Elements, compounds and mixtures (checklist)
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all substances are classified into one of three types :
compounds mixtures elements
what is an element
A substance made of only one type of atom cannot be split into anything simpler
what is a compound
A pure substance made up of two or more elements chemically combined
what is a mixture
A combination of two or more substances (elements and/or compounds) that are not chemically combined
can mixtures be separated by physical methods
yes
can compounds be separated by physical methods
no
example of element
gold, silver, sodium
example of a compound
carbon dioxide, sodium chloride
example of a mixture
the atmosphere
if you have a pure substance, when the melting/boiling point is reached, what happens
the entire substance will melt or boil at the same time
a pure substance has a ___ melting/boiling point
fixed
when you melt a mixture,
each part gets melted separately
a mixture does/doesn’t have a fixed melting / boiling point
doesn’t
mixtures melt and boil over a ____ of temperatures
range
simple distillation separates
two liquids with different boiling points
fractional distillation separates
more than two liquids with different boiling points
filtration separates
an insoluble solid and a liquid
crystallisation separates
a soluble solid and a liquid
paper chromatography separates
more than one soluble solid
how is simple distillation done
• solution is heated ( in between the boiling points of both liquids, so that only one evaporates) • the vapour will travel through a tube which has a condenser around it, which will be pouring cold water win, and cold water out. This causes the vapour to cool so condense back into a liquid when it gets back to the other side of the tube, it is back into liquid form and has been separated
how is fractional distillation done
the same as simple distillation, just that because there are more than 2 liquids, you need to switch the beaker after you have separated the first one from the others.
how is filtration done
get a funnel with filter paper pour the mixture into that the liquid will fall through and into the beaker the insoluble solid will remain stuck because of the filter paper and so you will have separated them
how is crystallisation done
• you need a bunsen burner, a tripod, a beaker dull of water and a cruscible on an evaporating dish put the solution in the cruscible and heat it until it reduces by about half the amount leave it to dry naturally the crystals of the dissolved solid will form as the solvent evaporates
how is paper chromatography done
• a pencil line is drawn of the paper and spots of the sample are drawn on it • paper is lowered into solvent container and the pencil line must be right above the level of solvent so the samples don’r wash into the solvent container • the solvent will then travel up the paper, taking some of the coloured susbtance with it • Different substances have different solubilities so will travel at different rates This causes the substances to separate Those substances with higher solubility will travel further than the others This will show the different components of the ink / dye