IGCSE CHEMISTRY PAPER 6 revision
1) What is the purpose of ice or cold water? To To cool down the gas so that tha t it condenses and turns into a liquid. 2) when the gas collecting tube is upside down, give a property of this gas. It is less dense than air. air. ) Why is a pencil used us ed in drawing thenorigin line in chro!atography? chro!atography? If pen was used, it ill dissolve giving colours and so, the e"peri!ent e"peri!ent won#t be accurate. $) When using ethanol, give a better apparatus arrange!ent, and why? %over apparatus wth a lid, because ethanol is volatile. &) In the tests and observation tables, when in the 'rst row, they tell you that upon heating condensation occured, there there will be a question as(ing what does this show about the solid? It is hydrated. ) when copper is used in the test, and the answer is four !ar(s, the best answer is* light blue precipitate +ppt) which is soluble in e"cess to for! dar( blue solution. ) Why is this e"peri!ent done in a fu!e cupboard? It releases har!ful gases that are poisonous. It is to"ic. -) Which result appears to be inaccurate? It is the point not appearing on the drawn graph, you read it#s "a"is and write it with a reason indicating that it doesn#t occur in the graph. /) Why should the solid be crushed? It increases surface area for a faster rate of reaction. 10) Why is the e"peri!ent !ade in a wellventilated roo!? To prevent the burning of the substance. 11) e"plain the ter! +decant). ilter3 ilter3our our the liquid leaving the solid s olid alone. 12) Why is concentrated sulphuric acid not used to dry a!!onia? 4ecause it will react with the base a!!onia, which is neutrali5ation reaction. 1) Why should sa!ples be ta(en fro! di6erent parts of the 'eld? To get !ore accurate results. 1$) 7uggest why it is i!portant to (now the p8 of the soil. To To see which is the best place for growing, and wht (ind of base to use for neutrali5ing it. 1&) What is necessary for rusting? Water +hu!idity) and o"ygen +air). 1) 7uggest why in an e"peri!ent e"peri!ent for rusting the water level increases. 9"ygen is used up, and water is used to ta(e its place. 1) or electrolysis, electrolysis, state the observations. The bulb will light : !etal is for!ed on the cathode i55 of gases produced. 1-) 7uggest a suitable !aterial for electrodes. ;raphite %arbon 7teel.
1/) when copper o"ide is reacted with hydrogen, what is the colour change? 4lac( to brown, because copper o"ide is reduced to copper. 20) 8ow can you distinguish between water and ethanol? e!ove the delivery tube fro! water to prevent suc(bac(. 2&) In rate of reactions, always include the word collisions between particles. 2) 8ow can you distinguish between al(anes and al(ane? @ust add hydrochloric acid, in which nothing happens with sulphate, but a '55 or e6ervescence of carbon dio"ide will occur with carbonate. 2/) When a !easuring cylinder is used, and they as( for a change in apparatus to get !ore reliable results, you should say that a biuret can be used instead as it is !ore accurate. 0) volu!e of reagent used decreases if it is !ore concentrated. 1) in an e"peri!ent observation of p8 value, and they as( what type of acidbase is used, your answer should be weather wea( or strong. : strong acid lies between p8 values of 0 and 2, and a wea( one lies between and . is neutral. : wea( base lies between - and 11, while a strong one lies between 12 and 1$. 2) : concentrated acid is an acid that contains a large nu!ber of 8A, hydrogen ions. Bice versa with dilute acid. ) : concentrated base is a base that contains a large nu!ber of 98# hydro"ide ions. Bice versa with dilute base.
$) a strong acid is one that ioni5es co!pletely giving 8A in solutions. Bice versa with a wea( one.. &) : strong base is one that ioni5es co!pletely giving 98 in solutions. Bice versa with a wea( one.. ) %oncentrated* is a solution that contains a large nu!ber of solute or little a!ount of water is involved. ) 8ow can you !a(e crystals? 1)heat till point of crystalli5ation. 2) leave to cool gradually. ) 'lter, dry and collect the crystalsC -) 8ow can you detect the point of crystalli5ation? 3lace a stirring rod in the solution and see the for!ation of the 'rst crystals on it. /) When you crush, you use a pestle and !ortar. $0) ;rass is ground with ethanol rather than water because clorophyll is !ore soluble in ethanol. $1) %olour of rusty iron 'llings is brown +orange and red are I thin( accepted) $2) If pure o"ygen was used instead of air, rusting will be faster. $) you can speed up the drying process by using a fan or by increasing te!perature or by using a hairdrier if you have one ) , D9T a catalyst. $$) The action of a lie big condenser is to change stea! to water. $&) to chec( for the purity for a collected solvent, test it#s !elting or boiling point. $) The chro!atogra! needs to be sprayed with locating agent is a!ino acids are investigated because they are colorless. $) If water contained salt, this will have no e6ect on rusting, however if a bigger substance is being rusted, it will be slower. $-) 8ydrated copper sulphate will turn fro! blue to white upon heating. $/) saturated* no !o solute can be dissolved in a solvent :T : %9D7T:DT TEF3E>:T<>E.. &0) :n e"cess a!ount of reactant is used to !a(e sure all the other reactant will be used. &1) 7o!eti!es, crystals are dried using 'lter paper instead of heating to prevent the co!plete loss of water fro! crystals, and to prevent crystals fro! brea(ing. &2) how could you (now which reactant is in e"cess? :t the end of the reaction, the e"cess reactant will be visible. &) e"cess !eans !ore than what is needed. &$) when lead bro!ide is used, you can use a fu!e cupboard or use goggles,lab coat,gloves,,, because it is to"ic.
&&) to separate two di6erent solutions with di6erent boiling point, use fractional distillation. &) 3hysical test of water* heat, it will boil at 100 degrees %elsius, or heat ice and it will !elt at 0 degrees %elsius. &) che!ical test of water* :dd blue cobalt chloride paper, it turns pin( 9> add anhydrous copper sulphate, it turns blue. &-) 're will be produced if alcohol is touched with lighted splint, therefore a water bath should be used when heating it. Gagging or cloth can be used to control te!perature for accurate results. &/) unreacted reactant is called e"cess. 0) :s reactants are heated, the particles gain energy, !ove faster, and their (inetic energy increases therefore there will be !ore collisions and rate increases.
