AQA GCSE CHEMISTRY 8462/1H HIGHER TIER PAPER 1 MERGED QUESTION PAPER & MARKING SCHEME COMBINED 300+ QUESTIONS AND ANSWERS 100%VERIFIED GRADED A+

AQA GCSE CHEMISTRY 8462/1H HIGHER TIER PAPER 1 MERGED QUESTION PAPER & MARKING SCHEME COMBINED 300+ QUESTIONS AND ANSWERS 100%VERIFIED GRADED A+ 1. How do you measure the rate of a reaction? - ANSWER By measuring the quantity of a reactant used or the quantity of product formed over time 2. What is the equation for calculating the mean rate of a reaction by measuring the amount of reactant used? - ANSWER Mean rate of reaction = quantity of reactant used/time taken 3. What is the equation for calculating the mean rate of a reaction by measuring the amount of product formed? - ANSWER Mean rate of reaction = quantity of product formed/time taken 4. What units can you measure the rate of a reaction in? - ANSWER g/s or cm3/s or mol/s 5. How do you calculate the rate of a reaction at a specific time from graph of the quantity of reactant used or the quantity of product formed? - ANSWER By measuring the gradient of a tangent drawn at that specific time on the graph 6. What are the five factors that can affect the rate of a reaction? - ANSWER Concentration of reactants in solution, pressure of reacting gases, surface area of solid reactants, temperature and the presence of a catalyst 7. What theory can we use to explain how various factors affect the rate of a reaction? - ANSWER Collision theory 8. What is collision theory? - ANSWER Chemical reactions can occur only when reacting particles collide with each other and with sufficient energy 9. What is the activation energy of a reaction? - ANSWER The minimum amount of energy that particles must have to react 10. According to collision theory why does increasing concentration of reactant in solution increase the rate of the reaction? - ANSWER It increases the frequency of collisions and so increases the rate of reaction 11. According to collision theory why does increasing the pressure of reacting gases increase the rate of the reaction? - ANSWER It increases the frequency of collisions and so increases the rate of reaction 12. According to collision theory why does increasing the surface area of solid reactants in solution increase the rate of the reaction? - ANSWER It increases the frequency of collisions and so increases the rate of reaction 13. According to collision theory why does increasing temperature increase the rate of the reaction? - ANSWER It increases the frequency of collisions and makes the collision more energetic and so increases the rate of reaction 14. How do you increase the surface area of a solid reactant? - ANSWER Grind it into a powder that has smaller particle size 15. What effect does increasing the temperature of a reaction by 10°C have on the rate of a reaction? - ANSWER It doubles it 16. What is a catalyst? - ANSWER A chemical that changes the rate of a chemical reaction but is not used up in the reaction 17. How do catalysts increase the rate of a reaction? - ANSWER By providing a different pathway for the reaction that has a lower activation energy 18. How do you know in a reaction that a chemical is used in a reaction is a catalyst? - ANSWER It is not included in the chemical equation for the reaction 19. What is a reversible reaction? - ANSWER Where the products of a chemical reaction can react to produce the original reactants 20. What is the symbol used in reversible reaction equations that shows that the reaction is reversible? - ANSWER 21. How can you change the direction of a reversible reaction? - ANSWER By changing the conditions; for example heating or cooling the reaction 22. Describe the energy changes in a reversible reaction - ANSWER One direction will be exothermic and the other direction endothermic 23. When is equilibrium in a reversible reaction achieved in apparatus which prevents the escape of reactants and products? - ANSWER When the rate of the forward and reverse reactions occur at exactly the same rate 24. What affects the relative amount of all the reactants and products at equilibrium in a reversible reaction? - ANSWER The conditions 25. What happens to an equilibrium if any of the conditions change? - ANSWER The system responds to counteract the change 26. What does Le Chatelier's principle predict? - ANSWER The effects of changing conditions on a system at equilibrium 27. What affect will changing the concentration of one of the reactants in a reversible reaction have on the equilibrium? - ANSWER The system will no longer be in equilibrium and the concentration of all the substances will change until equilibrium is reached again 28. What happens when the concentration of a reactant is increased in a reversible reaction? - ANSWER More products will be formed until equilibrium is reached again 29. What happens when the concentration of a product is decreased in a reversible reaction? - ANSWER More reactant will react until equilibrium is reached again 30. What happens when the temperature of a system in equilibrium is increased? - ANSWER The relative amount of products at equilibrium increases for an endothermic reaction OR The relative amount of products at equilibrium decreases for an exothermic reaction What happens when the temperature of a system in equilibrium is decreased? - ANSWER The relative amount of products at equilibrium decreases for an endothermic reaction OR The relative amount of products at equilibrium increases for an exothermic reaction What happens in gaseous reactions when the pressure of a system in equilibrium is increased? - ANSWER The equilibrium position shifts towards the side with the smaller number of molecules as shown by the symbol equation for the reaction What happens in gaseous reactions when the pressure of a system in equilibrium is decreased? - ANSWER The equilibrium position shifts towards the side with the larger number of molecules as shown by the symbol equation for the reaction Where is crude oil found? - ANSWER In rocks What is crude oil formed from? - ANSWER The remains of an ancient biomass consisting mainly of plankton that was buried in mud What chemically is crude oil? - ANSWER A mixture of a large number of compounds; mainly hydrocarbons What is a hydrocarbon? - ANSWER A molecule made up of carbon and hydrogen only What type of hydrocarbons are most of those found in crude oil? - ANSWER Alkanes What is the general formula of alkanes? - ANSWER CnH2n + 2 What are the first four members of the homologous series of alkanes called? - ANSWER Methane, ethane, propane and butane What is a homologous series? - ANSWER A family of organic compounds that have the same functional group, similar chemical properties and the same general formula How can you separate crude oil into fractions? - ANSWER By fractional distillation What does each fraction of crude oil contain? - ANSWER Molecules with a similar number of carbon atoms What can we use each fraction of crude oil for? - ANSWER As fuels or feedstocks for the petrochemical industry Name five fuels produced from crude oil - ANSWER Petrol, diesel, kerosene, heavy fuel oil and liquified petroleum gases Name four useful materials produced by the petrochemical industry from crude oil fractions - ANSWER Solvents, lubricants, polymers and detergents Why are there such a vast range of natural and synthetic carbon compounds? - ANSWER Because of carbon atoms' ability to form families of compounds Describe the four steps involved in fractional distillation - ANSWER Crude oil is heated to evaporate it and turn it into a vapour, the vapour rises through the column and cools, the vapours condense when they are cool enough, and liquids are removed from the column at different heights What three properties of hydrocarbon change as the size of the molecule increase? - ANSWER Boiling point, viscosity and flammability How does the boiling point of a hydrocarbon change as its size increases? - ANSWER It increases How does the viscosity of a hydrocarbon change as its size increases? - ANSWER It increases How does the flammability of a hydrocarbon change as its size increases? - ANSWER It decreases Why are hydrocarbons good fuels? - ANSWER Because during their combustion they release energy What happens to the carbon and hydrogen in a hydrocarbon during combustion? - ANSWER They are oxidised What are the products of complete combustion of a hydrocarbon? - ANSWER Carbon dioxide and water What is the name of the process where hydrocarbons are broken down to produce smaller more useful molecules? - ANSWER Cracking Name the two types of cracking - ANSWER Catalytic cracking and steam cracking What are the conditions for catalytic cracking? - ANSWER 550°C using a zeolite catalyst containing aluminium oxide and silicon oxide What are the conditions for steam cracking? - ANSWER 550°C and steam What is always produced when an alkane undergoes cracking? - ANSWER Smaller alkane molecule(s) and an alkene Which is more reactive, an alkene or an alkane? - ANSWER An alkene How can you test for an alkene? - ANSWER React it with bromine water What do you observe when bromine water is mixed with an alkane? - ANSWER There is no colour change; the bromine water remains orange/brown What do you observe when bromine water is mixed with an alkene? - ANSWER There is a colour change; the bromine water turns colourless Why are alkanes cracked? - ANSWER Because there is a high demand for fuels and some of the products of cracking are useful as fuels What are alkenes used for? - ANSWER To produce polymers and as starting materials to produce other chemicals What are alkenes? - ANSWER Hydrocarbons with a double carbon-carbon bond What is the general formula of an alkene? - ANSWER CnH2n What do saturated hydrocarbons only contain? - ANSWER Single bonds Why are alkenes unsaturated hydrocarbons? - ANSWER Because they contain two fewer hydrogen atoms that the alkane with the same number of carbon atoms What are the names of the first four members of the homologous series of alkenes? - ANSWER Ethene, propene, butene, pentene What is the functional group in alkenes? - ANSWER C=C What determines the reactions of organic compounds? - ANSWER The reactions of the functional group How do alkenes react with oxygen? - ANSWER They undergo incomplete combustion, burning in air typically with a smoky flame How do alkenes react with hydrogen, water and the halogens? - ANSWER By the addition of atoms across the carbon-carbon double bond so that the double bond becomes a single carbon-carbon bond What conditions are required for alkenes to react with hydrogen? - ANSWER Hydrogenation requires a catalyst What conditions are required for alkenes to react with water? - ANSWER Hydration requires the use of steam at 300°C and a catalyst What conditions are required for alkenes to react with halogens? - ANSWER None; the reaction is spontaneous What is the functional group in alcohols? - ANSWER -OH What are the names of the first four members of the homologous series of alcohols? - ANSWER Methanol, ethanol, propanol and butanol What happens when ethanol reacts with sodium? - ANSWER Bubbles of hydrogen gas are seen and sodium ethoxide is produced - ANSWER C2H5OH + Na → H2 + C2H5ONa What happens when alcohols burn in air? - ANSWER They undergo complete combustion to form carbon dioxide and water What happens when alcohols are added to water? - ANSWER They dissolve; though solubility decreases as the molecules increases in size, so butanol is less soluble What happens when alcohols react with an oxidising agent? - ANSWER They are oxidised to carboxylic acids How are aqueous solutions of ethanol produced? - ANSWER By fermentation of sugar solutions using yeast What is the word equation for the fermentation of sugar solution using yeast? - ANSWER Glucose à Ethanol + Carbon Dioxide What are the conditions for fermentation of sugar solution to produce ethanol? - ANSWER Anaerobic conditions (absence of oxygen), 25-35°C What is the functional group in carboxylic acids? - ANSWER -COOH What are the names of the first four members of the homologous series of carboxylic acids? - ANSWER Methanoic acid, ethanoic acid, propanoic acid, butanoic acid What happens when carboxylic acids react with metal carbonates? - ANSWER React to form a salt, carbon dioxide and water What happens when carboxylic acids are added to water? - ANSWER They dissolve to form acidic solutions What happens when carboxylic acids react with alcohols? - ANSWER They form esters Why are carboxylic acids weak rather than strong acids? - ANSWER Carboxylic acids only partially ionise so do not contain as many hydrogen ions as strong acids (which fully ionise) so the pH is higher What is the name of ester formed from ethanoic acid and ethanol? - ANSWER Ethyl ethanoate What are esters used for? - ANSWER Solvents or because they have fruity smells What is the word equation for the formation of esters? - ANSWER Carboxylic acid + alcohol → ester + water What is the name of the reaction that turns alkene into polymers? - ANSWER Addition polymerisation What happens in an addition polymerisation reaction? - ANSWER Many small molecules (monomers) join together to form large molecules (polymers) What is a repeating unit? - ANSWER A part of a polymer that would make a complete polymer molecule if many of them were joined end to end What is the name of the polymer made from propene? - ANSWER Poly(propene) What is condensation polymerisation? - ANSWER Where monomers with two functional groups join together, usually losing small molecules such as water (which is why they are called condensation reactions) What are amino acids? - ANSWER Organic molecules that have two different functional groups (-COOH and -NH2) in the molecule What are formed when amino acids react by condensation polymerisation? - ANSWER Polypeptides What is formed when different amino acids are formed into polypeptides? - ANSWER Proteins What is DNA? - ANSWER Deoxyribonucleic acid is a large molecule essential for life What is the function of DNA? - ANSWER It encodes genetic instructions for the development and functioning of living organisms and viruses Describe the structure of DNA - ANSWER Two polymer chains made form four different monomers called nucleotides, in the form of a double helix what is graphene - ANSWER single layer of graphite, hexagonal lattice, strong covalent bonds between carbon atoms. very strong and light due to covalent bonding excellent electrical conductor(delocalised electrons move freely). Good thermal conductor. Transparent yet impermeable to most substances. useful in electronics and composites. what are fullerenes - ANSWER molecules of carbon atoms with hollow shapes. The structure of fullerenes is based on hexagonal rings of carbon atoms but they may also contain rings with five or seven carbon atoms. first fullerene to be discovered was the buckminster fullerene. what are carbon nanotubes - ANSWER cylindrical fullerenes with very high length to diameter ratios. their properties make them useful for nanotechnology, electronics and materials uses of fullerenes - ANSWER drug delivery - hollow cages lubricants catalysts - large SA used in superconductors carbon nanotubes: very strong conduct electricity - used in tiny circuits conduct heat - used in thermal management systems. what does nanoscience refer to - ANSWER structures that are 1-100 nm in size, of the order of a few hundred atoms. Problems with Nanoparticles - ANSWER 1) Not yet clear whether the nanoparticles can get into your body, and if they do, whether they damage cells or not 2) Possible that when they are washed away, they might damage the environment Simple Molecular Structures - ANSWER Very strong covalent bonds Very weak intermolecular forces Most are liquids & gases at room temperature The bigger the molecule, the stronger the intermolecular forces Don't conduct electricity - no delocalised electrons or ions as they're not charged Why is Buckminsterfullerene a good lubricant? - ANSWER It's shaped like a hollow ball, thus it can roll What is the relative formula mass? - ANSWER The relative atomic masses of all the atoms in the molecular formula added together Formula for Percentage Mass - ANSWER Percentage Mass of an Element in a Compound = Relative Atomic Mass (Ar) x Number of atoms of that element / Relative Formula Mass (Mr) of the compound x 100 What is one mole? - ANSWER An amount of that a substance that contains an Avogadro number of particles What is the Avogadro constant? - ANSWER 6.02x10²³ What is the mass of one mole of atoms of a substance equal to? - ANSWER The relative formula mass of that substance Equation for Number of Moles - ANSWER Number of moles (mol) = Mass (g) of an element/compound / Mr of the element/compound Why is the mass conserved during a chemical reaction? - ANSWER No atoms are created and no atoms are destroyed Change of Mass - Increase - ANSWER If the mass increases, it's probably because one of the reactants is a gas that's found in the air (e.g. oxygen) and all the products are solids, liquids or aqueous Before the reaction, the gas is floating around in the air - it's there, but it's not contained in the reaction vessel, so you can't account for its mass When the gas reacts to form part of the product, it becomes contained inside the reaction vessel - so the total mass of the stuff inside the reaction vessel increases Change of Mass - Decrease - ANSWER If the mass decreases, it's probably because one of the products is a gas and all the reactants are solids, liquids or aqueous Before the reaction, all the reactants are contained in the reaction vessel If the vessel isn't enclosed, then the gas can escape from the reaction vessel as it's formed It's no longer contained in the reaction vessel, so you can't account for its mass - the total mass of the stuff inside the reaction vessel decreases Empirical Formula - ANSWER 1) Divide the mass of each substance by its relative formula mass to find the number of moles 2) Divide the number of moles of each substance by the smallest number of moles in the reaction 3) If any of the numbers aren't whole numbers, multiply all the numbers by the same amount so that they all become whole numbers 4) Write the balanced symbol equation for the reaction by putting these numbers in front of the chemical formula When is a reactant limiting? - ANSWER When it's completed used up in a reaction before the rest and causes the reaction to stop Why are reactants added in excess? - ANSWER To ensure that the limiting reactant is used up What is the amount of product directly proportional to? - ANSWER The amount of limiting reactant What happens when you add more reactant? - ANSWER There will be more reactant particles to take part in the reaction, therefore more product particles Mass of a Product - Calculation - ANSWER 1) Write out the balanced equation 2) Work out relative formula masses of the reactant and the product you want 3) Find out how many moles there are of the substance you know the mass of 4) Use the balanced equation to work out how many moles there'll be of the other substance - that's how many moles of product will be made of this many moles of reactant 5) Use the number of moles to calculate the mass What happens at the same temperature & pressure? - ANSWER Equal numbers of moles of any gas will occupy the same volume What happens at room temperature & pressure? - ANSWER One mole of any gas occupies 24dm³ Equation for Volume of Gas - ANSWER Volume of gas (dm³) = Mass of gas (g)/Mr of gas x 24 What is concentration? - ANSWER The amount of a substance in a certain volume of a solution The more solute there is in a given volume... - ANSWER ...The more concentrated the solution Equation for Concentration (g/dm³) - ANSWER Concentration (g/dm³) = Mass of solute (g) / Volume of solvent (dm³) Equation for Concentration (mol/dm³) - ANSWER Concentration (mol/dm³) = Number of moles of solute (mol) / Volume of solvent (dm³) What are titrations? - ANSWER Experiments that allow you to find the volumes needed for two solutions to react together completely How do you convert mol/dm³ to g/dm³? - ANSWER Find the concentration in mol/dm³ then convert the concentration using the equation: mass = moles x Mr What is atom economy? - ANSWER The atom economy (atom utilisation) of a reaction tells you how much of the mass of the reactants is wasted when manufacturing a chemical and how much ends up as useful products Equation for Atom Economy - ANSWER Atom economy = Relative formula mass of desired products / Relative formula mass of all reactants x 100 What does 100% atom economy mean? - ANSWER All the atoms in the reactants have been turned into useful (desired) products - the higher the atom economy, the 'greener' the process Why is a low atom economy bad? - ANSWER 1) The reactions use up resources very quickly 2) They make a lot of waste materials that have to be disposed of 3) The reactions are unsustainable - the raw materials will run out & the waste has to go somewhere 4) Reactions aren't usually profitable 5) Raw materials are expensive to buy 6) Waste products can be expensive to remove and dispose of responsibly How do you fix the problem of a low atom economy reaction? - ANSWER Find a use for the waste products - come up with a reaction that gives useful 'by-products' rather than useless ones How many products do the highest atom economy reactions have? - ANSWER Only one product - the lower the number of products, the higher the atomy economy is likely to be What is the yield? - ANSWER The amount of product you get - the more reactants there are, the higher the yield will be Equation for Percentage Yield - ANSWER Percentage Yield = mass of product actually made (g) / Maximum theoretical mass of product (g) x 100 Why do industrial processes need a high percentage yield? - ANSWER It reduces waste and costs In real life, do you ever get a 100% yield? - ANSWER No - some product or reactant always gets lost along the way Problems of getting a 100% yield - Problem 1 - ANSWER Not all reactants react to make a product - in reversible reactions, the products can turn back into reactants, so the yield will never be 100% Problems of getting a 100% yield - Problem 2 - ANSWER There might be side reactions - the reactants sometimes react differently to how you expect They might react with gases in the air, or impurities in the reaction mixture, which forms extra products other than the ones you want Problems of getting a 100% yield - Problem 3 - ANSWER When you filter a liquid to remove solid particles, you nearly always lose a bit of liquid or a bit of solid If you want to keep the liquid, you'll lose the bit that remains with the solid and filter paper If you want to keep the solid, some of it'll get left behind when you scrape it off the filter paper You'll always lose a bit of material when you transfer it from one container to another - some always gets left behind on the inside surface of the old container What neutralises an acid? - ANSWER A base (alkali) Neutralisation equation - ANSWER Acid + base -- salt + water What do acids form in water? - ANSWER Positive hydrogen ions What do alkalis form in water? - ANSWER Negative hydroxide ions Symbol equation of neutralisation - ANSWER H(positive) + OH(negative) -- H2O What do strong acids do in water? - ANSWER They ionise completely - all acid particles dissociate to release positive hydrogen ions What do weak acids do in solution? - ANSWER They don't fully ionise in solution - only a small proportion of acid particles dissociate to release positive hydrogen ions Examples of strong acids - ANSWER Sulfuric acid Hydrochloric acid Nitric acid Examples of weak acids - ANSWER Ethanoic acid Citric acid Carbonic acid How do acids react? - ANSWER The positive hydrogen ions react with other substances What happens if the concentration of positive hydrogen ions is higher? - ANSWER The rate of reaction will be faster, therefore strong acids will be more reactive than weak acids of the same concentration What is pH? - ANSWER A measure of the concentration of positive hydrogen ions in the solution For every decrease of 1 on the pH scale... - ANSWER ...The concentration of positive hydrogen ions increase by a factor of 10 - Logarithmic E.g. pH 4 has 10 times the concentration of pH 5 What does acid strength tell you? - ANSWER What proportion of the acid molecules ionise in water Are metal oxides and hydroxides bases or acids? - ANSWER Bases Are metal carbonates bases or acids? - ANSWER Bases Equation with a metal carbonate - ANSWER Acid + metal carbonate -- salt + water + carbon dioxide Reactivity series - ANSWER Potassium Sodium Lithium Calcium Magnesium Aluminium CARBON Zinc Iron Tin Lead HYDROGEN Copper Silver Gold Platinum Metals that react with water out of the RS - ANSWER Potassium, sodium, lithium and calcium Metals that don't react with water out of the RS - ANSWER Zinc, iron and copper Oxidation = - ANSWER Gain of oxygen Loss of electrons Reduction = - ANSWER Loss of oxygen Gain of electrons Metals higher than carbon... - ANSWER ...Have to be extracted by electrolysis Metals lower than carbon... - ANSWER ...Have to be extracted by carbon reduction What are redox reactions? - ANSWER REDuction and OXidation happen at the same time (REDOX) What is electrolysis? - ANSWER The process by which ionic substances are broken down into simple substances using electricity What happens during electrolysis? - ANSWER An electric current is passed through an electrolyte which causes the ions to move towards the electrodes where they react and the compound decomposes Cathode - ANSWER Negative electrode Positive ions move towards it Electrons are gained Reduction happens Anode - ANSWER Positive electrode Negative ions move towards it Electrons are lost Oxidation happens Can an ionic solid be electrolysed? - ANSWER No, because the ions are in fixed positions and can't move Can a molten ionic compound be electrolysed? - ANSWER Yes, because the ions can move freely and conduct electricity Aluminium Oxide - Cathode Half Equation - ANSWER Al(three plus) + 3e(minus) -- Al Aluminium Oxide - Anode Half Equation - ANSWER 2O(two minus) -- O2 + 4e(minus) Cathode - If the element is more reactive than hydrogen... - ANSWER ...Hydrogen gas will be produced Anode - If there are no halogen ions (halide ions)... - ANSWER ...Oxygen will be produced Cathode - If the element is less reactive than hydrogen... - ANSWER ...The element will be released from the cathode Anode - If there are halogen ions (halide ions)... - ANSWER ...They will be released from the anode Hydrogen Half Equation - ANSWER 2H(plus) + 2e(minus) -- H2 Chlorine Half Equation - ANSWER 2Cl(minus) -- Cl2 + 2e(minus) What is an ore? - ANSWER A rock which contains a metal that's worth extracting - there's enough of the metal in it to make it economic to extract What are the most common ores? - ANSWER Oxides and sulfides What is a negative ion? - ANSWER Anion What is a positive ion? - ANSWER Cation Method on making salt crystals - Evaporation - ANSWER 1) Put goggles on and tie hair back. Pour sulfuric acid into a beaker 2) Using a bunsen burner, heatproof mat, tripod and gauze, heat the acid until it just starts to boil 3) Off the heat, stir some copper oxide into the acid using a stirring rod. 4) Continue to add a little bit more after each addition has dissolved until there is excess copper oxide at the bottom of the beaker and the acid has turned blue 5) Put filter paper into a filter then put that into a conical flask - filter the solution into the conical flask 6) Once filtered, pour the solution into a petri dish and leave alone overnight until salt crystals have formed Safety Precautions on Crystals Experiment - ANSWER 1) If during the experiment you spill acid on your hands, wash it off immediately 2) If you break a glass beaker, ensure everyone knows where the glass is and carefully sweep it up with a dustpan and brush 3) Ensure all long hair is tied up to prevent spilling acid on it What are titrations used for? - ANSWER Finding out exactly how much acid is needed to neutralise a quantity of alkali - or vice versa Titration Method - ANSWER 1) Rinse out the burette & pipette using distilled water - ensure every last drop is thoroughly out 2) Write the acid on one beaker and the alkali on the other. Pour the acid & alkali into their beakers 3) Fix the metal rod into the clamp stand and attach the clamp holder. Slip the burette firmly inside the holder and place the stand on a surface where the top of the burette is at eye level or below. Place a ceramic square under the burette and a plastic pot on that. Put a funnel in the burette 4) Pour 50cm³ of the acid into the burette & overshoot by 1-2cm³. Let the excess acid run out into the pot. Remove the funnel & use the laminated piece of paper to ensure the volume of acid is exactly 50cm³ 5) Use the pipette filler to fill the pipette with 50cm³ of alkali. Add it to the conical flask with some indicator. The alkali should turn pink 6) Carefully, add the acid to the alkali, swirling the conical flask to mix the solutions. As soon as the hydroxide turns colourless, stop adding the acid. Use the laminated piece of paper to identify the volume of acid added 7) Record your results and repeat the experiment 4 more times, or until you find 2-3 results that are within 0.2cm³ of each other. Calculate an average 8) Repeat the experiment with the average but omit the indicator Litmus indicator - ANSWER Acid = red Alkali = blue Methyl orange - ANSWER Acid = red Alkali = yellow Phenolphthalein - ANSWER Acid = colourless Alkali = pink Reaction of Metal with Water - ANSWER Metal + Water -- Metal Hydroxide + Hydrogen Formation of a metal ore = - ANSWER Oxidation Extraction of a metal = - ANSWER Reduction Making Soluble Salts Using an Insoluble Base - Method - ANSWER 1) Gently warm the dilute acid using a Bunsen burner, then turn off the Bunsen burner 2) Add the insoluble base to the acid a bit at a time, until no more reacts. You'll know when all the acid has been neutralised because even after stirring, the excess solid will just sink to the bottom of the flask 3) Filter out the excess solid to get the salt solution 4) To get pure, solid crystals of the salt, gently heat the solution using a water bath or an electric heater to evaporate some of the water, then stop heating it & leave the solution to cool. Crystals of salt should form which can be filtered out of the solution & then dried What's the difference between a burette and a pipette? - ANSWER 1) A burette measures varying volumes 2) A pipette measures fixed volumes Exothermic reactions - ANSWER Heat energy is given out to the surroundings during a chemical reaction. The temperature increases Endothermic reactions - ANSWER Heat is taken in from the surroundings during a chemical reaction. The temperature decreases Examples of exothermic reactions - ANSWER Combustion Neutralisation Many oxidation reactions Examples of endothermic reactions - ANSWER Thermal decomposition What is the activation energy? - ANSWER The energy needed to start the reaction It is the minimum amount of energy the reactants need to collide with each other and react What do most exothermic reactions involve? - ANSWER Burning fuels Reaction profiles - exothermic - ANSWER Products are at a lower energy than the reactants Reaction profiles - endothermic - ANSWER Products are at a higher energy than the reactants What is bond breaking? - ANSWER Endothermic process - energy is supplied to break existing bonds What is bonding formation? - ANSWER Exothermic process - energy is released when new bonds are formed What is an electrochemical cell? - ANSWER A basic system made up of 2 different electrodes (usually metals, in order to conduct electricity) in contact with an electrolyte What is an electrolyte? - ANSWER A liquid that contains ions which react with electrodes What happens in an electrochemical cell? - ANSWER The chemical reactions between the electrodes & the electrolyte set up a charge difference between the electrodes If the electrodes are connected by a wire, the charge is able to flow & electricity is produced A voltmeter can be connected to the circuit to measure the voltage of the cell What causes the charge difference (voltage) in an electrochemical cell? - ANSWER Different metals react differently with the same electrolyte What affects the voltage of a cell? - ANSWER 1) The type of electrodes used 2) Concentration of the electrolyte 3) Temperature How is a battery formed? - ANSWER By connecting two or more cells together in series - the voltages are combined so there is a bigger voltage overall for the battery Why are some chemical reactions irreversible at the electrodes? - ANSWER Over time, the reacting particles get used up and turned into products of the reaction - once any of the reactants are used up, the reaction can't happen, therefore no electricity is produced If the products can't be turned back into reactants, the cell won't be recharged What are non-rechargeable batteries? - ANSWER Batteries which contain cells which use irreversible reactions - once one of the reactants is used up, they don't produce any more charge, therefore you have to replace them E.g. alkaline batteries How can you reverse a reaction in a rechargeable cell? - ANSWER Connecting the cell to an external electric current What is a fuel cell? - ANSWER An electrical cell that's been supplied with a fuel and oxygen (or air) and uses energy from the reaction between them to produce electrical energy efficiently When the fuel enters the cell, it becomes oxidised and sets up a p.d. within the cell Hydrogen-Oxygen Fuel Cell - ANSWER Combines hydrogen & oxygen to produce nice, clean water and release energy What type of reaction do hydrogen-oxygen fuel cells involve? - ANSWER A redox reaction Process of electrolysis in a hydrogen-oxygen fuel cell - ANSWER 1) Hydrogen goes into the anode compartment and oxygen goes into the cathode compartment 2) At the anode, hydrogen loses electrons to produce H⁺ ions - oxidation 3) At the cathode, oxygen gains electrons from the cathode and reacts with the H⁺ ions to make water - reduction 4) The electrons flow through an external circuit from the anode to the cathode - electric current 5) The overall reaction is hydrogen + oxygen -- water What is the electrolyte for a hydrogen-oxygen fuel cell? - ANSWER A solution of potassium hydroxide What are the electrodes for a hydrogen-oxygen fuel cell? - ANSWER Porous carbon with a catalyst Why will the electrolyte affect the size of the voltage in a cell? - ANSWER The different ions in solution will react differently with the metal electrodes used Why are conventional fuels bad? - ANSWER For vehicles (e.g. petrol), they have a finite supply and they're very polluting Why are hydrogen-oxygen fuel cells better than batteries for cars? - ANSWER 1) Don't produce as many pollutants as other fuels as the only by-products are water & heat - batteries for electric vehicles are polluting to dispose of due to the highly toxic metal compounds they contain 2) Batteries have a limit to the number of times they can be recharged and they're more expensive to make 3) Store less energy than fuel cells - would need to be recharged more often, and recharging takes a long time Testing the effect of acid concentration on the energy released during neutralisation - Method - ANSWER 1) Put 25cm³ of 0.25mol/dm³ of HCl & NaOH in separate beakers 2) Place the beakers in a water bath set to 25°C until they are both at the same temperature 3) Add the HCl followed by the NaOH to a polystyrene cup with a lid 4) Take the temperature of the mixture every 30 seconds & record the highest temperature 5) Repeat steps 1-4 using 0.5mol/dm³ & then 1mol/dm³ of HCl Measuring Energy Transfer - Method - ANSWER 1) Fill a polystyrene cup with the reaction mixture & measure the temperature. Record it in a table 2) Put a lid on the cup then put it in a large beaker. Measure the temperature of the mixture every 30 seconds for 5 minutes 3) Repeat this experiment but with different insulating materials inside the large beaker, wrapped around the cup e.g. cotton wool, newspaper etc 4) Compare the different temperatures for each material to find the best insulator size of nanoparticles - ANSWER smaller than fin particles which have diameters between 100 and 2500nm (1x10-7m and 2.5x10-6m what happens to the surface area to volume ratio of a cube when the side of a cube decreases by a factor of 10 - ANSWER the sa to vol ratio increases by factor of 10 what are the applications of nanoparticles - ANSWER medicine electronics, cosmetics and sun creams, deoderants, catalysts. explain that there are possible risks associated with the use of nanoparticles. - ANSWER Health risks: Nanoparticles are so small they may enter the body through the skin, lungs, or bloodstream, and their effects are not fully understood. Toxicity: Some may be toxic to cells or cause inflammation. Environmental risks: They could accumulate in the environment, harming organisms or ecosystems. Uncertainty: Because nanoparticles behave differently from larger particles, their long term impacts are still unknown. what does the law of conservation of mass state - ANSWER that no atoms are lost or made during a chemical reaction so mass of products = mass of reactants. what is the relative formula mass of a compound - ANSWER the sum of the relative atomic masses of the atoms in the numbers shown in the formula how can some reactants appear to involve a change in mass but dont actually have one - ANSWER because a reactant or product is a gas and hasn't been taken into account for For example: when a metal reacts with oxygen the mass of the oxide produced is greater than the mass of the metal or in thermal decompositions of metal carbonates carbon dioxide is produced and escapes into the atmosphere leaving the metal oxide as the only solid product. how do you calculate uncertainty - ANSWER find range of the results and divide by 2 what is a mole - ANSWER the amount of a substance which contains 6.02x10^23 particles which is avagadro's constant. equation linking mass mr and moles - ANSWER mass = mols x mr equation linking conc mass and vol - ANSWER conc = mass/vol therefore the mass of a solute and the volume of a solution is related to conc of solution. equation linking conc mols and vol - ANSWER conc = mols/vol what is the limiting reactant - ANSWER the reactant in a reaction which is completely used up when reacted with something in excess as it limits the amount of product why is it sometimes not possible to obtain calcuated amount of product - ANSWER reaction may not go to completion as its reversible. some of product may be lost when separated from reaction mixture some of reactants may react in ways different to expected reaction. what is the percentage yield - ANSWER the amount of product obtained compared with the maximum theoretical yield % Yield= Mass of product actually made / Maximum theoretical mass of product ×100 what is the atom economy - ANSWER a measure of the amount of starting materials that end up as useful products Relative formula mass of desired product from equation / Sum of relative formula masses of all reactants from equation ×100 equation to calculate volume of gas at room temp and pressure (dm^3) - ANSWER moles x 24 what are the reactions metals with oxygen called - ANSWER oxidation reactions as the metals gain oxygen. reactivity series - ANSWER Potassium (K) Sodium (Na) Calcium (Ca) Magnesium (Mg) Aluminum (Al) Zinc (Zn) Iron (Fe) Tin (Sn) Lead (Pb) Copper (Cu) Silver (Ag) Gold (Au) Platinum (Pt) explain how the reactivity of metals with water or dilute acids is related to the tendency of the metal to form its positive ion - ANSWER Metals react by losing electrons to form positive ions (cations). The easier it is for a metal atom to lose electrons, the more reactive it is. Highly reactive metals (e.g., sodium, potassium) readily form positive ions → vigorous reactions with water and acids. Less reactive metals (e.g., copper) do not easily lose electrons → little or no reaction. Reactivity trend: linked directly to the tendency of the metal to form positive ions. how are most metals found as - ANSWER compounds that require chemical reactions to extract the metal. how can metals less reactive than oxygen be extracted from their oxides - ANSWER by reduction with carbon how do write ionic equations - ANSWER Write the full balanced equation. Split soluble ionic compounds into ions. Cancel out spectator ions (those unchanged). Example: AgNO3(aq)+NaCl(aq)→AgCl(s)+NaNO3(aq)AgNO3(aq) + NaCl ===AgCl(s) + NaNO3(aq) Ionic form: Ag+(aq)+Cl−(aq)→AgCl(s) what do acids react with some metals to produce - ANSWER salts and hydrogen explain how this is a redox reaction - ANSWER Metal atoms lose electrons → form positive ions (oxidation). Hydrogen ions (H⁺) from the acid gain electrons → form hydrogen gas (reduction). Because oxidation and reduction happen together, the reaction is a redox reaction. what is the general equation for when a metal reacts with an acid - ANSWER Metal + Acid === Salt + Hydrogen equation for neutralisation of acid by alkalis(slouble metal hydroxides) and bases(insoluble metal hydroxides) - ANSWER Acid + Base == salt + water same but with metal carbonates - ANSWER Acid + Metal Carbonate == salt + water + carbon dioxide what does the particular salt produced depend on - ANSWER acid used (hcl produces chlorides etc) the positive ions in the base, alkali or carbonate. how do you make pure dry samples of salt using acid and insoluble base/ metal/ carbonate - ANSWER Add excess solid to the acid until no more reacts. Filter to remove unreacted solid. Heat the solution gently to evaporate some water. Leave to crystallise. Filter crystals and dry with paper. how do you make pure dry samples of salt using acid and alkali (both soluble) - ANSWER Use titration to find exact volumes needed. Mix acid and alkali in correct proportions. Evaporate water from the neutral solution. Leave to crystallise. Filter crystals and dry. what ions do acids produce in aqueous solutions - ANSWER Hydrogen ions, alkali aqueous solution contains hydroxide ions. what is the ph scale - ANSWER a measure of the acidity or alkalinity of a solution, can be measured using universal indicator or pH probe. what happens in a neutralisation reaction between an acid and an alkali - ANSWER h ions react with OH ions to produce water H(aq) + OH-(aq)=== H2O(l) Describe how to carry out titrations using strong acids (HCl, H₂SO₄, HNO₃) and strong alkalis to find reacting volumes accurately. - ANSWER Measure alkali into a conical flask using a pipette (accurate volume). Add indicator (e.g., phenolphthalein or methyl orange). Fill burette with acid (HCl, H₂SO₄, or HNO₃). Run acid in slowly, swirling flask, until indicator changes colour (end point). Record burette reading → gives volume of acid needed. Repeat until concordant results (within 0.1 cm³). Average concordant titres → accurate reacting volume. required practical 2 (titration) - ANSWER what happens to a strong/weak acid in aqueous solution - ANSWER strong = completely ionised weak = partially ionised weak acids are acids such as ethanoic citric and carbonic acids what is trend between ph and hydrogen ion conc. - ANSWER as ph decreases by 1 unit, h ion conc increases by factor of 10 what is acidity/alkalility - ANSWER the compounds ability to dissociate H+ (for acidity) or OH- (for alkalinity) ions in solution what are electrolytes, what must an electrolyte be - ANSWER liquids and solutions that are able to conduct electricity, must be molten or aqueous for the ions to move freely and conduct electricity. what happens in electrolysis - ANSWER cations go to the cathode and anions go to the anode. ions are discharged and elements are formed. how is aluminium produced in electrolysis - ANSWER by electrolysis of molten mixture of aluminium oxide and cryolite using carbon as positive electrode. Explain why the positive electrode must be continually replaced in electrolysis. - ANSWER The positive electrode (anode) is made of carbon (often graphite). During electrolysis, oxygen forms at the anode. Oxygen reacts with the carbon electrode → produces carbon dioxide gas. This reaction causes the electrode to wear away gradually. Therefore, the positive electrode must be continually replaced to keep the process working. what is the rule at the cathode - ANSWER hydrogen is produced if the metal is more reactive than hydrogen. what is the rule at the anode - ANSWER oxygen is produced unless the solution contains halide ions when the halogen is produced. required practical 3 - ANSWER what happens at the cathode/ anode examples of simple half equations - ANSWER positively charged ions gain electrons and so the reactions are reductions. negatively charged ions lose electrons and so the reactions are oxidations. 2H+ + 2e- → H2 and 4OH- → O2 + 2H2 O + 4e- key facts about energy - ANSWER energy is conserved in reactions what is an exothermic reaction, everyday uses - ANSWER a reaction that transfers energy to surrounding so temp of surroundings increase. self-heating cans, hand warmers what is an endothermic reaction - ANSWER takes in energy from urrounding so temp of surroundings decrease. when can chemical reactions only occur - ANSWER when reacting particles collide with each other at sufficient energy what is activation energy - ANSWER the minimum amount of energy that particles need to react. how can a simple cell be made - ANSWER by connecting 2 different metals in contact with an electrolyte. what do batteries consist of - ANSWER two or more cells connected together in series to provide a greater voltage. when does the reaction stop in a non rechargeable cell - ANSWER when one of the reactants has been used up, an example of a non rechargeable battery is an alkaline one. why can rechargeable cells and batteries be recharged. - ANSWER becase the chemical reactions are reversed when an external electrical current is supplied. what are fuel cells supplied by - ANSWER an external source of fuel (like hydrogen) and oxygen or air. what happens - ANSWER the fuel is oxidised electrochemically within the fuel cell to produce a potential difference what does the overall reaction in a hydrogen fuel cell involve - ANSWER the oxidation of hydrogen to produce water What effect does using a catalyst have on the yield of ammonia in the Haber process? - ANSWER None. It just reduces the time for the system to reach equilibrium. What types of compounds are used in artificial fertilisers? - ANSWER Compounds of nitrogen, phosphorus and potassium are used to make NPK fertilisers What are NPK fertilizers? - ANSWER Formulations of various salts containing appropriate percentages of the elements (nitrogen, phosphorus and potassium) Name the salts that are used to provide nitrogen, phosphorus and potassium in fertilisers - ANSWER Ammonium nitrate (NH4NO3), ammonium sulfate ((NH4)2SO4), ammonium phosphate ((NH3)3 PO3),potassium nitrate (KNO3) What is ammonia used to manufacture? - ANSWER Ammonium salts and nitric acid Where are potassium salts obtained from for fertilisers? - ANSWER By mining Where is phosphate rock obtained from for fertilisers? - ANSWER By mining What does phosphate rock have to be treated with before it can be used as a fertiliser? - ANSWER Acid What is produced when phosphate rock is treated with nitric acid? - ANSWER Calcium nitrate and phosphoric acid What is produced when phosphate rock is treated with sulfuric acid? - ANSWER Single superphosphate (a mixture of calcium sulfate and calcium phosphate) What is produced when phosphate rock is treated with phosphoric acid? - ANSWER Triple superphosphate (calcium phosphate) Name three naturally occurring polymers important for life - ANSWER Proteins, starch and cellulose What is the monomer that the naturally occurring polymers starch and cellulose are made from? - ANSWER Glucose What is the scientific definition of a pure substance? - ANSWER A single element or compound not mixed with another substance What are the properties of pure substances? - ANSWER Pure substances melt and boil at specific temperatures; this can be used to identify the pure substance What is an everyday description of a pure substance? - ANSWER A substance that has had nothing added to it, so it is unadulterated and in its natural state (such as milk) What is a formulation? - ANSWER A mixture designed as a useful product How are formulations made? - ANSWER By mixing the components in carefully measured quantities to ensure the product has the required properties Give seven examples of formulations? - ANSWER Fuels, cleaning agents, paints, medicines, alloys, fertilisers and foods What is chromatography used for? - ANSWER To separate mixtures What can the results of chromatography be used for? - ANSWER To identify substances What are the two phases involved in chromatography? - ANSWER Stationary phase, mobile phase What does separation of substances depend upon in chromatography? - ANSWER The distribution of substances between phases What is an alloy? - ANSWER A mixture of two or more elements, one of which is a metal What is bronze? - ANSWER An alloy of copper and tin What is brass? - ANSWER An alloy of copper and zinc What is gold alloyed with for use in jewellery? - ANSWER Silver, copper and zinc How many carats does pure gold have? - ANSWER 24 How many carats does gold jewellery containing 75% gold have? - ANSWER 18 What are steels? - ANSWER Alloys of iron that contain specific amounts of carbon and other metals What are the properties of high carbon steel? - ANSWER Strong but brittle What are the properties of low carbon steel compared to high carbon steel? - ANSWER Softer than high carbon steel but more easily shaped What is stainless steel? - ANSWER Steels containing chromium and nickel that are hard and resistant to corrosion What is the main advantage of aluminium alloys? - ANSWER Aluminium alloys are low density What type of glass is the glass we use most of? - ANSWER Soda-lime glass How is soda-lime glass made? - ANSWER By heating a mixture of sand, sodium carbonate and limestone What is borosilicate glass made from? - ANSWER Sand and boron trioxide What is the advantage of borosilicate glass over soda-lime glass? - ANSWER Borosilicate glass melts at a higher temperature Give two examples of clay ceramics - ANSWER Pottery and bricks How are clay ceramics made? - ANSWER By shaping wet clay and then heating in a furnace What do the properties of polymers depend upon - ANSWER What monomers the polymer is made from and the conditions under which they are made Name the two polymers made from ethene - ANSWER Low density poly(ethene) (LDPE) and high density poly(ethene) (HDPE) How is low density poly(ethene) produced? - ANSWER Under conditions that produce branches in the polymer so the polymers are arranged randomly How is high density poly(ethene) produced? - ANSWER Under conditions which produce less branching so that the polymer chains line up more closely What are themosoftening polymer? - ANSWER Polymers that melt when heated and so can be easily recycled What are thermosetting polymers? - ANSWER Polymers that do not melt when heated as there are crosslinks containing strong covalent bonds between the polymer chains (which are not there in thermosoftening polymers) What is a composite material? - ANSWER A material made up of two materials with different properties What is a composite material made up of? - ANSWER A material made from two components, a matrix or binder surrounding and binding fibres or fragments of the other material, which is called the reinforcement Give four examples of composite materials - ANSWER Reinforced steel (reinforcement:steel, matrix:concrete), Fibreglass (glass fibres, polymer resin), carbon fibre (carbon fibres, polymer resin), chipboard ( wood chips, resin glue) What is the Haber process used to manufacture? - ANSWER Ammonia What is ammonia used to make? - ANSWER Nitrogen-based fertilisers What are the raw materials for the Haber process - ANSWER Nitrogen from the air and hydrogen from natural gas What is the symbol equation for the Haber process? - ANSWER N2 (g) + 3H2 (g) D 2NH3 (g) Describe the Haber process (reversible reaction) - ANSWER Purified gases are passed over a catalyst at 450°C and 200 atmospheres. Some of the hydrogen and nitrogen react to form ammonia which on cooling liquifies and is removed. The remaining hydrogen and nitrogen are recycled. Which conditions would produce the highest yield of ammonia? - ANSWER Low temperature, high pressure Why does a low temperature produce a higher yield of ammonia? - ANSWER The forward reaction is exothermic so a lower temperature moves the equilibrium to the right to increase the temperature making more products Why does a high pressure increase the yield of ammonia? - ANSWER There are fewer molecules on the right hand side of the reaction so the equilibrium will shift to the right to reduce the pressure Why is a temperature of 450°C used in the Haber process? - ANSWER It is a compromised temperature to produce a reasonable yield of ammonia at a suitable rate Why is a pressure of 200 atmosphere used in the Haber process? - ANSWER To increase the yield of ammonia without incurring the very high energy and equipment costs for achieving very high pressures what are compounds, what is the only way they can be separated - ANSWER they contain two or more elements chemically bonded only be separated into elements by chemical reactions. what is a mixture - ANSWER the combination of two or more elements or compound not chemically bonded. how do you form a half equation - ANSWER Write down the reactant and the product. Balance the atoms. Write the total charge underneath each species in the equation. Balance the charge by adding electrons. O2- → O22 2O2- → O2 2O2- → O2 + 4e- how can mixtures be separated - ANSWER filtration, crystallisation, simple distillation, fractional distillation and chromatography. these processes don't involve chemical reactions and no new substances are made. when is filtration, evaporation, used - ANSWER filtration: to separate an insoluble solid from a liquid. evaporation: make crystals. as the solution cools the crystals can be obtained by filtration what is the process of simple distillation, when is it used, apparatus - ANSWER separate a liquid from a solution distillation flask, heat source, thermometer and condenser. - mixture is heated in distillation flask - the vapour travels up neck of flask and into condenser where it cools into liquid form. - the condensed liquid is collected in a separate container and the solid is left behind. paper chromatography - ANSWER used to separate substances that have different solubilities. -pencil line drawn on paper and spots of sample are placed on this line, pencil used as ink would bleed. - The paper is then lowered into the solvent container, making sure that the pencil line sits above the level of the solvent, so the samples don't wash into the solvent container The solvent travels up the paper by capillary action, taking some of the coloured substances with it Different substances have different solubilities so will travel at different rates, causing the substances to spread apart Those substances with higher solubility will travel further than the others This will show the different components of the ink / dye If two or more substances are the same, they will produce identical chromatograms If the substance is a mixture, it will separate on the paper to show all the different components as separate spots An impure substance will show up with more than one spot, a pure substance should only show up with one spot what were atoms thought to be before the discovery of the elctron - ANSWER tiny spheres that couldn't be divided. what is the plum pudding model/ alpha particle scattering experiment - ANSWER discovery of electron led to it. it suggested that the atom is a ball of positive charge with negative electrons embedded in it. what was the alpha particle scattering experiment / results - ANSWER concluded mass of an atom was concentrated at nucleus. this nuclear model which replaced the plum pudding model who suggested the nuclear model, what did they suggest - ANSWER Niels Bohr, suggested electrons orbit nucleus at specific distances. his theoretical calculations agreed with experimental observations. what did later experiments lead to - ANSWER the idea that the positive charge of any nucleus could be subdivided into a whole number of smaller particles, each particle having the same amount of positive charge. The name proton was given to these particles. what did james chadwick's experimental work provide - ANSWER evidence to show existence of neutrons within nucleus about 20 years after the nucleus became an accepted scientific idea. what was the gold foil experiment. what conclusions could be taken from it. who was it by who was plum pudding model by - ANSWER 1909 ernest rutherford. positioned a lead block containing alpha particle emitting source at gold foil. - most passed straight through showing majority of atom is empty space. - some were deflected majorly showing presence of dense positively charged nucleus as positives repel. describe the difference between the plum pudding model of the atom and the nuclear model of the atom. - ANSWER the plum pudding model depicts the atom as a uniform sphere of positive charge with electrons scattered throughout while the nuclear model presents a dense nucleus with electrons orbiting around the nucleus. in an atom what is the number of electrons equal to - ANSWER the number of protons in the nucleus what is an atom's atomic number - ANSWER the number of protons in an atom what is the radius of an atom - ANSWER 0.1nm where is nearly all the mass of an atom - ANSWER in its nucleus. what is the mass number - ANSWER the number of protons and neutrons in an atom. at the top of the number on the periodic table what is an isotope - ANSWER an atom with the same number of protons but a different number of neutrons. what is the relative atomic mass of an element - ANSWER the average mass of an element's atoms compared to 1/12 the mass of a carbon 12 atom, calculated using the abundances of its isotopes. equation = ((mass of isotope a x abundance of a) + ( mass of isotope b x abundance of b))/ 100 what do electrons in an atom occupy (in terms of energy levels.) - ANSWER occupy the lowest available energy levels (innermost available shells) most on first shell = 2 most on rest shells = 8 what are the elements in the periodic table arranged in order of - ANSWER atomic number (amount of protons). arranged so that elements with similar properties are in the same groups. Why is the table called the periodic table? - ANSWER because similar properties occur at regular intervals. how were elements before the discovery of protons neutrons and electrons classified as - ANSWER by arranging them in order of their atomic weights. how did mendeleev overcome some of the problems with the early periodic tables - ANSWER he left gaps for elements he thought hadn't been discovered and in some places changed the order based on atomic weights what did knowledge of isotopes make possible to explain with the early periodic table - ANSWER why the order based on atomic weights was not always correct. what ions do metals react to form, therefore what do non metals form - ANSWER positive ions. non metals = not positive ions. where are metals found in the periodic table, where are non metals found - ANSWER metals = to the left and the bottom non metals = right and top. explain the differences between metals and non-metals on the basis of their characteristic physical properties luster state at room temp conductivity melting and boiling points malleability and ductility. - ANSWER *luster* metals = shiny and lustrous, reflect light non = generally dull and non lustrous *state at room temp* metals = mostly solid except mercury - liquid non = can be solid like carbon liquid like bromine or gas like oxygen *malleability and ductility* metals = malleable (can be hammered into thin sheets) and ductile (can be drawn into wires) non = brittle when solid, shatter/ break when force applied. *conductivity* metals = excellent conductors of heat and electricity due to delocalised sea of electrons. non = poor conductors of heat and electricity , most are insulators. *melting and boiling points* metals = have high melting and boiling points non = have lower melting and boiling points explain the differences between metals and non-metals on the basis of their characteristic chemical properties. reactivity electronegativity and ionisation energy. - ANSWER *Reactivity* metals = tend to lose electrons during chemical reactions, forming cations. react with acids to produce hydrogen and basic oxides. like magnesium oxide non = tend to gain electrons form anions. usually don't react with acids and form acidic or neutral oxides like co2 *electronegativity and ionisation energy* metals = low electronegativity and ionisation energy, makes it easier to lose electrons. non = high electonagetivity and ionisation power makes it easier for them to gain electrons. what are elements in group 0 called - ANSWER the noble gasses what is the reactivity of group 0 - ANSWER they are unreactive and don't form molecules easily because their atoms have stable arrangements of electrons. what only element in the noble gases doesn't have 8 electrons in the outer shell - ANSWER helium, has only two electrons. boiling points of noble gasses - ANSWER increase with increasing relative atomic mass. (going down the group) explain how properties of the elements in Group 0 depend on the outer shell of electrons of the atoms - ANSWER the boiling points of the elements increase as you go down the group as the number of shells increase which enhances the intermolecular forces between the atoms, requiring more energy to break these forces as the atomic size increases. predict properties from given trends down the group. - ANSWER what are elements in group 1 known as - ANSWER the alkali metals, have characteristic properties because of single electron in outer shell. describe the reactions of the first three alkali metals with oxygen, chlorine and water. - ANSWER Lithium = reacts with oxygen to form lithium oxide and with chlorine to form lithium chloride. Sodium = reacts with oxygen to form sodium oxide and with chlorine to form sodium chloride potassium = reacts with oxygen to form potassium oxide and with chlorine to form potassium chloride. reactions are characterized by formation of Hydroxide ions and the release of hydrogen gas, common outcome in reactions of alkali metals with water. trend with reactivity of elements in group 1. - ANSWER reactivity increases going down group. explain how properties of the elements in Group 1 depend on the outer shell of electrons of the