Chemistry - AQA GCSE
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Chemistry - AQA GCSE - Marcador
Chemistry - AQA GCSE - Detalles
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| 🇬🇧 | 🇬🇧 |
| How is an ion formed? | From an element losing/gaining an electron |
| What is sublimation? | Solid -> gas OR gas -> solid |
| How is a solution formed? | When a solute dissolves in a solvent |
| What's the formula for concentration | Concentration (g/dm^3) = mass of solute (g) ÷ volume (dm^3) |
| How can concentration be increased? | 1) by dissolving more solute in a given volume of solution - this increases the mass of the solute 2) by allowing some of the solvent to evaporate - this decreases the volume of the solution |
| What's the equation linking No. of Particles, Avogadro's constant & amount(mol)? | No. of particles = Avogadro's constant × amount of substance in mol |
| What's the equation linking Mass, Rfm & amount(mol)? | Mass = relative formula mass × amount |
| In a balanced equation, what shows the amount(mol) of products and reactants? | The coeficient (number infront of formulae). No coefficient means 1 mol |
| What is a limiting reactant? | The reactant that is all used up. This is what The mass of product formed in a reaction depends on |
| What's the excess? | The reactant that is left over |
| 12 g of magnesium reacts completely with excess hydrochloric acid to form magnesium chloride and hydrogen: Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g) Calculate the maximum mass of hydrogen that can be produced. (Ar of Mg = 24, Mr of H2 = 2) | Amount of magnesium = mass ÷ rfm Amount of magnesium = 12/24 = 0.5 mol Looking at the equation, 1 mol of Mg forms 1 mol of H2, so 0.5 mol of Mg forms 0.5 mol of H2 Mass of H2 = Mr × amount = 2 × 0.5 = 1 g |
| What's the equation for concentration? | Concentration(mol/dm^3) = amount of solute(mol) ÷ volume (dm^3) REMEMBER: × by 100 to go from dm^3 to cm3 |
| How do you convert between mol/dm^3 to g/dm^3 (vice versa)? | '×' by the rfm (to go from g/dm^3 to mol/dm^3 '÷' by the rfm) |
| What happens when a metal reacts with water? | A metal hydroxide and hydrogen are formed e.g. Sodium + water --> sodium hydroxide + hydrogen 2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g) |
| What happens when a metal reacts with a dilute acid? | A salt and hydrogen are formed e.g. Magnesium + hydrochloric acid → magnesium chloride + hydrogen Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g) |
| What happens when a metal reacts with a metal oxide? | This is an oxidation reaction as the metal gains oxygen and a metal oxide is formed e.g. Magnesium + oyxgen → magnesium oxide 2Mg(s) + O2(g) → 2MgO(s) |
| What is a displacement reaction? | When a more reactive metal can displace a less reactive metal from its compounds. |
| Describe ways to mesure rate of reaction. | 1)Mesuring mass change -effective when carbon dioxide is produced as it leaves reaction container -innefective for gases with small rfm like hydrogen 2)Mesuring volume change -useful when gas leaves container - mesured in gas syringe or burette or mesuring cylinder 3)Graph -mass/volume of product on Y axis Time on X axis -gradient equal to rate of reaction (steep gradient fast reaction) |
| How does an increase in concentration, pressure and surface area affect rate of reaction? | 1)reactant particles become more crowded 2)frequency of collisions between reactant particles increases 3)the rate of reaction increases ENERGY DOESNT CHANGE |
| How does increased surface area affect rate of reaction? | 1)higher surface area to volume ratio 2)more reactant particles are exposed 3)Frequency of collisions increases |
| How does increased temperature affect rate of reaction? | 1)reactant particles move quicker 2)energy of particles increases 3)proportion of successful collisions increases 4)rate of reaction increases |
| What is a successful collision? | A colllision between reactant particles that has enough energy (activation energy or more) to produce a reaction |
| What is a catalyst how does it work? | A substance the changes the rate of reaction without being changed itself it finds an alternative reaction pathway that has a lower activation energy than the uncatalysed reaction thus increasing the frequency of successful colisions |
| Required practical to mesure the effect of concentration | 1)Support gas syringe with a stand, boss and a clamp 2)Add 50cm3 dilute hydrochloric acid to conical flask 3)Add 0.4g calcium carbonate to the flask attach the syringe and imediately start the stopwatch 4)Record gas collected every 10 seconds 5)Clean aparatus and reapat with different concentrations |
| Required practical to mesure temperature change? | 1)Add 50cm3 sodium thiosulphate soloutuion to conical flask 2)Mesure initial temperature 3)Place conical flask on paper with black cross 4)Add 10cm3 dilute hydrochloric acid to the conical flask start stopwatch 5)When black cross is no longer visible record the time on the stopwatch 6)Record temperature of reaction mixture 7)Clean aparatus and repeat with different temperatures of thiosulphate |
| 3 Properties of Alkanes (& Structure)? | - Form a homologous series - Have similar chemical properties - Are saturated (C-C single bonds) STRUCTURES(CnH2n+2): - Methane: CH4 - Ethane: C2H6 - Propane: C3H8 - Butane: C4H10 |
| How does Fractional Distillation Work? | Seperates crude oil into simpler more useful mixtures. Works because different hydrocarbons have different boiling points: 1) heated crude oil enters a tall fractionating column, which is hot at the bottom and gets cooler towards the top 2) vapours from the oil rise through the column 3) vapours condense when they become cool enough 4) liquids are led out of the column at different heights |
| In/complete Combustion of Hydrocarbon Fuels | Complete - good oxygen supply, exothermic, CO2 and water produced, max amount of energy is given out (Bunsen burner hole fully open) Incomplete - Poor oxygen supply. water, carbon monoxide & carbon produced, less energy released than complete combustion (fully closed Bunsen burner hole) |
| Common properties in a Homologous Series | - Same general formula - differ by CH2 in molecular formulae from neighbouring compounds - Show gradual variation in physical properties (boiling points) - Similar chemical properties |
| Compare Small & Big hydrocarbon molecules | Small hydrocarbon molecules: - are very volatile - flow easily - ignite easily as they have weak intermolecular forces, therefore they have low boiling points - They do not condense, but leave the column as gases OPPOSITE FOR BIG HYDROCARBONS |
| Definition & Uses of Crude Oil | 1) Complex mixture of hydrocarbons 2) A finite resource found in earth's crust 3) It's the remains of organisms that lived and died millions of years ago - mainly plankton which was buried in mud USES: - Fuels like petrol, diesel, kerosene, heavy fuel oil & liquefied petroleum gases - Feedstock for the petrochemical industry - Solvents - Lubricants - Detergents |
| The 6 Fractions and Their Uses? | (25°C - top) 1) Liquefied Petroleum Gases - fuel for heating/cooking 2) Petrol - Car fuel 3) Kerosene - Aircraft fuel 4) Diesel - Car/train fuel 5) Heavy Fuel Oil - Ship/power station fuel 6) Bitumen - for roads and roofs (350°C - bottom) |
| 2 Types of Cracking | Alkane -> alkane(CnH2n+2) + alkene (CnH2n) CATALYCTIC CRACKING: uses a temperature of approximately 550°C and a catalyst (zeolite, which contains aluminium oxide and silicon oxide) STEAM CRACKING: uses a higher temperature of over 800°C, no catalyst |
| Alkanes | Methane: CH4 Ethane: C2H6 Propane: C3H8 Butane: C4H10 |
| How can you tell the difference between a pure substance and a mixture? | A pure substance has a sharp melting point but mixtures melt over a range of temperatures |
| What is a formulation? | A mixture designed as a useful product e.g. fuels, cleaning products, paint |
| How can u tell if a substance is pure through a chromatogram? | A pure substance has one spot but an impure substance will produce 2 or more spots. |
| Chromotography required practical? | 1)draw a pencil line across the chromatography paper, 1 - 2 cm from the bottom 2)use a pipette or capillary tube to add small spots of each ink to the line on the paper 3)place the paper into a container with a suitable solvent in the bottom 4)allow the solvent to move through the paper, but remove the chromatogram before it reaches the top 5)allow the chromatogram to dry, then measure the distance traveled by each spot and by the solvent |
| Earths Early Atmosphere VS Today | EARTH'S EARLY ATMOSPHERE(approx 4.6 billion years ago): - large amount of carbon dioxide - little or no oxygen - small amounts of other gases (ammonia and methane..) Volcanic activity also released water vapour, which condensed(as earth cooled) forming the oceans. Nitrogen was probably released too & gradually built up in the atmosphere as its unreactive. EARTH'S ATMOSPHERE TODAY: - Nitrogen: 80% roughly - oxygen: 20% roughly - Other gases (CO2, water vapour, noble gases...): the rest |
| Explain the Oxygen Increase & Carbon Dioxide Decrease | OXYGEN INCREASE: Believed algae evolved about 2.7 billion years ago, photosynthesised, oxygen in atmosphere increased, enabling animals to evolve CARBON DIOXIDE DECREASE: 1) oceans formed, carbon dioxide dissolved to form soluble carbonate compounds which then precipitated as sedimentary rocks (limestone). 2) absorbed from the oceans into photosynthetic algae and plants. Crude oil and natural gas were formed from simple plants and tiny animals which were living in oceans and lakes 3) Over millions of years, heat and pressure turned the remains of the organisms into crude oil and natural gas 4) Coal is a fossil fuel which was formed from trees which were in dense forests in low-lying wetland areas, floods, buried them away(stopping them from being oxidised), compressed and heated over millions of years. |
| No flash cards | No flashcards |
| What is simple distillation used for and how does it work? | Used to separate a solvent from a solution, works because the dissolved solute has a much higher boiling point than the solvent |
| What is the radius of the an Atom & a Nucleus | Atom's radius = 1 × 10^-10 m Radius of a Nucleus =1 × 10^-14 m |
| What is the Atomic Number? | The number of protons in an atom (this defines what element an element is) |
| What is the Mass Number? | Protons + Neutrons |
| What are isotopes? | Atoms of the same element with a different number of neutrons (same atomic no. but different mass no.) |
| What does the electron determine? | An elements chemical properties |
| Whats the relative atomic mass? | Average mass of the atoms of the isotopes, calculated from: - the mass numbers of its isotopes - the abundance(plentifulness) of these isotopes |
| What did John Dalton do? | JOHN DALTON: 1- Published his ideas in 1803 2- All matter was made of tiny spheres that cant be divided - atoms JJ THOMSON: 1- Nearly 100 years later, discovered electrons 2- Plum pudding model: ball of + charge, - electrons embedded ERNEST RUTHERFORD: 1- Positive charged alpha particles fired at thin gold foil 2- most went through: mostly empty space 3- few scattered in all directions: positively charged nucleus concentrated at atoms centre NIELS BOHR: 1- Did calculations& experiments: electrons orbit the nucleus in shells at fixed distances FURTHER EXPERIMENTS: 1- Protons: positive charge JAMES CHADWICK: 1- 1932, found evidence for mass in nucleus with no charge - neutrons |
| What did Dmitri Mendeleev do in his periodic table? | Publish his first book in 1869: - Arranged elements in terms of increasing atomic weight - took into account the properties of the elements and their compounds - left gaps for undiscovered elements - showed elements with similar chemical properties lined up in groups - swapped positions of some elements (eg, iodine & tellurium) due to similar chemical properties, despite their weight being in the wrong order |
| What are Periods in increasing order of? | Atomic Number |
| What do groups categorize elements in terms of? | Similar Properties |
| How can you tell if an element is a metal? | In chemical reactions metal atoms lose electrons to form positive ions. |
| What chemical properties indicate if an element is a non-/metal? | Most metal oxides are basic most non-metal oxides are acidic |
| What physical properties indicate if an element is a non-/metal? | Most metals have high melting and boiling points most non-metals have low melting and boiling points |
| What are the Physical Properties of the Noble Gases? | - low boiling points (helium - lowest) As you go down: - attractive forces between them become stronger - atoms become larger - the intermolecular forces between atoms get stronger - more energy needed to overcome these forces |
| Why are the noble gases inert(unreactive)? | They have a full outer shell ∴ stable electron arrangements ∴ they have no tendency to loose or gain electrons and are unreactive |
| What are the physical properties of the alkali metals (Group 1)? | Are soft (can be cut with a knife) have relatively low melting points have low densities |
| Why do elements in a group have similar chemical properties? | They have the same amount of electrons on their outer shell |
| What happens when alkali metals react with water (give an example)? | Alkali metal + water → metal hydroxide + hydrogen |
| What happens when sodium reacts with water | Sodium + water → sodium hydroxide + hydrogen Sodium hydroxide is an alkali and a base that dissolves in water to form an alkaline solution which: - has a pH greater than 7 - turns universal indicator solution blue or purple |
| What happens when the alkali metals react with oxygen? | 1) Room temp - oxygen reacts with metals surface forming a white oxide which covers the surface (metal below the surface doesn't react) 2) When heated - burn vigorously, oxide forms as white smoke 3) The reactivity of these elements increase as you go down |
| What happens when the alkali metals react with chlorine? | Vigorously producing chlorides Room temp - chlorides are white solids that dissolve in water forming colourless solutions Reactions get more vigorous as you go down |
| Explain the trend in reactivity as you go down group 1. | Going down: - the atoms become larger - the outer electron becomes further from the nucleus - the force of attraction between the nucleus and the outer electron decreases - the outer electron is lost more easily AND: the more easily it loses its electron(ion formed), the more reactive the metal |
| Why do melt/boiling points increase the further you go down in Group 7? | - the molecules become larger - the intermolecular forces become stronger - more energy is needed to overcome these forces |
| How do halogens react with metals? | 1) halogens + metal -> salt 2) Salts are made of ions which are held by ionic bonds 3) The reactivity of elements decrease as you go down |
| How do halogens react with non-metals (give an example)? | When reacting with HYDROGEN: - produce a compound: hydrogen halide - which are gases at room temp. - dissolve in water forming acidic solutions Image shows what happens when halogens react with hydrogen: |
| Explain the trend in reactivity of the Halogens | Going down: - the atoms become larger - the outer shell becomes further from the nucleus - the force of attraction between the nucleus and the outer shell decreases - an outer electron is gained less easily - the halogen becomes less reactive |
| Explain displacement reactions of Group 7 (give an example) | More reactive halogens can displace less reactive ones from solutions of its salt EXAMPLE: chlorine + potassium iodide → potassium chloride + iodine |
| What are the physical properties of transition metals? | - they conduct electricity in the solid and liquid states - they are shiny when freshly cut Compare to other metals, most transition metals have: - higher melting points - higher densities - greater strength - greater hardness |
| How do the transition metals react with oxygen compared to group 1 elements | - Group 1 metals react quick with oxygen at room temp - Most transition elements react slowly, or not at all, with oxygen at room temperature (some require heat to react with oxygen) |
| How do the transition metals react with water compared to group 1 elements | REACTION WITH COLD WATER - Group 1 elements: vigorously - Most transition metals: slowly or not at all |
| How do the transition metals react with halogens compared to group 1 elements | - Group 1 elements: vigorously - Some transition metals react with halogens |
| Describe the colour of compounds of transition and 'normal' metals | - Metals: usually form white compounds - Transition elements: form coloured compounds |
| What are catalysts (give 2 examples)? | Substances that increase the rate of reaction without being used up in the reaction: - iron: the catalyst in the Haber process, which makes ammonia - manganese(IV) oxide increases the decomposition of hydrogen peroxide to oxygen and water |
| What is needed for a substance to conduct electricity VS an ionic compound | A SUBSTANCE: - must contains charged particles, such as ions - which particles are free to move from place to place AN IONIC COMPUND: - when it has melted to form a liquid, or - when it has dissolved in water to form an aqueous solution |
| What's the benefit/risks of nanoparticles having a large surface area to volume ratio? | BENEFITS: - Invisible as sunscreens - can be used as catalysts (making reactions more effcient) - used on self-cleaning window panes (catalyse the breakdown of dirt in the presence of sunlight) POSSIBLE RISKS: - Very small, possible to breathe in or pass into cells - Once in the body, may catalyse reactions that are harmful - Risks are hard to identify as modern nanoparticulate materials have only become common recently |
| What are reversible reactions? | Reactions which the products can form the original reactants The arrow in the formula has 2 heads ⇌ e.g. A+B ⇌ C+D |
| What happens if the forward reaction is exothermic? | The backward reaction is endothermic |
| Hydrated definition? | Surrounded by water |
| Dynamic equilibrium definition? | The forward and backward reaction are happening at the same rate. Concentration of all the reacting substances remain constant |
| How can the equilibrium be changed? | 1)Increase in pressure-equilibrium moves to direction of fewest molecules of gas to reduce pressure 2)Increase in concentration-equilibrium moves away from reactant 3)Increase in temperature- equilibrium moves to endothermic reaction to reduce temperature |
| What's the functional Group & Structures of Alcohols? | Functional Group = Hydroxyl group (-OH) STRUCTURE (Cn H2n+1OH): - Methanol: CH3OH - Ethanol: C2H5OH - Propanol: C3H7OH - Butanol: C4H9OH |
| 5 conditions for fermentation. | 1)sugars dissolved in water, & mixed with yeast 2)air lock - allow CO2 out, stop air getting in. If air is present, oxygen oxidises ethanol = ethanoic acid (vinegary) 3)warm temp, 25-35°C 4) Yeast dies when ethanol concentration reaches 15%. 5) Apparatus to investigate fermentation in the lab: Yeast in sugar solution with vegetable oil on top in 1 tube(with cork on top), lime water in another, pipe links tubes together key points: - Anaerobic Process: glucose → ethanol + carbon dioxide - Yeast: A single celled fungus - provides enzymes needed for fermentation. Yeast cells too cold: slow fermentation, too hot: denatured enzymes -Fermentation is v/ slow (takes days/weeks) |
| Condensation polymerisation Process | When 2 monomers react: 1) 2 monomers of different functional groups needed 2) A small molecule (usually water) produced as a by-product 3) Polyesters: Manmade or Biological 4) Making Polyester: monomer which has 2 hydroxyl groups (-OH) + another monomer which has 2 carboxylic groups (-COOH) |
| Describe the Condensation Polymerisation | 1) 2 monomers of different functional groups needed 2) A small molecule (usually water) produced as a by-product |
| Alkene Properties | - Unsaturated (C=C double bond) - React w/ bromine water: orange/brown -> colourless (tests for a double C=C molecule) STRUCTURE (Cn+H2n): Ethene: C2H4 Propene: C3H6 Butene: C4H8 |
| Alcohol: Combustion, Reaction with Sodium, Solubility in Water, Oxidation of Alcohols | 1) Complete Combustion: ethanol + oxygen → carbon dioxide + water (C2H5OH + 3O2 → 2CO2 + 3H2O) - Incomplete Combustion: produces water + carbon monoxide or carbon 2) Reactions with sodium: bubbles of hydrogen gas are produced and the liquid contains sodium ethoxide (2Na + 2C2H5OH → 2C2H5ONa + H2) 3) Solubility in water: alcohols with shorter hydrocarbon chains mix easily to produce a solution, larger hydrocarbon chains may not mix easily (2 distinct layers are left) 4) Oxidation of alcohols: oxidised without combustion = produce carboxylic acids ethanol + oxidising agent → ethanoic acid + water (CH3CH2OH + 2[O] → CH3COOH + H2O) |
| What is the Functional Group & the Structures of Carboxylic acids? | Functional Group = Carboxyl group (-COOH) STRUCTURES(CnH 2n+1COOH): - Methanoic acid: HCOOH - Ethanoic acid: CH3COOH - Propaic acid: C2H5COOH - Butanoic acid: C3H7COOH |
| Acid Properties, Making esters & Weak & Strong Acids | 1) Acid properties: dissolve in water forming acidic solutions; ----react with metals -> salt + hydrogen -react with bases -> salt + water -react with carbonates -> salt + water + CO2 2) Esters: Formed when carboxylic acid react with alcohols. - Esters are organic compunds (-COO- functional group). -Ester have fruity smells & are used as solvents (alcohol + carboxylic acid → ester + water) 3) Weak & Strong Acids: Carboxylic acids are weak - their solutions don't contain many hydrogen ions compared to a solution of strong acid with the same concentration. in a strong solution: molecules fully ionised (vice versa) |
| Definition of Polymer & Polymerisation of Polyethene | A polymer is a substance of high relative formula mass, made up of small repeating units Poly(ethene): - ethene is the monomer, poly(ethene) is the polymer. - The C=C double bond in ethene is involved in the polymerisation reaction. It allows ethene molecules to join together to form poly(ethene) |
| Biological polymers: DNA, Proteins, Starch & Cellulose | DNA: - a polymer which is essential for life, most DNA is a double helix - made from four different types of monomer, which are called nucleotides (the sequence of nucleotides along the DNA molecule is a code for genes) - The genetic information stored in a molecule for DNA is a set of instructions for each organism to stay alive and grow PROTEINS: - biological polymers made inside cells - made from amino acid monomers and have a huge range of roles inside living things (e.g. enzymes are made from proteins) STARCH & CELLULOSE: - made by plants, their monomers are sugar molecules - Starch is used by plants as a way of storing energy as a complex carbohydrate - Cellulose is used to make the strong cell wall which gives plant cells (and therefore plants) strength |
| Amino Acids 3 Features | 1) 2 FUNCTIONAL GROUPS: -NH2 & -COOH 2) Amino Acids are polymerised in cells to make polypeptides and proteins 3) Amino Acids react by condensation polymerisation so for every monomer which is added to the growing polymer chain, one molecule of water is also produced |
| What's the equation for Incomplete & Complete Combustion of Alcohols | - Complete Combustion: ethanol + oxygen → carbon dioxide + water (C2H5OH + 3O2 → 2CO2 + 3H2O) - Incomplete Combustion: produces water + carbon monoxide or carbon |