chemical analysis
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pure substances and formulations -a pure substance can be a single element -a pure substance can also be a single compound -a pure substance is not mixed with any other substance what is true about a pure susbatnce’s melting and boiling point (Pick 2) A) a pure substance melts over a range of temperatures B) a pure substance boils at a specific fixed temperature C) a pure substance melts at a specific fixed temperature D) a pure substance boils over a range of temperatures
B) a pure substance has a specific fixed boiling point C) a pure substance melts at a specific fixed fixed temperature
impure substances melt and boil over a range of temperatures if a sample of water boils over a range of temperatures is it pure or impure?
is the sample boils over a range of temperatures than it is an impure substance because impure substances boil over a range of temperatures
what are formulations
formulations are a complex mixture that has been designed as a useful product in a formulation quantity of each component is carefully measured so that the product has the properties we need.
examples of formulations
• fuels • cleaning products • alloys • fertilisers • medicine • paint
All separation techniques including paper chromatogrpahy are physical processes why
because they do not involve chemical reactions, no new substances are made
what is paper chromatography
paper chromatography allows us to separate substances based on their different solubilities
how do we carry out paper chromatography
we take a piece of chromatography paper and draw a pencil line at the bottom. we put a dot of our first colour on the pencil line now we put a dot of our second colour we must do this for several colours as long as there is enough space on the paper. now place bottom of paper into a solvent solvent makes its way up the paper and dissolves the ink. these are carried up the paper as well
how do we carry out paper chromatography
we take a piece of chromatography paper and draw a pencil line at the bottom. we put a dot of our first colour on the pencil line now we put a dot of our second colour we must do this for several colours as long as there is enough space on the paper. now place bottom of paper into a solvent solvent makes its way up the paper and dissolves the ink. these are carried up the paper as well
what is the definition of a solvent
liquid that will dissolve substances
what is the stationary phase and what is the mobile phase
stationary phase- paper ( does not move) mobile phase- solvent ( moves up the paper)
pure substances will produce a single spot because…
pure substances will produce a single spot because they are not mixed with any other substance.
in context: if one of the colours has separated into two different spots what does it mean
it is a mixture of two different substances
why does paper chromatography work
because each chemical in the mixture is attracted to the stationary phase to a different extent.
chemicals that are strongly attracted to the stationary phase will: A) move further up the paper B) not move very far
A) chemicals that are strongly attracted to the stationary phase will not move very far
chemicals that are weakly attracted to the stationary phase will move: A) further up the paper B) not very far
A) chemicals that are weakly attracted to the stationary phase will move further up the paper
remember a pure substance will produce a single spot in ALL solvents
• a pure substance will produce a single spot in ALL solvents
chemicals in a mixture may separate into different spots depending on the solvent
chemicals in a mixture may separate into different spots depending on the solvent
why do we draw the starting line in pencil
pen ink would move up the paper with the solvent
testing for gases describe how to test for hydrogen gas?
• remove the bung of the test tube and bring a burning splint towards mouth of test tube. hydrogen will burn rapidly and produce a squeaky pop sound
describe how to test for oxygen gas?
• bring a glowing splint towards the mouth of the test tube - if the splint relights then oxygen gas is present
describe how to test for carbon dioxide gas
• draw up some gas into a plastic pipette. • bubble gas through test tube • if limewater turns cloudy then carbon dioxide is present
describe how to test for chlorine gas
-bring damp litmus paper into mouth of test tube chlorine would bleach the damp litmus paper white
what is limewater? ( could ask in exam)
limewater is an aqueous solution of calcium hydroxide
Flame tests- how does it work explain steps briefly
1) First we place a small amount of our chemical onto a wire mounted in a handle 2) place end of this into a roaring (blue) bunsen burner flame 3) the colour of the flame can help us identify the metal ion