LM 1b elements, compounds and mixtures Flashcards
what is an element?
a substance that contains only one type of atom. it cannot be split into anything simpler
what is a compound?
a substance made of two or more elements chemically combined
what is a mixture?
a mixture of two or more substances that are not chemically combined
what are the melting and boiling points of a pure substance?
they will have fixed melting and boiling points if they are pure, mixtures melt and boil over a range of temperatures
what does simple distillation do?
separates two liquids with different boiling points
what does fractional distillation do?
separates more than two liquids with different boiling points
what does filtration do?
separates an insoluble solid from a liquid
what does crystallisation do?
separates a soluble solid and a liquid
what does paper chromatography do?
separates more than one soluble solid
how do you separate a mixture of water and ethanol?
simple distillation
what is a molecule?
group of two or more atoms held together by chemical bonds
how does chromatography work?
the solvent moves up the marked paper and dissolves the ink.
what do we call the paper in chromatography?
stationary phase, doesn’t move
what is the solvent called in chromatography?
mobile phase, does move
what is an experiment so show the different colours in ink pens?
chromatography
draw a line on the paper chromatography and then put two ink dots, put the paper in a solvent and the colours should move up the paper with the solvent
- if there is only one colour on one of the sides then the colour is pure
- if there were two spots then you can tell the two different colours were a mix
how does paper chromatography work?
each chemical in the mixture will be attracted to the stationary phase to a different extent
- chemicals strongly attract will not move very far
- chemicals weakly attracted move further up
why do we draw the starting line in pencil in paper chromatography?
because pen ink would move up the paper with the solvent pencil doesn’t
how does filtration work?
a mixture is poured through filter paper in a funnel, the insoluble element will get trapped in the filter paper
how does crystallisation work?
leave the solution with soluble salt to evaporate, or gently heat
how does simple distillation work?
- evaporate liquid by heating
- then cool so the vapour is condensed
how does fractional distillation work?
- same thing as simple distillation but with a fractionating column
- liquids in mixture have to have different boiling points
- when vapours hit fractionating column it condenses
- when the boiling point of one of the chemicals is shown on the thermometer there is a relatively pure chemical getting cooled.
what is an unsaturated compound?
a compound that hasn’t reached its max amount of bonds
what is an unsaturated carbon bond?
a compound that has double carbon bonds
how do you test for unsaturated compounds?
bromine water - it turns colourless when added if double carbon bond is present
what is an isomer?
compounds with same molecular formula but different structures
