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Science C3 Topic 5

GCSE edexcel further additional chemistry: organic chemistry

What is fermentation? Fermentation is when microorganisms break down large molecules using enzymes
What are the desirable conditions for fermentation? * Anaerobic conditions - if oxygen is present then yeast will respire aerobically, producing only carbon dioxide and water * Warm temperature - if the temperature is too low the reaction is slow, and if the temperature is too high the yeast is killed
What makes alcohol drinks different? They contain different percentages of ethanol - drinks are rated in terms of the number of units of ethanol that they contain
What are the impacts of drinking alcoholic drinks on the drinker? Short-term: *Slower reaction times *Violent/aggressive behaviour *Loss of balance & coordination *Vomiting & fainting *Dehydration -> hangover Long-term: *Liver cirrhosis *Increases risk of heart disease and stroke
What are the impacts of drinking alcoholic drinks on society? *Lots of money is spent on helping those with alcohol-related medical conditions *Can cause anti-social behaviour and disorder in public places
What are the three ways that ethanol can be produced? * fermentation of glucose by yeast * fractional distillation of fermentation mixture * hydration of ethene
How is ethanol produced by the fermentation of glucose? Yeast is a single-celled fungus that breaks down glucose sugar into ethanol and carbon dioxide by aerobic respiration. The yeast cells release the enzymes for this reaction. The reaction is done at 30-40º as it is the optimum temperature for enzymes
How is ethanol produced by fractional distillation? 1. Fermentation mixture is heated 2. Vapour rises up fractionating column - fraction of the liquid that boils first will contain a higher proportion of ethanol (ethanol boiling point: 78ºC) 3.Vapour condenses + liquid is collected, up to 95% ethanol
How is ethanol produced by the hydration of ethene? Ethene is a hydrocarbon, produced by fractional distillation of crude oil + cracking larger molecules in higher-boiling fractions of crude oil. Ethene is reacted with steam in the presence of a catalyst - hydration reaction, water is added to ethene
What is the reverse of this reaction? This reaction can be reversed in a dehydration reaction - heating ethanol to a high temperature in the presence of a suitable catalyst produces ethene and steam
What are some advantages/ disadvantages of producing ethanol by: fermentation of glucose? Advantages: uses biofuels (sugar cane, sugar beet) which are renewable as they can be regrown Disadvantages: produces ethanol solution of only 15% concentration because higher concentrations deactivate the yeast, dependent on crop availability/ climate
What are some advantages/ disadvantages of producing ethanol by: fractional distillation of fermentation mixture? Advantages: uses biofuels (sugar cane, sugar beet) which are renewable as they can be regrown Disadvantages: dependent on the availability of crops and how easily they can be grown in different climates
What are some advantages/ disadvantages of producing ethanol by: hydration of ethene? Advantages: produces nearly 100% pure ethanol, little or no waste products Disadvantages: crude oil is a non-renewable, finite resource
What is a homologous series? A series of compounds which have features: *shared functional group *shared general formula *similar chemical properties *physical properties show a gradation eg. boiling points of alcohols alkanes + alkenes increase as no. of carbon atoms increases
What are the boiling points of the first three alcohols? methanol:-164 ethanol: -88 propanol: -42
Describe the features of the alkanes * Functional group = only single bonds * Suffix = -ane * General formula = CnH2n+2 * Hydrocarbons * e.g. methane CH4 (one carbon atom with four hydrogen atoms around it, single bonds)
Describe the features of the alkenes * Functional group = double carbon-carbon bond * Suffix = -ene * General formula = CnH2n * Hydrocarbons * e.g. ethene C2H4 (a carbon-carbon double bond, 2 hydrogen atoms coming off either carbon atom)
Describe the features of the alcohols * Functional group = hydroxyl group (O-H) * Suffix = -ol * General formula = CnH2n+1OH * e.g. propanol C3H5OH
Describe the features of the carboxylic acids * Functional group = carboxyl group (COOH) * Suffix = -oic acid * General formula = C(n-1)H(2n-1)COOH = CnH2nO2 * e.g. propanoic acid C3H5OH
What forms when ethanol is oxidised? When does this occur? Ethanol can be oxidised to form ethanoic acid in aerobic reaction - this occurs when bottles of wine are left open
Ethanoic acid is found in what foodstuff? It is the main content of vinegar
What is ethanoic acid used for? • Ethanoic acid is a flavouring as it gives food a tangy, sharp taste • It is also a preservative - for example some foods are pickled (stored in vinegar) and the foods last longer because bacteria can’t survive in the acidic environment
What shows that ethanoic acid acts as a normal acid? * It turns litmus paper and universal indicator red * It forms ethanoate salts when they react with metals, metal hydroxides, bases and carbonates
Metal + acid -> ? Salt + hydrogen
Metal hydroxide + acid -> ? Salt + water (it is a neutralisation reaction, as hydroxides are bases)
Metal oxide + acid -> ? Salt + water (it is a neutralisation reaction as oxides are bases)
Metal carbonate + acid -> ? Salt + water + carbon dioxide
sodium hydroxide + propanoic acid -> ? Sodium propanoate + water
Magnesium + ethanoic acid -> ? Magnesium ethanoate + hydrogen
What is an ester? Esters are compounds made when carboxylic acids react with alcohol
What is the reaction involving a carboxylic acid and an alcohol? Carboxylic acid + alcohol -> ester + water
methanoic acid + propanol -> ? propyl methanoate + water
What are the uses of esters? * Used in perfumes, they are pleasant-smelling * Used as flavourings in sweets * Make polyesters (long chain of esters that can be made into fibres -> woven into fabrics)
What can polyesters be recycled into? Fleece clothing and fibres e.g in a carpet
Created by: 11043