techniques
filtration, crystallisation, distillation
what is filtration used for
to separate substances that are insoluble in a solvent from those that are soluble in the solvent
that is crystallisation used for
to obtain pure salt from a salt solution following filtration
what is distillation used for
to evaporate the solvent by heating and boiling a solution. the vapour enters a condenser where it is cooled and condensed into a liquid leaving the dissolved solids in the heated flask
what is a mixture
2 or more substances not chemically combined
what is chromatography process
when you dab a spot of the solution on a pencil like near the bottom of a sheet of chromatography paper. put the paper in a beaker of solvent and the more soluble the substance in the solvent the further up the paper the ink is carried
what is atomic number
number of protons and electrons in an atom of that element
what order is the periodic table in
order of atomic number
what is mass number
number of protons + neutrons in an element
what is an isotope
an atom of the same element but with different number of neutrons
what can differ between isotopes
physical properties can differ but chemical properties are always the same
what does the group number of an element tell you
the number of electrons in the outer shell as it’s the same as the group number
what did john dalton do
arranged the elements in order of atomic weights in 1808
what did john newlands do
in 1864 arranged the known elements in order of mass and realised that properties of every 8th element seemed similar
what did dmitri mendeleev do
1869- founded basis of modern periodic table but left gaps for undiscovered elements
why do elements in the same group react in similar ways
because their atoms have the same number of electrons in the outer shell
what are typical properties of metals
high melting and boiling points, ductile, malleable (lose electrons)
what are typical properties of non metals?
electrical insulators, brittle (gain electrons)
which group are the alkali metals
group 1
what is an alloy
a mixture of 2 or more elements (at least 1 being a metal)
why are metals malleable
the delocalised electrons allow the lattice to distort. when struck by a hammer the metal atoms can slip past one another without breaking up
what are metals ductile
the layers of metal atoms slide over each other easily without the metal breaking
as the atoms go down a group they get larger and lose electrons more easily and gain electrons less easily, why?
because the outer electrons are further away from the attractive force of the nucleus because there are more shells
what can the period number tell you about an element
the number of shells in its atom
