C10 Chemical Analysis Flashcards
What is a pure substance
It is made up of just one substance
That can be either an element or a compound
How can you identify pure substances
Using boil8ng points and melting points
Pure substances have characteristic specific temperatures at which they melt and boil
Eg water melts at 0 and boils at 100c
The melting and boil8ng point of A mixture will vary depending on the composition of the mixture
How do impurities affect boiling point and melting point
Impurities tend to lower melting point and raise its boil8ng point
The more impurities the greater the difference from the fixed point of the pure substance
Eg purified caffeine melting range is 234-237c
Crude caffeine extracted fro tea is 180-220 showing it is impure
What is a formulation
A formulation is a mixture that has been designed to produce a useful product eg medicine or drugs
Potentially compromising 5-10% of the active drug that relieves the illness
Why are tablets containing sweeteners and smooth coatings
Why are there other fillers
To aid swallowing
To aid their dissolving at most effective place in digestive tract
What are paints and what do they contain
Formulations
Pigment to provide colour
Binder to help piano stick and form protective film when dry
Solvent to help pigment and binder spread well during painting by thinning them out
What are other typical formulation
Washing up liquid- includes surfactant (detergent), water to thin out, colour fragrance to improve appeal and rinse agentto help water drain off
Also fuels, alloys, pesticides, cosmetics, food products
What is an element
A pure substance that contains only one type of atom eg Argon, Au(gold), H2, F2, Cl2, S8
What is a compound
Two or more elements chemically bonded as a pure substance
Eg NaCl, H2O
What is an atom
Simplest pure chemical building block eg H
What is a mixture
Two or more elements or compounds not chemically bonded eg Air, sea water, orange juice
Not pure because not chemically bonded
What is a molecule
Two or more atoms joined by chemical bonds
What is an alloy
Mixture of two elements eg iron and carbon make steel
Is spring water pure?
No it is a mixture with several substances listed on the the label not just H2O
Why is salt placed on roads in winter months
It melts the ice because it creates a mixture with a lower range of freezing points much lower than ice/ water
Why is pure gold not suitable fi4 jewellery
It is very soft and bendy when pure
Why is gold alloy suitable
The alloy is harder because it contains different sized atoms that make it harder for layers to slide over each other
What is purity
The amount of a substance in a mixture
What is chromatography
Separating mixtures according to their solubility
What is the equation for retaining factor?
Distance substance travels ➗distance solvent front travels
How does chromatography work?
Different forms include Paper chromatography Thin layer chromatography- TLC column chromatography Gas chromatography
What are the 2 stages of chromatography
- Stationary phase - the part that does not move - paper
2 mobile phase - the part that moves - water or solvent
What is the process
Starting line drawn on paper in pencil so it doesn’t dissolve
Small spots of each sample placed on starting line
Paper left vertically in solvent but solvent is below level of spots
Solvent soaks up paper for few minutes until near top
Paper removed to dry
Substances separate because have different attractions to paper and solvent - ie if strong attraction to solvent = move a long way
What is the test for hydrogen
Use of hydrogen
Why does it pop
Lighted splint gives off squeaky pop
Eg Zinc + sulfuric acid => zinc surface + hydrogen
Used for fuel for vehicles
Pops because the lighted splint cause small explosion of hydrogen burning with oxygen
What is the test for oxygen
What is a use
Relighting a glowing splint
Hydrogen peroxide decomposing with manganese oxide catalyst makes water and oxygen
Helps with breathing
What is a test for carbon dioxide
What use
Limewater goes cloudy - puts out a lit splint
React marble chips/ calcium carbonate with dilute hydrochloric acid
Safety - wear eye protection
Use putting out fires
Test for chlorine
Use
Damp blue litmus paper bleached or turns white
Safety - toxic gas
Hydrochloric acid and potassium manganate crystals in boiling tube gives off chlorine gas
Killing bacteria
