experiments
scientific method
1 observe and question 2 create hypothesis 3 plan experiment 4 carry out experiment 5 analyse results 6 do results support hypothesis 7 share conclusion
skills used in experiments
thinking -observation -using apparatus -working accurately -mathematics -writing up
writing up an experiment
introduction
hypothesis
plan
experiment
results
analysis of results
conclusion
improving reliability
test for ammonia
hold damp red litmus paper to it and paper will turn blue
test for carbon dioxide
bubble through limewater limewater will turn milky
test for chlorine
collect gas and hold lit splint to it gas burns and squeals
test for oxygen
collect gas and hold glowing splint to it splint will burst into flames
test for sulfur dioxide
soak filter paper in potassium magnate and place it in gas paper will go from purple to colourless
flame test results for cations
red =lithium yellow =sodium lilac=potassium green=barium orange = calcium blue-green = copper
chemical tests for cations
ammonium ion - add aqueous sodium hydroxide to salt to drive off ammonium gas then test gas
metal cation - precipitate hydroxide - dilute aqueous sodium hydroxide to salt then observe colour or behaviour of precipate
test for halide ions
-add equal volumes of dilute nitric acid and silver nitrate to a solution -silver halides are insoluble so halides must be present for a precipate to form and the colour will reveal which one is present
halide ions colours
white -chloride ions cream -bromine ions yellow - iodine ions
test for sulfate ions
add equal volumes of dilute nitric and barium nitrate to solution -if sulfate ions are present precipate will form
test for sulfite ions
add acidified aqueous potassium magnate to solution -solution turns colourless if sulfite ions are present
test for nitrate ions
add dilute aqueous sodium hydroxide and aluminium foil -heat gently - if ammonia gas is given off nitrate ions are present
test for carbonate ions
add dilute hydrochloric acid -if solution gives off solution which makes limewater milky carbonate ions are present