Studied by 13 people
atoms
smallest particles of matter, that we cannot break down further by chemical means
parts of an atom
a nucleus and a cloud of electrons that move around the nucleus
nucleus
cluster of two kinds of particles, protons and neutrons
mass of an atomās particles
protons - 1 unit
neutrons - 1 unit
electrons - almost nothing
charge of an atomās particles
protons - positive charge (1+)
neutrons - none (neutral)
electrons - negative charge (1-)
protons
allow an atom to be identified
number of protons and electrons
every atom has an equal number of protons and electrons (no overall charge)
nucleon number
total number of protons and neutrons
elements
an element contain only one kind of atom
compounds
atoms of different elements chemically bonded together in a fixed ratio
described by a formula, made from symbols of the atoms on it
mixtures
contain more than one element or compound in no fixed ratio, which are not chemically bonded and can be separated by physical methods
can be separated by physical means
physical change
change if no new chemical substance is formed
homogenous mixture
mixture with uniform composition throughout
heterogenous mixture
mixture that has a non-uniform composition throughout
signs of a chemical change
one or more new chemical substances are formed
energy is taken in or given out during the reaction
change is usually difficult to reverse
filtering
separating a solid from a liquid
trapped solid (residue)
water (filtrate)
recrystallisation
method of purifying a compound by removing any impurities that might be mixed with it
evaporation
evaporating all the solvent
simple distillation
involves heating the liquid mixture to its boiling point, allowing the lower boiling component to vaporize and then condensing the vapor back into a liquid state
fractional distillation
technique for separating mixtures with close boiling points by repeatedly vaporizing and condensing them within a specialized column, achieving a much purer separation than simple distillation.
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