Chemistry ATP Notes O Level PDF

Study Guide Chemistry (Paper 6) -0620- Caienotesofficial.com By: TooMuch1995 1 Contents of the book General Information...........................................................................................................................

Study Guide Chemistry (Paper 6) -0620- Caienotesofficial.com By: TooMuch1995 1 Contents of the book General Information.............................................................................................................................03 Test for Water......................................................................................................................................04 Basic knowledge of.Electrolysis...........................................................................................................04 Chemical Analysis................................................................................................................................06 Labelling of Apparatus..........................................................................................................................08 Salt Preparation: Soluble Salts.............................................................................................................10 Salt Preparation: InsolubleSalts...........................................................................................................15 Rates of reaction..................................................................................................................................16 Fermentation.......................................................................................................................................18 Frequent questions..............................................................................................................................18 Caienotesofficial.com 2 General Information As Per the syllabus of Cambridge IGCSE (0620) for Chemistry it’s your third Paper which you have chosen to appear for instead of the coursework or the practical test.  It’s Called Alternative to practical paper (ATP)  Its duration is for one hour only  It’s weighted at 20% of total available marks Caienotesofficial.com 3 Test for Water Not all Colourless liquids are water; therefore there is a test for identification and purity. It can be detected by using:-  Anhydrous copper(II) Sulphate  Anhydrous cobalt (II)Chloride Water will turn anhydrous copper (II) Sulphate from white to blue Water will turn anhydrous cobalt (II) Chloride from blue to pink Cobalt chloride paper contains blue anhydrous cobalt chloride which turns pink with presence of water To decide if water is pure or not, you would need to test that the boiling is 100oC exactly A Solid pure substance has a Sharp Melting point (as in Ice form of water) Electrolysis Electrolysis is the process of electrically inducing chemical changes in a conducting melt or solution example: splitting an ionic compound into the metal and non-metal. Caienotesofficial.com 4  Electrons flow from the battery to the cathode  Positive ions ( Metallic or Hydrogen ) in the liquid are attracted to this negative electrode  The positive ions accept electrons from the cathode, and metals or hydrogen are formed at the cathode.  Electrons flow from the anode to the battery or power supply  Negative ions (non- metals except hydrogen) are attracted to this positive electrode  When the electrode is inert ( carbon or platinium ) the negative ions lose electrons to the anode  Electrolysis separates an ionic compound back to the elements that form it. For example by electrolysis we can obtain sodium and chlorine from sodium chloride.  When the current is turned on, the negative ion in the electrolyte gets attracted to the positive electrode because they are oppositely charged. When this happens, the negative ion loses the electrons it gained from the positive ion during bond formation and becomes an atom. The electrons lost are transferred through the wire in the outer circuit from the anode to the cathode. At the same time, the positive ion from the electrolyte is attracted to the cathode, where it gains the electrons lost by the negative ion and becomes an atom too.  In ionic compounds the positive ion is a metal and it is collected at the cathode. And the negative ion is a non-metal and collected at the anode.  The electrons are transferred from the anode to the cathode through the wires. Caienotesofficial.com  The electrolyte is an ionic compound either in its molten or aqueous form. Ionic compounds conduct electricity only when they are in these forms because they contain free mobile ions which can carry the current but they don’t in solid form. 5 Chemical Analysis The following Test Analysis Should be learnt by heart as they are asked frequently in the exam.  Flame test colour  Test for gases  Test for positive ions (Cations)  Test for negative ions (anions) Some flame test Colours Metal Ions Formula Colour of flame + Sodium Na Yellow Potassium K+ Lilac Calcium Ca2+ Brick red Lithium Li+ crimson Copper Cu2+ Blue-green Barium Ba2+ Apple green Test for gases Gas Description Test Test result Ammonia (NH3) Colourless and Hold damp red litmus Indicator paper turns blue pungent smell paper (or universal indicator) in gas Carbon dioxide (CO2) Colourless and Bubble gas through White precipitate of calcium odourless lime water (calcium carbonate formed (solution hydroxide solution) turns milky) Chlorine (Cl2) Pale green, chocking Hold damp litmus Indicator paper is bleached smell paper ( or universal white (blue litmus will turn indicator) in gas red first) Hydrogen (H2) Colourless, odourless Hold a lighted splint in Hydrogen burns with a pop gas squeaky sound Oxygen (O2) Caienotesofficial.com Colourless, odourless Hold a glowing wooden splint in gas The splint re-lights 6  Test for negative ions (anions) Negative ion Test Test results Carbonate (CO32-) Add dilute hydrochloric acid to Effervescence (fizzes), carbon solid dioxide produced ( test with lime water) Chloride Acidify solution with dilute White precipitate of silver (in solution) (Cl-) nitric acid, then add aqueous chloride formed, precipitate silver nitrate soluble in ammonia solution Bromide Acidify solution with dilute Cream precipitate of silver (in solution) (Br-) nitric acid, then add silver bromide, only slightly soluble in nitrate ammonia solution Iodide Acidify solution with dilute Yellow precipitate of silver (in solution) (I-) nitric acid, then add aqueous iodide formed insoluble in silver nitrate ammonia solution Sulphate Acidify solution with dilute White precipitate of barium (in solution) (SO42-) hydrochloric acid , then add sulphate formed barium chloride solution Nitrate Make solution alkaline with Ammonia gas given off (test (in solution) (NO-3) sodium hydroxide solution then with moist red litmus) add aluminium foil and warm carefully Test for positive ions (Cations) Positive ion (in solution) Effect of adding Sodium Effect of adding Hydroxide ammonia solution Ammonium (NH+4) Ammonia produced on warming (test - with damp red litmus paper) Copper(II) (Cu2+) Light blue gelatinous precipitate of Light blue gelatinous copper hydroxide, insoluble in excess precipitate; dissolves sodium hydroxide giving a deep blue solution Iron (II) (Fe2+) Green gelatinous precipitate of Iron (II) Green gelatinous hydroxide insoluble in excess precipitate, insoluble in excess Iron (III) (Fe3+) Rust-brown gelatinous precipitate of Rust-brown gelatinous 2+) Caienotesofficial.com Iron (III) hydroxide, insoluble in excess precipitate, insoluble in excess Calcium (Ca White precipitate of calcium hydroxide, No precipitate ( or only insoluble in excess very slight precipitate) Magnesium (Mg2+) White precipitate of magnesium White precipitate , hydroxide, insoluble in excess insoluble in excess Zinc (Zn2+) White precipitate of zinc hydroxide, White precipitate , insoluble in excess soluble in excess Aluminium (Al3+) White precipitate of aluminium White precipitate , hydroxide, soluble in excess giving a insoluble in excess colourless solution 7 Apparatus you will have to name and Describe # Name Description 1 Beaker Used to hold and heat liquids. Multipurpose and essential in the lab. 2 Bottle Bottles can be used for storage, for mixing and for displaying. 3 Bunsen Bunsen burners are used for heating and exposing Burner items to flame. They have many more uses than a hot plate, but do not replace a hot plate. 4 burette The burette is used in titrations to measure precisely how much liquid is used. 5 Crucible Crucibles are used to heat small quantities to very high temperatures. 6 Erlenmeyer The Erlenmeyer Flask is used to heat and store liquids. Flask The advantage to the Erlenmeyer Flask is that the bottom is wider than the top so it will heat quicker because of the greater surface area exposed to the heat. 7 Evaporating The Evaporating Dish is used to heat and evaporate Dish liquids. 8 Florence Flask The Florence Flask is used for heating substances that need to be heated evenly. The bubbled bottom allows the heat to distribute through the liquid more evenly. The Florence Flask is mostly used in distillation experiments. 9 Food Food Colouring is used in many experiments to show Colouring colour change and to make the experiment more exciting. 10 Caienotesofficial.com Funnel The Funnel is a piece of equipment that is used in the lab but is not confined to the lab. The funnel can be used to target liquids into any container so they will not be lost or spilled. 11 Micro spatula The Micro spatula, commonly called a spatula, is used for moving small amounts of solid from place to place. 12 Mortar and The Mortar and Pestle are used to crush solids into Pestle powders for experiments, usually to better dissolve the solids. 8 13 Paper Towels Paper Towels are essential to the lab environment. They will be used in almost every lab. 14 Pipet The pipet is used for moving small amounts of liquid from place to place. They are usually made of plastic and are disposable 15 Ring Stand Ring stands are used to hold items being heated. Clamps or rings can be used so that items may be placed above the lab table for heating by bunsen burners or other items. 16 Stir Rod The stir rods are used to stir things. They are usually made of glass. Stir Rods are very useful in the lab setting. 17 Stopper Stoppers come in many different sizes. The sizes are from 0 to 8. Stoppers can have holes for thermometers and for other probes that may be used. 18 Test tube The test tube brush is used to easily clean the inside of Brush a test tube. 19 Test tube The holder is used to hold test tubes when they are hot Holder and untouchable. 20 Test tube Rack The test tube rack is used to hold test tubes while reactions happen in them or while they are not needed. 21 Thermometer The thermometer is used to take temperature of solids, liquids, and gases. They are usually in oC, but can also be in oF 22 Tongs Tongs are used to hold many different things such as flasks, crucibles, and evaporating dishes when they are hot. 23 Triangle The triangle is used to hold crucibles when they are being heated. They usually sit on a ring stand 24 Caienotesofficial.com Volumetric The Volumetric flask is used to measure one specific Flask volume. They are mostly used in mixing solutions where a one litter or one half a litter is needed. 25 Watch Glass The watch glass is used to hold solids when being weighed or transported. They should never be heated. 9 Salt Preparation Here are a few general points on Salts:  Salts are ionic Compounds  A Salt compound is formed from an acid by the replacement of hydrogen in the acid by a metal How is salt produced? Salt deposits were formed by the evaporation of ancient seas millions of years ago therefore Solid rock salt is directly mined from those areas. Another technique known as solution mining in which the salt is dissolved underground and the solution. This solution is known as the brine solution and it’s pumped to the surface Preparing Salts Number 1: you should know that there are two types of salts  Soluble Salts  Insoluble Salts Number 2: you should know that each has a different way of producing Number 3: When preparing a Salt, you should keep two things in your mind  Is the salt soluble or insoluble in water?  Do crystals of the salt contain water of crystallisation? These points influence the preparation method chosen and how crystals are handled at the end of the experiment Preparing Soluble Salts Number 4: Soluble Salts can be made by either  Characteristic Reaction ( with base or carbonate or metal)  Titration Method (involves neutralisation) The three Characteristic Reactions Caienotesofficial.com Soluble Salts are prepared using a  Insoluble Solid  Dilute Acid The Insoluble solid can be one of those three  A Metal  A Base  A Carbonate Number 5: Remember that the acid you use (parent acid) affects what type of salt you get 10   To make chloride Salts use Hydrochloric Acid  To make Nitrate Salts use Nitric Acid  To make Sulphate Salts use Sulphuric Acid  To make Ethanoate Salts use Ethanoic Acid Reacting dilute acid with fairly reactive metal Dilute Acid + Metal Metal Salt + Hydrogen gas Reacting dilute acid with insoluble base Dilute acid + Insoluble base Metal Salt + Water Reacting dilute acid with insoluble Carbonate Dilute acid + Insoluble Carbonate Metal Salt + Water + Carbon dioxide Steps of Preparing (using Characteristic Reactions Method) Step 1: Add Excess of the insoluble Solid to the dilute acid in a beaker until reaction stops (no fizzing) Step 2: The Excess Solid is filtered out and collect the filtrate Caienotesofficial.com 11 Step 3: The Filtrate is gently evaporated to concentrate the Salt solution This can be done using a water bath Step 4: When Crystals are seen Forming, heating is stopped Step 5: The concentrated solution is left to cool to from crystals completely Step 6: The crystals are filtered off and washed with distilled water Step 7: Caienotesofficial.com Dry crystals between filter papers The Titration Method Reacting dilute Acid with soluble Base (Alkali) Dilute acid + Alkali Metal Salt + Water This involves the neutralisation of acid with an alkali (to produce a soluble Salt) Number 6: Since both the reactants are colourless an indicator should be used 12 Steps of Preparing (using the titration method) Step 1: Fill the Burette with the dilute acid till the zero mark Step 2: A known value of an alkali is placed in a conical flask using a pipette Step 3: Caienotesofficial.com Add few drops of indicator to the conical flask of alkali (Methyl orange will be used as an example here) Step 4: The acid solution is run from the burette to the flask conating alkali until indicator colour changes 13 (Methyl orange will turn pink here) Step 5: The Volume of acid used to neutralise the alkali is noted Step 6: The process is repeated with the volume noted from the acid and same volume of alkali but this time without the addition of the indicator Step 7: Evaporate most of the solution using a water bath Caienotesofficial.com 14 Step 8: When crystals are seen stop heating, and leave it to cool then dry between filter paper Preparing Insoluble Salts Insoluble salts are prepared by mixing 2 soluble salts together, each containing half the needed salt. This process is called precipitation. Example: Preparation of insoluble lead sulphate (PbSO4): Step 1: Choose 2 suitable soluble salts, e.g. lead nitrate and sodium sulphate. Make aqueous solutions of both. Step 2: Mix the two aqueous solutions together. An insoluble precipitate of lead sulphate is formed. Step 3: Filter the solution formed to get lead sulphate in filter paper. Step 4: Caienotesofficial.com Wash the filter paper with distilled water to remove trace of soluble salt. Step 5: The filter paper is dried in a warm oven. The salt is then scraped off it. 15 Rates of reaction Caienotesofficial.com 16 Caienotesofficial.com 17 Fermentation You should know about Fermentation fully (only Definition is provided here) Definition: It is an anaerobic process. It takes place under condition where there is no air or oxygen available. Therefore, there is no oxygen (O2) present in the equation for the reaction taking place. Carbon dioxide is the gas produced in the reaction. Separation Techniques The most common ones are: Filtration Distillation (fractional and normal one) Chromatography Precipitation You should know about the above all too Frequent Questions In this Section, there will be a collection of 60 questions from the past paper exams of paper 6 which are repeated every year. It would be a great help for you if you try to read and understand them because they also might come in a different way (Indirectly) Caienotesofficial.com They are numbered for you from 1-60 to make it easier for you Question 1: What is the purpose of ice or cold water? Answer: To cool down the gas so that it condenses and turns into a liquid. Question 2: When the gas collecting tube is upside down, give a property of this gas. 18 Answer: It is less dense than air. Question 3: Why is a pencil used in drawing the origin line in chromatography? Answer: because pencil will dissolve as it will not give collies which makes the experiment more accurate Question 4: When using ethanol, give a better apparatus arrangement, and why? Answer: Cover apparatus with a lid, because ethanol is volatile. Question 5: In the tests and observation tables, when in the first row, they tell you that upon heating condensation occurred, there will be a question asking What does this show about the solid? Answer: It is hydrated. Question 6: When copper is used in the test and the answer is four marks, (the best answer is...) Answer: light blue precipitate (ppt.) which is soluble in excess to form dark blue solution. Question 7: Why is this experiment done in a fume cupboard? Answer: It releases harmful gases that are poisonous. It is toxic. Question 8: Which result appears to be inaccurate? ( In graph drawing) Answer: It is the point not appearing on the drawn graph, you read its x-axis and write it with Caienotesofficial.com a reason indicating that it doesn't occur in the graph. Question 9: Why should the solid be crushed? Answer: It increases surface area for a faster rate of reaction. Question 10: Why is the experiment made in a well-ventilated room? 19 Answer: To prevent the burning of the substance. Question 11: Explain the term (decant) Answer: Filter/Pour the liquid leaving the solid alone. Question 12: Why is concentrated sulphuric acid not used to dry ammonia? Answer: because it will reach the base ammonia, which is neutralization reaction. Question 13: Why should samples be taken from different parts of the field? Answer: to get more accurate results. Question 14: Suggest why it is important to know the pH of the soil. Answer: to see which is a better place for growing, and what kind of base to use for neutralizing it. Question 15: What is necessary for rusting? Answer: water (humidity) and oxygen (air). Question 16: Suggest why in an experiment for rusting the water level increases. Answer: Oxygen is used up, and water is used to take its place. Question 17: Caienotesofficial.com For electrolysis, state the observations. Answer: The bulb will light - A metal is formed on the cathode - Fizz of gases produced. Question 18: Suggest a suitable material for electrodes. Answer: Graphite - Carbon – Steel- Platinum. Question 19: 20 When copper oxide is reacted with hydrogen, what is the colour change? Answer: black to brown, because copper oxide is reduced to copper. Question 20: How can you distinguish between water and ethanol? Answer: use cobalt chloride paper, it turns from pink to blue with water, but there will be no change with ethanol. Question 21: How can you distinguish between sulphuric acid and aqueous sodium sulphate? Answer: there are three tests, you can use a metal carbonate in which carbon dioxide will be produced with sulphuric acid but there will be no change with sodium sulphate. You can add a metal, in which hydrogen is produced with sulphuric acid, but no change in sodium sulphate. Finally, you could use an indicator like litmus paper, it will change to red with sulphuric acid, but there will be no change with sodium sulphate.. Question 22: How can you distinguish between hydrochloric acid and nitric acid? Answer: add silver nitrate, in which white ppt. will be formed with hydrochloric acid, but there will be no reaction with nitric acid. Question 23: What is the purpose of the mineral wool? Answer: to absorb and hold the liquid. Question 24: When there is a delivery tube involved in a question, what precaution should be taken in the experiment when the heat is removed? Answer: remove the delivery tube from water to prevent suck-back. Question 25: Caienotesofficial.com In rate of reactions, always include the word "collisions between particles". Question 26 How can you distinguish between alkanes and alkenes? Answer: Use bromine water, in which the alkene will decolourise it to colourless, but nothing, happens with an alkane, 21 Question 27 How can you distinguish between chlorine and sodium chloride? Answer: add litmus paper, it will bleach with chlorine, but nothing happens to it with sodium chloride. Question 28 How can you distinguish between copper sulphate and copper carbonate? Answer: acidify with hydrochloric acid, and add barium chloride, there will be white ppt with sulphate, but no white ppt. with carbonate. OR just add hydrochloric acid, in which nothing happens with sulphate, but a fizz or effervescence of carbon dioxide will occur with carbonate. Question 29: When a measuring cylinder is used, and they ask for a change in apparatus to get more reliable results, Answer: you should say that a biuret can be used instead as it is more accurate. Question 30: Why Volume of reagent is used? Answer: volume of reagent used decreases if it is more concentrated. Question 31: In an experiment observation of pH value, and they ask what type of acid/base is used, your Answer: should be weather weak or strong. A strong acid lies between pH values of 0 and 2, and a weak one lies between 3 and 6. 7 are neutral. A weak base lies between 8 and 11, while a strong one lies between 12 and 14. Question 32: What is a concentrated acid? Caienotesofficial.com Answer: a concentrated acid is an acid that contains a large number of H+, hydrogen ions. Vice versa with dilute acid. Question 33: What is a concentrated base? Answer: a concentrated base is a base that contains a large number of OH-' hydroxide ions. Vice versa with dilute base. Question 34 22 What is a strong acid? Answer: a strong acid is one that ionizes completely giving H+ in solutions. Vice versa with a weak one. Question 35: What is a strong base? Answer: a strong base is one that ionizes completely giving OH- in solutions. Vice versa with a weak one. Question 36: What is meant by the term Concentrated? Answer: concentrated: is a solution that contains a large number of solute or little amount of water is involved. Question 37: How can you make crystals? Answer: 1) heat till point of crystallization. 2) Leave to cool gradually. 3) Filter, dry and collect the crystals! Question 38: How can you detect the point of crystallization? Answer: Place a stirring rod in the solution and see the formation of the first crystals on it. Question 39: What is used to crush a substance? Answer: when you crush, you use a pestle and mortar. Question 40 Caienotesofficial.com Why ethanol is used but not water? (grass) Answer: grass is ground with ethanol rather than water because chlorophyll is more soluble in ethanol. Note 41: Colour of rusty iron fillings is brown (orange and red are I think accepted) Note 42: If pure oxygen was used instead of air, rusting will be faster. 23 Note 43: You can speed up the drying process by using a fan or by increasing temperature or by using a hair-drier if you have one) NOT a catalyst. Note 44: The action of a lie big condenser is to change steam to water. Note 45: To check for the purity for a collected solvent, test it's melting or boiling point. Note 36: The chromatogram needs to be sprayed with locating agent is amino acids are investigated because they are colourless. Note 37: If water contained salt, this will have no effect on rusting, however if a bigger substance is being rusted, it will be slower. Note 38: Hydrated copper sulphate will turn from whit to blue upon heating. 49) Saturated: no more solute can be dissolved in a solvent AT A CONSTANT TEMPERATURE. 50) An excess amount of reactant is used to make sure all the other reactant will be used. 51) Sometimes, crystals are dried using filter paper instead of heating to prevent the complete loss of water from crystals, and to prevent crystals from breaking. 52) How could you know which reactant is in excess? At the end of the reaction, the excess reactant will be visible. Caienotesofficial.com 53) Excess means more than what is needed. 54) When lead bromide is used, you can use a fume cupboard or use goggles, lab coat, gloves because it is toxic. 55) To separate two different solutions with different boiling point, use fractional distillation. 56) Physical test of water: heat, it will boil at 100 degrees Celsius, or heat ice and it will melt at 0 degrees Celsius. 24 57) Chemical test of water: Add blue cobalt chloride paper, it turns pink OR add anhydrous copper sulphate, it turns blue. Question 58 Why is it dangerous to heat alcohol directly? Answer: fire will be produced if alcohol is touched with lighted splint, therefore a water bath should be used when heating it. Lagging or cloth can be used to control temperature for accurate results. Question 59 What is the name given to unreacted material? Answer: unreacted reactant is called excess. Question 60 What happens to the particles when they get heated? Answer: the particles gain energy, move faster, and their kinetic energy increases therefore there will be more collisions and rate increases. DONE Pray for me Caienotesofficial.com 25