paper 2

• what is a reversible reaction


  works both waysr --> <--
• what is equilibrium 


  forwards and backwards reaction occurring at the same rate
• what does equilibrium depend on?

  temp, pressure, concentration
• what is a closed system?

  none of reactants of products can escape
• closed system 


  nothing can get in
• what does a reversible reaction reach? 


  equilibrium
• Exothermic reaction


  Reaction in which energy is given out to the surroundings, causing the temperature of the surroundings to increase
• Endothermic reaction


  Reaction in which energy is taken in from the surroundings, causing the temperature of the surroundings to decrease
• Exothermic reactions


  • Combustion reactions
  • Many oxidation reactions
  • Most neutralisation reactions
• Endothermic reactions


  • Thermal decomposition reactions
  • Reaction of citric acid and sodium hydrogencarbonate
• Energy is conserved in chemical reactions, so the total amount of energy in the universe at the end of a reaction is the same as it was before the reaction
• In exothermic reactions


  Energy exits
• In endothermic reactions


  Energy enters
• Everyday uses of exothermic reactions include self-heating cans and hand warmers
• Everyday uses of endothermic reactions include instant ice packs which can be used to treat sports injuries
• Exothermic reaction between dilute sodium hydroxide and hydrochloric acid

  1. Sodium hydroxide solution is poured into a beaker of hydrochloric acid

  2. The beaker now contains sodium chloride and water

  3. The thermometer is showing a rise in temperature, so the neutralisation reaction is exothermic
• Endothermic reaction between sodium carbonate and ethanoic acid

  1. Sodium carbonate powder is tipped into a beaker of ethanoic acid

  2. The beaker now contains sodium ethanoate, water and carbon dioxide

  3. The thermometer is showing a fall in temperature, so this was an endothermic reaction
• Hydrocarbon


  A compound that contains hydrogen and carbon only
• Compound


  A substance formed by the chemical union of two or more elements
• Atom


  The smallest part of an element that can exist
• Crude oil


  Mixture of hydrocarbons, mainly alkanes, formed over millions of years from the remains of ancient dead marine organisms
• Crude oil


  • It is a finite resource that is found in the Earth's crust
  • It is the remains of organisms that lived and died millions of years ago - mainly plankton which was buried in mud
• Mixture

  Two or more substances that are not joined together. The substances can be elements, compounds, or both
• Hydrocarbon molecules


  • Chains and rings of carbon atoms with hydrogen atoms
• Fuel


  Material that is used to produce heat, like coal, oil or gas
• Petrochemical


  Substance made from crude oil using chemical reactions
• Substances made from compounds in crude oil

  • Ethene
  • Poly(ethene)
  • Solvents
  • Lubricants
  • Detergents
• Crude oil is an important source of fuels and feedstock for the petrochemical industry
• Crude oil is a finite resource
• Petrol and other fuels are produced from crude oil using fractional distillation
• Cracking is used to convert long alkanes into shorter, more useful hydrocarbons
• Alkanes


  Saturated hydrocarbons - compounds containing hydrogen and carbon only, with no C=C bonds
• General formula for alkanes


  CnH2n+2, where n is the number of carbon atoms
• Alkanes


  • Decane
  • Hexane
• Covalent bonds in alkanes are not really at 90 degree angles, as shown in the structures
• Alkanes are saturated hydrocarbons - they contain no carbon-to-carbon double bonds, only single bonds
• Crude oil


  Mixture of hydrocarbons, mainly alkanes, formed over millions of years from the remains of ancient dead marine organisms
• Fractional distillation


  A method used to separate a mixture of several substances, such as crude oil, into simpler, more useful mixtures by distilling and collecting the evaporated components as they condense at different temperatures
• Crude oil is a finite resource
• Petrol and other fuels are produced from crude oil using fractional distillation