EDEXCEL Chemistry Revision Notes PDF

EDEXCELL Final revision new syllabus (1-9) Dr. Anne MAHDY 1  STATE OF MATTER P.O.C. Solid Liquid Gas Difficult to Difficult to Ea...

EDEXCELL Final revision new syllabus (1-9) Dr. Anne MAHDY 1  STATE OF MATTER P.O.C. Solid Liquid Gas Difficult to Difficult to Easy to COMPRESSIBILITY compress compress compress MOLECULAR Very close Close Widely separated packing Fixed Take the shape Take the Shape of the container shape of the container Molecular Vibrate in its Free to move Free to position move movement Attraction force Very strong Relatively Very weak strong Diffusion Very slow Slow rapid THE KINETIC THEORY AND CHANGE OF STATE The main points of the kinetic theory are: All matter is made up of very small particles (different substances contain different types of particles such as atoms or molecules). The particles are moving all the time the higher the temperature, the higher the average energy of the particles). Heavier particles move more slowly than lighter particles at the same temperature. CHANGE OF STATE 1- Solid to liquid (melting) When a solid is heated the particles gain more kinetic energy and vibrate faster, to move slightly further apart When enough energy is given to the particles the forces between them are weaken and the solid melts and changes to liquid. The temperature at which this happens is called the melting point... DR. Anne Mahdy 2 2. Liquid to GAS (boiling) DR. Anne Mahdy When a liquid is heated the kinetic energy of the particles increases still further and the particles move faster and further apart till they overcome the forces holding them together. The particles can then escape from the liquid and move around (quickly and independently and the liquid is said lo boil at a steady temperature called the boiling point. Sufficient kinetic energy , some of the surface molecules change into vapour below the boiling point this is called evaporation When gas particles cool the opposite process happens. The gas particles move more and more slowly till they cannot overcome the attraction forces and so the gas condenses to a liquid. As the liquid particles get cooler, they move more & and more slowly and more forces of attraction are build up till the liquid FREEZES or SOLIDIFIES. 3-SOLID TO GAS Some solid substances do not form a liquid When heated. They change from a solid directly to a gas. Also when the gas is cooled, it condenses to a solid, not a liquid. This is called SUBLIMATION. Examples of substances that sublime are: Solid Carbon dioxide, iodine, iron (Ill) chloride, aluminum chloride and most ammonium salts. Diffusion: particles escape and spread out to move from high concentration to low concentration Diffusion (spread out) is affected by: Temperature: when temp. increase rate of diffusion increase. Mass no. when mass no. decrease rate of diffusion increase. 3 COMPARISON BETWEEN COMPOUND AND MIXTURE COMPOUND MIXTURE 1. Formed of two or more elements 1. Formed of clement and or in a fixed composition chemically compounds in any composition bonded not chemically bonded 2.. Made without a chemical 2. Made by means of a chemical reaction. reaction 3. Cannot be separated by a physical 3. Components can be process, a chemical reaction is separated by needed a physical process. 4. Has new properties different from 4. Has the properties of its elements its components PURE AND IMPURE SUBSTANCES IF an unwanted substance, mixed with the substance you want, is called an impurity; water may have particles of a harmful substance in it. So it is not pure and could make you ill. You can check melting and boiling points to test for purity. A pure substance has a definite, sharp, melting point and boiling point. When a substance contains an impurity its melting point falls and its boiling point rises - it melts and boils over a range of temperatures, not sharply. The more impurity there is,the bigger the change in melting and boiling points ( the wider the temperature range over which melting and boiling occur). Pure water melts at 0°C and boils at 100°C sharp temperature Water freeze around 0.5°C and boils around 101 °C. So it is not pure. To get a pure substance we should separate it from other impure substance mixed together DR. Anne Mahdy 4  DR. Anne Mahdy Separation of mixture: A) Solid/ Solid B)Solid in water Ex.1: Salt in sand 1) Insoluble solid in liquid steps by filteration 1- Dissolve in water 2) Soluble solid in liquid 2- Salt dissolves but sand remains. by simple distillation for water 3- Filter the mixture. Crystallization for salt using filter funnel and filter paper 4- Heat filtrate to remove water During dissolving we should heat and stir for faster and maximum solubility Ex.2: Iron in sulphur Step: 1- By magnet C)Mixture of liquid 1)Miscible liquids (also mix of gases) Ex.: Ethanol/ water Separate by fractional distillation in which 2 liquids are placed in a rounded bottom flask connected to a fractionating column and condenser. The 2 liquids boil and move up the column The 1 with the highest boiling point condensed in the column and return to the flask and the 1 with the lowest B.P. continuous to the condenser as separation depends on difference in boiling point. 2) Immiscible liquids Ex: Oil/ water By separating funnel 5  DR. Anne Mahdy D)Paper Chromatographer To separate mixtures of coloured materials to determine number of components in a mixture (Ex: to determine number of different dyes in ink) - Draw a baseline in pencil (because It is insoluble in any solvent) near the bottom of a rectangular sheet of chromatography (filter) paper. you should leave 2 from the base of the paper why? Enough space to add the solvent without touching the base line - Put a spot of the solution (ink sample) on the baseline - Place the paper in a beaker containing a very small amount of solvent (as water) so that the baseline is above the level of solvent why? To avoid dissolving the spot in the solvent Observation during chromatography - The solvent moves up the paper and separates the sample spot into different spots. The more soluble substance moves up higher than others. A spot that does not move up with the solvent is not soluble in it and we have to change the solvent. -If the spots are not coloured (ex: sugars or amino acids) a locating agent is sprayed on the spots after chromatography to make them visible R, value of a spot = distance traveld by spot (from base line) (mm). solvent front (distance travelled by solvent) (mm) After chromatography 6  SOLUBILITY Measurement of How Much of a Substance (solute) will Dissolve in a Given Volume of a Solvent (Shown in the Units of g per 100g of Solvent) If a Substance is Soluble, it will Dissolve in a Given Amount of Solvent (liquid) Solubility Increases as Temperature and Pressure Increases EXAMPLE OF INTERPRETING SOLUBILITY CURVES: SOLID EXPLANATION A As Temperature Increases, Solubility of Solid A Increases the Most B As Temperature Increases, Solubility of Solid B Increases but at a Slower Rate than Solid A C Temperature Does Not Affect the Solubility of Solid C SOLVENT: is a liquid which can be used to dissolve things 7  SOLUTE: is a substance which dissolves (mixes completely) in a solvent to make a solution. SATURATED SOLUTION: solution is formed when no more solute can dissolve at that temperature Explain why crystals are formed on cooling of solution? Because on cooling solubility decreases ( the solvent can no longer hold all the solute molecules they start to leave the solution and form solid crystals) D R filter FUNNEL. A n n e M a h d y M e a s u r i n g 8  Formula and EQUATIONS To write the state of matter for an equation you should know soluble and insoluble salts Soluble salts are 1- All salts of group 1 , ammonium salts , nitrate salts , all acids are (aq) 2- Group7 salts are soluble except if group7 salt are with Ag,Pb are solid 3- Sulfate salts are soluble except with Ag ,Ca, Ba and Pb form insoluble sulfates INSOLUBLE (SOLID SALTS) are 1- Any salt contains OXIDE , HYDROXIDE , CARBONATE except if these 3 are forming a salt with group 1 or ammonium 2- ALL SILVER AND LEAD SALTS are insoluble except these 2 form a salt with NITRATE will be soluble (aqueous ) ☺ On writing formula for an element copy its symbol from periodic table without numbers except (H,O,N,GROUP 7) should take 2 eg H 2,Cl2 For writing formula for IONIC compound we should swap valences Formula of some radicals Of valency 1 Ammoniun NH4+1 Nitrate NO3-1 Nitrite NO2-1 Hydroxide OH VALENCY 2 Sulfate SO4-2 Sulphite SO3-2 Carbonate CO3-2 DR. Anne Mahdy 9  Oxidation and reduction DR. Anne Mahdy Oxidation (reducing agent) Reduction (oxidizing agent) Gain of oxygen lose of oxygen Oxidation CuO + H2 = Cu + H2O Reduction Lose of electrons gain of electrons Increase in oxidation state decrease in oxidation state Reaction in which oxidation and reduction occurs called redox 10  Reactivity Series To arrange elements according to activity, we should carry displacement reaction (element + compound). If the Reaction occur it cause rise in temperature, the more the temperature rise, the more active is the metal. Example for compound to use in displacement reactions. Copper Sulphate, Silver Nitrate, or Acids. Reactivity of metals compared with water Cold water + Active metal (from k till Mg)= Metal Hydroxide + Hydrogen Steam + Moderate reactive metals( from Mg till pb) = Metal oxide + Hydrogen Water or Steam + Weak Metal( from copper) = No reaction DR. Anne Mahdy 11  Extraction of metals K Extracted by electrolysis Na Li of their molten source because they are Ba more active than carbon Ca Mg Al C Zn Extracted by the reduction Fe of their sources. Sn Pb H+ Cu Ag Au Pt Extraction means to get the metal free form its compound. Example: A2O3 to get Al free. 1) Aluminum extraction: Aluminum ore is bauxite (Al2O3) It is extracted by electrolysis and not blast furnace (by reduction) as Al is more active than carbon can not reduced by carbon. Al2O3 has very high melting point so it is hard to melt so we mix cryolite because 1) It lower melting point of bauxite so it save time and operating energy 2) perfect solvent for bauxite 3)secondry ore for Al Ex.: Cathode:Al+3+ 3e- →AI Anode :2O-2→ O2 + 4e- become Thinner O2 produced react with graphite anode give CO2 so it is consumed so it should be replaced. It is expensive process bec we use electrical energy DR. Anne Mahdy 12  Extraction of Iron DR. Anne Mahdy Raw materials: 1 - Coke to produce reducing agent and source of energy. 2- Iron ore. Fe2O3 Hematite (main source) Fe3O4 Magnetite 3- hot air 4- Lime stone (CaCO3) to purify iron from sand 5- Water as cooling agent. Extraction by reduction in which Carbon monoxide (reducing agent)produced inside the furnace reduces (remove oxygen from) the iron (III) Oxide to free iron Blast Furnace 11 Making steel. 1-First unwanted impurities are removed from the iron produced in blast furnace The molten iron from blast furnace is purified by blowing oxygen Oxygen react with carbon and sulfur to give carbon dioxide and sulfur dioxide that escape out Then mix iron with carbon to form steel (which is an alloy) Alloy is a mixture of metals or metal with one or more elements usually carbon Alloys are of better properties than metals , they are harder as alloy contains atoms of different sizes which distort the regular layer arrangement of atoms make it difficult for layers to slide over each other TYPES OF STEEL a-LOW carbon steel(mild steel): iron alloy contains 0.25% carbon, easily shaped used to make car body and panel b-High carbon steel: iron alloy with up to 2.5% carbon, hard used in cutting tools C- Stainless steel: iron alloy with chromium and nickel, it resist corrosion used in making cutlery and sinks Uses of iron 1-Railway tracks, bec. Iron is very strong 2- car bodies ,as iron easily shaped and strong Uses of copper 1- electric wiring as it perfect conductor of electricity and ductile 2- saucepans and saucepan bases as it is malleable conduct heat well unreactive 12  Rusting of iron When iron rust is changed to hydrated iron(III)Oxide iron + oxygen + water = hydrated iron(III)oxide 4Fe +3O2+H2O = 2Fe2O3.2H2O 2 main substances both should be presents 1) Oxygen 2) Water. Acids and salts accelerate the rate of rusting * How to prevent rusting: You should keep out oxygen(air) and water by Barrier methods : 1- Painting. : with steel bridges and railing 2- Oiling and greasing : tools and machine parts are coated with a layer of grease or oil 3- sacrificial protection is to cover iron with more active metal : a-for food tins steel is coated with tin by electroplating b-Galvanizing covering iron by Zn layer as it is more active than iron will react with water and oxygen instead of iron to protect it. DR. Anne Mahdy 13  Acid and Base Acids are proton donors in aqueous medium. they are sour, colourless corrosive solutions. Acids are two types: 1- Strong acids completely ionized Large number of ions Good conductor of electricity PH 1-3 2- weak acids (contains carbon or SO3) Partially ionized low number of ions Bad conductor of electricity PH 4-6 Reaction of acids Acid + base(alkali) = salt + water Acid + metal carbonate = salt + water + carbon dioxide Acid + active metal = salt + hydrogen Base Base is a proton acceptor in aqueous medium, all alkalis and bases are weak except group I hydroxide and oxide. Neutralization is a reaction between acid which is proton (H+) donor, and alkali which is a proton acceptor. Indicators: are substances which change its color according to the PH-of the solution. Acid Neutral Bases Red Purple Litmus Solution Blue Phenol Phethaline colourless colourless Pink Methyl Orange V Red - Orange Yellow Strong acid: Strong: Dark Red Green Violet Universal Indicator V Weak acid: VV V- - Weak: yellow or orange Blue - 14  Salt preparation Titration To prepare salts of group I and ammonium It is a reaction between acid and alkali to give salt and water. Ex.How to prepare a sample of sodium chloride crystals from NaOH + HCl Steps: 1- In a conical flask put 25 cm of NaOH using a pipette, add 2 drops of methyl orange, it turns yellow (avoid using universally indicator as it has wide range of colours has no sharp end points) 2- Using a burette titrate HCl till the first orange colour (Neutral point) 3- Record the volume of acid used 4- Repeat without indicator 5- Heat till the point of crystallization, as crystals start to appear on the wall of the test tube leave to cool, filter, wash with few drops of water, dry between two filter papers. DON’T USE UNIVERSAL INDICATOR DURING TITRATION AS IT HAS WIDE RANGE OF COLOUR SHOW NO SHARP END POINT Dissolving To prepare soluble salts other than group I and ammonium Ex. How to prepare a sample of copper sulphate from sulphuric acid and copper (II) oxide. Steps: 1- In a beaker, add 25cm of acid using pipette. 2- Add solid CuO in portion wise till excess (no more dissolve) 3- Filter the mixture using filter funnel and filter paper to remove excess (residue) 4- Heat till the point of crystallization, as crystals start to appear on the wall of the test tube leave to cool, filter, wash with few drops of water, dry between two filter papers. DR. Anne Mahdy 15 Precipitation (Double decomposition) | To prepare insoluble salt in three (3) aqueous solutions. Ex. Prepare a sample of PbCl2. To get the name of the reactant put NO3 after the metal and group one before the non metal. Pb(NO3)2(aq) + 2NaCl(aq)PbCl2(s) + 2NaNO3(aq) Steps: 1- In a beaker add PbNO3 and NaCl 2- Solid (PbCl2) is formed. 3- Filter the mixture by a filter paper and funnel. 4- Get the residue (PbCl2). 5- Wash. 6- Dry between 2 filter papers. TAP FUNNEL Burette. pipette DR. Anne Mahdy 16  Calculation DR. Anne Mahdy Mole calculation rules 1) Moles = Mass (g). Mr 2)Mole = concentration (Mol dm-3 ) x volume (dm3 or cm3/1000) 3)Moles = VOLUME constant (RTP OR 1MOLE OF GAS OCCUPIES 24 ) 4)1mole= 6x10 Steps: given, rule, equation ratio, rule Empirical and molecular formula Empirical formula:is a chemical formula gives the simplest whole number Ratio of different elements present in a compound. Molecular formula = n x empirical formula ex C6H12O6 = 6 (CH2O) Emperical formula EX: 80% C and 20% Hydrogen its relative formula mass = 45 find empirical formula and molecular formula C : H 80 20. 12 1 6.6667 20 divide by smallest mole 6.6667 6.6667 1 3 (final answer should be whole NO. IF 0.5X2 and 0.33 x3 or 0.25 x 4 or normal approximation) so Emperial formula CH3 17 Molecular formula; We have to find n (enlargement factor) n= mass no of molecular formula(given) mass no of empirical formula(we have to calculated) n= 45/15(12+ 3x1) = 3 so molecular formula is 3 times empirical formula C3H9 Percentage yield = (actual amount/theoretical amount)x100 Percentage of an atom in a compound = (mass no. of this atom/mass no of total compound)x100 18  Energy A- During an Exothermic reaction The amount of energy released during bond formation is more than the amount energy absorbed during bond break. B- During an Endothermic reaction: The amount of energy absorbed during bond breaking is more than The amount of energy released during bond formation A-Examples For Exothermic 1-Neutralisation reaction between an acid and an alkali. 2-Displacement reaction. 3-Combustion of a fuel. 4-Dissolving sodium hydroxide in water and reaction of group1 with water 19 20