IGCSE Edexcel Chemistry Definitions
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Questions and Answers

What is a hydrocarbon?

Carbon and hydrogen atoms only.

What are the characteristics of a homologous series?

  • Similar chemical properties
  • Trend in physical properties
  • Same functional group
  • All of the above (correct)

    • What is a functional group?

    A group of atoms within a molecule that causes the molecule to react in a specific way.

    What is an isomer?

    <p>Same molecular formula, different structural formula.</p> Signup and view all the answers

    What type of reaction is represented by A + B -----> C?

    <p>Addition.</p> Signup and view all the answers

    What is crude oil?

    <p>A mixture of hydrocarbons.</p> Signup and view all the answers

    How is crude oil separated?

    <p>Fractional distillation.</p> Signup and view all the answers

    What are fractions crude?

    <p>Hydrocarbons with similar boiling points separated from crude oil.</p> Signup and view all the answers

    What is boiling point?

    <p>The temperature at which a liquid changes to a gas.</p> Signup and view all the answers

    Why do longer hydrocarbon chains have higher boiling points than shorter hydrocarbon chains?

    <p>Stronger intermolecular forces.</p> Signup and view all the answers

    How does the boiling point of the fractions of crude oil change going down the column?

    <p>Increases.</p> Signup and view all the answers

    How does the boiling point of the fractions of crude oil change going up the column?

    <p>Decreases.</p> Signup and view all the answers

    How does the color of the fractions of crude oil change going down the column?

    <p>Get darker.</p> Signup and view all the answers

    What is viscosity?

    <p>Resistance to flow.</p> Signup and view all the answers

    How does the viscosity of the fractions of crude oil change going down the column?

    <p>More viscous.</p> Signup and view all the answers

    What is fuel?

    <p>A substance that releases heat energy when it burns.</p> Signup and view all the answers

    What are the products of complete combustion?

    <p>Carbon dioxide and water</p> Signup and view all the answers

    What are the products of incomplete combustion?

    <p>Carbon monoxide and water</p> Signup and view all the answers

    What condition is required for incomplete combustion?

    <p>Limited supply of oxygen.</p> Signup and view all the answers

    Which gas from the combustion of hydrocarbons is poisonous?

    <p>Carbon monoxide.</p> Signup and view all the answers

    Why is carbon monoxide poisonous?

    <p>Binds irreversibly to haemoglobin, reduces the capacity of blood to transport oxygen.</p> Signup and view all the answers

    What factor allows nitrogen and oxygen to react in car engines?

    <p>High temperature.</p> Signup and view all the answers

    Name an environmental problem related to nitrogen oxides.

    <p>Acid rain.</p> Signup and view all the answers

    Name an environmental problem related to sulphur oxides.

    <p>Acid rain.</p> Signup and view all the answers

    What is the sulfur product formed during the combustion of hydrocarbons containing impurities such as sulphur?

    <p>Sulfur dioxide.</p> Signup and view all the answers

    What conditions are needed for cracking?

    <p>Alumina (Al2O3) catalyst / Silica (SiO2) catalyst, 650ºC.</p> Signup and view all the answers

    Cracking converts ____ chain alkanes into ____ chain alkanes and alkenes.

    <p>Long, Shorter</p> Signup and view all the answers

    Cracking produces a shorter alkane and an ___?

    <p>Alkene.</p> Signup and view all the answers

    Why is cracking important?

    <p>Long chain alkanes are converted into more useful shorter chain alkanes and alkenes which are in higher demand.</p> Signup and view all the answers

    What is the general formula for alkanes?

    <p>CnH2n+2.</p> Signup and view all the answers

    What is a saturated hydrocarbon?

    <p>A hydrocarbon with single bonds only.</p> Signup and view all the answers

    What is the required condition for the reaction CH4 + Cl2 ---> CH3Cl + HCl?

    <p>Ultraviolet light (UV).</p> Signup and view all the answers

    What is the functional group of alkenes?

    <p>C=C (Carbon-Carbon double bond).</p> Signup and view all the answers

    What is the general formula for alkenes?

    <p>CnH2n.</p> Signup and view all the answers

    What is an unsaturated hydrocarbon?

    <p>Hydrocarbon with one or more double or triple bonds.</p> Signup and view all the answers

    What test can be used to determine saturation in hydrocarbons?

    <p>Bromine water.</p> Signup and view all the answers

    What is the formula of bromine water?

    <p>Br2 (aq).</p> Signup and view all the answers

    What chemical test can be used to distinguish between an alkane and an alkene?

    <p>Bromine water. Colour change for Alkene, no colour change for Alkane.</p> Signup and view all the answers

    What is the functional group of alcohols?

    <p>-OH.</p> Signup and view all the answers

    What is microbial oxidation?

    <p>Reaction of ethanol with oxygen in the air to form ethanoic acid.</p> Signup and view all the answers

    What are the conditions for fermentation of glucose?

    <p>30ºC, anaerobic conditions (absence of air), yeast (biological catalyst).</p> Signup and view all the answers

    What are the conditions for the hydration of ethene?

    <p>300ºC, 60-70 atm pressure, phosphoric acid catalyst.</p> Signup and view all the answers

    What is an advantage of fermentation?

    <p>Renewable starting material (glucose).</p> Signup and view all the answers

    What is a disadvantage of fermentation?

    <p>Slow rate of reaction, low purity of alcohol.</p> Signup and view all the answers

    What is an advantage of the hydration of ethene?

    <p>High purity, fast rate of reaction.</p> Signup and view all the answers

    What is a disadvantage of the hydration of ethene?

    <p>Expensive.</p> Signup and view all the answers

    What does the fermentation of glucose produce?

    <p>Ethanol.</p> Signup and view all the answers

    What conditions are needed for oxidation?

    <p>Potassium dichromate (VI), sulphuric acid, heat.</p> Signup and view all the answers

    What is the carboxylic acid functional group?

    <p>COOH.</p> Signup and view all the answers

    What carboxylic acid does vinegar contain?

    <p>Ethanoic acid.</p> Signup and view all the answers

    What is the functional group of esters?

    <p>-COO-.</p> Signup and view all the answers

    What catalyst is used in esterification reactions?

    <p>Sulphuric acid.</p> Signup and view all the answers

    What are the properties of esters?

    <p>All of the above</p> Signup and view all the answers

    What are some uses of esters?

    <p>All of the above</p> Signup and view all the answers

    What is a monomer?

    <p>Small molecule unit that makes up a polymer.</p> Signup and view all the answers

    What is a polymer?

    <p>A long chain molecule formed from joining many small molecules (called monomers).</p> Signup and view all the answers

    What is a disadvantage of burning polymers?

    <p>Toxic gases.</p> Signup and view all the answers

    What is a disadvantage of landfill disposal for polymers?

    <p>Non biodegradable.</p> Signup and view all the answers

    What is a biopolyester?

    <p>Biodegradable polyester.</p> Signup and view all the answers

    What is condensation polymerization?

    <p>Chemical reaction in which monomers join together to form a polymer and a small molecule.</p> Signup and view all the answers

    What is a diol?

    <p>A molecule with two alcohol groups.</p> Signup and view all the answers

    What is a dicarboxylic acid?

    <p>A molecule with two carboxylic acid groups.</p> Signup and view all the answers

    What two chemicals are needed to make a polyester?

    <p>Diol, dicarboxylic acid.</p> Signup and view all the answers

    What is the term for heat given out?

    <p>Exothermic.</p> Signup and view all the answers

    What is the term for heat taken in?

    <p>Endothermic.</p> Signup and view all the answers

    What happens to temperature during an exothermic reaction?

    <p>Temperature increases.</p> Signup and view all the answers

    What happens to temperature during an endothermic reaction?

    <p>Temperature decreases.</p> Signup and view all the answers

    What does a positive enthalpy change mean?

    <p>Endothermic.</p> Signup and view all the answers

    What does a negative enthalpy change mean?

    <p>Exothermic.</p> Signup and view all the answers

    What is the equation for heat energy change?

    <p>Q = mcΔT.</p> Signup and view all the answers

    What is the equation for molar enthalpy change?

    <p>ΔH = -Q / 1000 n.</p> Signup and view all the answers

    Is bond breaking exothermic or endothermic?

    <p>Endothermic</p> Signup and view all the answers

    Is making bonds exothermic or endothermic?

    <p>Exothermic</p> Signup and view all the answers

    What is the equation for enthalpy change using bond energies?

    <p>ΔH = ΣBonds broken - ΣBonds made.</p> Signup and view all the answers

    Increasing the surface area of a solid affects the rate of reaction how?

    <p>Increases.</p> Signup and view all the answers

    Powder reactants react faster than lumps.

    <p>True</p> Signup and view all the answers

    Increasing the concentration of solutions affects the rate of reaction how?

    <p>Increases.</p> Signup and view all the answers

    Increasing the pressure of reacting gases affects the rate of reaction how?

    <p>Increases.</p> Signup and view all the answers

    Increasing the temperature affects the rate of reaction how?

    <p>Increases.</p> Signup and view all the answers

    Why does increasing concentration increase the rate of reaction?

    <p>More particles per unit volume, more frequent successful collisions.</p> Signup and view all the answers

    Why does increasing pressure increase the rate of reaction?

    <p>Particles are squeezed closer together, more frequent successful collisions.</p> Signup and view all the answers

    Why does increasing surface area increase the rate of reaction?

    <p>More exposed particles can react, more frequent successful collisions.</p> Signup and view all the answers

    Why does increasing temperature increase the rate of reaction?

    <p>Particles move faster, more particles exceed activation energy, more frequent successful collisions.</p> Signup and view all the answers

    What is a catalyst?

    <p>A substance that speeds up the rate of a chemical reaction.</p> Signup and view all the answers

    Why does adding a catalyst increase the rate of reaction?

    <p>Catalyst offers an alternative reaction pathway with a lower activation energy.</p> Signup and view all the answers

    What does the symbol ⇌ mean?

    <p>Reversible reaction.</p> Signup and view all the answers

    What would you observe in the reversible reaction: CuSO4.5H2O ⇌ CuSO4 + 5H2O?

    <p>Colour change: blue to white.</p> Signup and view all the answers

    What condition is needed for a reaction to reach dynamic equilibrium?

    <p>A closed system.</p> Signup and view all the answers

    What are the two characteristics of a dynamic equilibrium?

    <p>The forward and reverse reactions occur at the same rate; the concentrations of reactants and products remain constant.</p> Signup and view all the answers

    Why does a catalyst not affect the position of equilibrium?

    <p>Catalysts speed up the rate of forward and reverse reaction equally.</p> Signup and view all the answers

    Increasing temperature favors which type of reaction?

    <p>Endothermic.</p> Signup and view all the answers

    Decreasing temperature favors which type of reaction?

    <p>Exothermic.</p> Signup and view all the answers

    Increasing pressure favors the side with what?

    <p>Fewer moles of gas.</p> Signup and view all the answers

    Decreasing pressure favors the side with what?

    <p>More moles of gas.</p> Signup and view all the answers

    What is the test for oxygen gas?

    <p>Relights a glowing splint.</p> Signup and view all the answers

    What is the test for carbon dioxide?

    <p>Turns limewater cloudy.</p> Signup and view all the answers

    What is the test for ammonia gas?

    <p>Damp red litmus paper turns blue.</p> Signup and view all the answers

    What is the test for chlorine gas?

    <p>Bleaches damp litmus paper.</p> Signup and view all the answers

    What is the name of group 1 elements?

    <p>Alkali metals.</p> Signup and view all the answers

    How does the reactivity of group 1 elements change?

    <p>Increases down the group.</p> Signup and view all the answers

    Study Notes

    Hydrocarbons

    • Composed solely of carbon and hydrogen atoms.
    • Crude oil is a mixture of hydrocarbons.

    Homologous Series

    • Features similar chemical properties and physical property trends.
    • Defined by a common functional group.

    Functional Groups and Isomerism

    • Functional groups determine the reactivity of organic molecules.
    • Isomers share the same molecular formula but have different structural arrangements.

    Reactions and Distillation

    • An addition reaction is represented as A + B → C.
    • Crude oil is separated through fractional distillation, isolating hydrocarbon fractions with similar boiling points.

    Boiling Points and Viscosity

    • Longer hydrocarbon chains exhibit higher boiling points due to stronger intermolecular forces.
    • Viscosity refers to a substance's resistance to flow; in crude oil fractions, viscosity increases down the column.

    Combustion Products

    • Complete combustion produces carbon dioxide and water.
    • Incomplete combustion yields carbon monoxide or carbon and water, occurring in limited oxygen supply.

    Nitrogen and Sulfur Compounds in Combustion

    • Carbon monoxide is a toxic gas formed during combustion.
    • Nitrogen oxides and sulfur oxides contribute to acid rain, posing environmental issues.

    Cracking and Alkanes

    • Cracking converts long-chain alkanes into shorter ones and alkenes, useful for meeting demand.
    • Catalysts like alumina and silica are used at high temperatures (650ºC).

    Saturation and Functional Groups

    • Alkanes: saturated hydrocarbons characterized by single bonds. General formula: CnH2n+2.
    • Alkenes: unsaturated hydrocarbons with at least one double bond (C=C). General formula: CnH2n.

    Testing for Unsaturation

    • Bromine water changes color from orange to colorless in the presence of alkenes, distinguishing them from alkanes.

    Alcohols and Carboxylic Acids

    • Alcohols have the functional group (-OH).
    • Ethanoic acid (vinegar) is a common carboxylic acid with the functional group (COOH).

    Esterification and Polyesters

    • Esters are formed by reacting an alcohol and a carboxylic acid with a sulfuric acid catalyst.
    • Biopolyesters are environmentally friendly due to their biodegradable properties.

    Energy Changes in Reactions

    • Exothermic reactions release heat and lead to temperature increases; endothermic reactions absorb heat and decrease temperature.

    Reaction Rates

    • Increasing surface area, concentration, temperature, or pressure accelerates reaction rates due to more frequent successful collisions.
    • Catalysts lower activation energy, promoting faster reactions without altering equilibrium positions.

    Dynamic Equilibrium

    • Achieved in a closed system where the rates of forward and reverse reactions are equal, with constant concentrations.
    • Temperature, pressure, and concentration shifts influence equilibrium favoring either exothermic or endothermic reactions.

    Gas Tests

    • Oxygen relights a glowing splint; carbon dioxide turns limewater cloudy; ammonia turns damp red litmus paper blue; chlorine bleaches damp litmus paper.

    Chemical Properties of Group 1 Elements

    • Group 1 elements are known as alkali metals and exhibit increased reactivity down the group.

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