combined sci (chem) practical notes

chem

science (chem,phy) practical notes Chemistry Possible Practicals (non-exhaustive, from syllabus) 1 Qualitative Analysis 2 Speed of Reaction 3 Measurement of Temperature (Chemical Energetics) 4 Investigations 5 Filtration 6 Paper Chromatography 7 Quantitative Experiments Possible Topics Tested (Theory) Topic 1.1 Choosing suitable apparatus Topic 1.2 Separation Techniques Topic 4.2 Mole Concept Topic 5 Acids & Bases Topic 7 Redox Reactions Topic 8.2 Halogen Displacement Reactions Topic 8.3 Metal Displacement Reactions (Reactivity Series) Topic 9 Exothermic and Endothermic Reactions Topic 10 Rate of reactions Apparatus Record as… Metre Rule 0.1 cm Electronic Balance 0.1 g 0.01 g Digital Stopwatch 1 s Measuring Cylinder 0.5 cm 3 Burette 0.05 cm 3 Pipette Follow exact value Thermometer (-10 ~ 110°C) 0.5°C made by @javierererie

science (chem,phy) practical notes NOTE: Understanding the reactions that take place may help in answering questions. Redox Reactions ● Oxidation – intensifying colour ○ e.g banana becomes brown when left ● Reduction – fading colour ○ e.g bleaching of clothes Test for reducing agent: Acidified potassium manganate(VII) solution ● solution changes colour from purple to colourless Test for oxidising agent: Potassium iodide solution ● solution changes colour from colourless to brown ○ iodine confirmed with starch test, turn blue-black Qualitative Analysis: ● QA table will be provided during the exam. ● ‘add till in excess/no further change’ → at least ¾ of the test tube Cation test: ● bring marker to label test tubes ● do not add too much alkali at a time → may miss on any ppt ● record colour of ppt & whether it dissolves in excess alkali ● if dissolve, record colour of formed solution Anion test ● same thing Example of recording(s): ● A (colour) ppt is formed, insoluble in excess (compound) ● A (colour) ppt is formed, soluble in excess to form (colour) solution ● A pungent gas is produced, turns moist red litmus paper blue. Ammonia gas is produced ● Bubbles are formed, gives white ppt with limewater. Carbon dioxide gas is produced. ● A white ppt is formed. ● Bubbles are formed, extinguishes a lighted splint with a pop sound. Hydrogen gas is produced. ● A (colour) solid is deposited ● (colour) solution turns (colour) ● Test tube feels warm as the reaction is exothermic . ● Bubbles are formed, relights a glowing splint. Oxygen gas is produced ● No observable change Gas test ● CO2, don't add too much limewater as it will take longer for reaction to take place ○ use dropper pipette to take in co2 and then deposit inside the limewater ● Recording: ○ Observation: effervescence is observed. (colour) and (odour) gas is produced. ○ Gas confirmation test (use qa) ○ Identification of gas (use qa) made by @javierererie

science (chem,phy) practical notes Answering conclusion questions (open-ended stuff) ● use chemical formula of ion (e.g. Cu 2+ ) or name of ion (e.g. Copper(II) ion) ● evidence – give test conducted, followed by results ○ e.g. When sodium hydroxide is added to solution P (test conducted) , a blue ppt is formed, insoluble in excess sodium hydroxide (results) . Chem Energetics ● Final > Initial or +ve Temp Change – exothermic reaction ● Final < Initial or -ve Temp Change – endothermic reaction Rate of reaction: collision theory ● Inc temp / inc conc / dec particle size (eg powdered) – increase in ROR ● Dec temp / dec conc / inc particle size (eg granules) – decrease in ROR Metal Displacement ● Group 17: Flourine, Chlorine, Bromine, Iodine ● Recording if displaced ○ The (solution original colour) turns (new colour) ○ A (solid colour) is deposited ○ Test tube feels warm (if exothermic reactions) ● Recording if not displaced ○ No observable change / No visible change (better to go with the former) Dry Heating (of solid): ● gentle heating ○ hold bottom part at hottest part of flame (tip of blue cone) for 1s ○ remove for 2s, repeat for at least 15x ● strong heating ○ decomposes compounds, gases given off (test) and residue usually left over ● recording ○ change of solid colour ■ (colour) solid turns (colour) ○ change of state, s → L ■ (colour) solid melts to form (colour) liquid ■ water droplets observed at the side of the test tube ○ change of state L → s ■ liquid solidifies to form (colour) solid ■ water droplets observed at the side of the test tube ○ further change of colour ■ solid/liquid turns (colour) on further heating ○ final product upon cooling ■ (colour) residue formed on cooling ○ gas test obsv + identity (ref above) made by @javierererie

credits

credits for those who helped me make these during o-level period (in 2025!): ● my friends ● my school notes ● some of grail’s notes! document is separated into two: ● combined sci ( chem ) practical notes ● combined sci ( phy ) practical notes all the best for your practical!