Summer assessment 1 Flashcards
solid to liquid?
melting
liquid to solid?
freezing
liquid to gas?
evapourating
gas to liquid?
condensing
solid to gas?
subliming
What are elements?
consist of only one type of atom only
What is a compound?
a substance that is made of two or more differant elements which are chemically joined together
What is a mixture?
no chemical bonds between different parts of a mixture – can be seperated out by physical methods
What is a pure substance?
- if it is completely made up of a single element or compound
What does every pure substance have?
a specific melting and boiling point
What is an impure substance?
it will melt or boil gradually over a range of temperatures
When is filtration used?
to separate an insoluble solid from a liquid,
purification
Explain process of filtration?
put filter paper into a funnel and pour your mixture into it
- liquid runs through and solid residue is left behind
What is crystallisation?
seperates a soluble solid from a solution
Explain crystallisation?
- pour solution into an evapourating dish and gently heat solution. some water will evaporated and solution becomes more concentrated
- once some water has evaporared crystals start to form, remove from heat and leave to cool
- salt should start to form crystals as it becomes insoluble
- filter crystals out of the solution and leave in warm place to dry
- can use drying oven or a desiccator
What can you use to separate rock salt?
filtration and crystallisation
Explain rock salt?
simply a mixture of salt and sand - compounds but salt dissolves in water and sand doesnt
Process of seperating rock salt?
- grind with pestle and mortar
- dissolve in beaker
- filter through filter paper in funnel
- crystallise in evaporating dish
What is chromatography used for?
separate out mixtures
How does cromatography work?
- different dyes move at different rates
- some stick to paper and others will dissolve more readily
- distance dyes travel up paper depends on solvent and paper
How do you calculate RF?
distance travelled by solute/ distance travelled by solvent
What is Rf?
ratio between distance travelled by dissolved substance and the distance travelled by solvent
Why is chromatography used>
to see if a certain substance is present in a mixture
What are samples of pure substances called?
standard reference materials
What is distillation?
seperate mixtures that contain liquids
What are the two types of distillation?
simple and fractional
Explain process of simple distillation?
- solution heated, lowest boiling point part evaporated
- vapour is cooled and condenses and is collected
- rest of solution left in flask
Why is fractional distillation used?
if you have a mixture of liquids with similar boiling points
Explain process of fractional distillation?
- put mixture in flask and add fractioning column on top and heat it
- different boiling points mean will separate at different temps
- lowest boiling point seperatas first
- column is coolest at the top
- when first liquid has been collected, rise temp and wait until next one reaches top q
What are group 0 elements called?
noble gases
What are noble gases?
inert - dont react with much at all
What colour are noble gases?
colourless
Litmus paper colours?
red in acid
purple in neutral
blue in alkaline
Phenolphalein colours/
colourless in acid
bright pink in alkaline
Methyl orange colours?
red in acid, yellow in alkaline
Acid definition?
source of hydrogen ions, proton donors
Base definition?
substance that can neutralise an acid, proton accepters
Alkali definition?
soluble bases, source of hydroxide ions
What is neutralissation?
reaction between acid and base or alkali
Neutralistaion equation?
H+. +. OH- = H20
What four things does rate of reaction depend on?
- temperature
- surface area
- concentration
- catalyst
Explain increasing temperature?
- particles move faster, more collisions
- increases energy of collisions
- more successful collisions increasing rate
Explain increasing concentration?
- more liekly for collisions to take place as frequency increases
Explain surface area and rate?
- increase surface area to volume ratio
- more area to work on so frequency increases
What are theoretical yields?
calculated yield
What is actual yeild?
yield from experiment
How do you work out % yield?
actual yield / theoretical. x100
How do you make soluble salt?
using an acid that contains one of the ions you want in the salt and an insoluble base containing other ion
Describe steps in making a soluble salt?
- heat acid in water bath, in fume cupboard
- ad base to acid, produce soluble salt
- filter off excess to only get salt and water
- heat slightly to evaporate some water. leave to cool and crystallise
- filter off solid salt and leave to dry
What are the two ways of finding empirical formula?
combustion reaction and reduction reaction
How does combustion work?
- when substance reacts with oxygen
Explain how to find empirical formula with combustion?
- heat crucible till red hot - ensures clean
- leave to cool and weigh it
- add clean magnesium ribbon and reweigh
- heat crucible with lid on to stop parts escaping but with small gap fo oxygen
- heat around 10 mins or till magnesium white
- cool and reweigh
- mass of magnesium oxide is latest reading - initial reading
What is reduction?
loss of oxygen from substance
Explain how to do the reduction reaction?
- put rubber bung on test tube and weigh them
- then put small amount of copper oxide in middle of tube
- put bung in and reweigh
- place test tube sideways with bunsen underneath copper oxide and tube facing downwards
- expel air by turning on gas for 5 seconds
- light bunsen for about 10 mins or solid changes from black to brown- pink
- leave to cool
- weigh test tube
Explain an experiment for how temp effects rate of reaction?
- sodium thiosulfate and hydrochloric acid are both clear
- find rate by watching black cross disappear in cloudy sulfur
- repeat for differant temps by heating solution in water bath
Which experiment alows you to see the affect of catalysts on rate?
decomposition of hydrogen peroxide
Which catalysts are used in experiment of decomposition?
- manganese oxide
- copper oxide
- zinc oxide
WHat is given off in decompostion to tell us the rate?
oxygen gas
Describe steps in catalyst rate experiment?
- Set up conical flask filled with catalyst and hydrogen peroxide with bung and tube leading to syringe filled with oxygen
- measure volume at regular intervals in syringe
- repeat with same concentration and volume but differant catalyst
