Energy from Fuels

Energy from Fuels To know how energy from fuels can be measured. (Grade C) To calculate the energy content of a fuel. (Grade B) To explain how to measure energy changes in solution. (Grade A) Keywords: Fuel, Combustion, Exothermic, Endothermic, Joule, Kilojoule,

To know how energy from fuels can be measured. (Grade C) To calculate the energy content of a fuel. (Grade B) To explain how to measure energy changes in solution. (Grade A) Keywords: Fuel, Combustion, Exothermic, Endothermic, Joule, Kilojoule,

To know how energy from fuels can be measured. (Grade C) To calculate the energy content of a fuel. (Grade B) To explain how to measure energy changes in solution. (Grade A) Keywords: Fuel, Combustion, Exothermic, Endothermic, Joule, Kilojoule, Calorimeter allows you to compare energy (metal can with water in it). Equation: Q = mc∆T Q = Energy released m = Mass of water heated (1cm3 = 1g) c = Specific heat capacity (Energy needed to raise 1g by 1C) ∆T = Change in temperature For water its specific heat capacity (c) is 4.2J/gC Per Mole: Q x Molecular Mass Mass of fuel burnt

To know how energy from fuels can be measured. (Grade C) To calculate the energy content of a fuel. (Grade B) To explain how to measure energy changes in solution. (Grade A) Keywords: Fuel, Combustion, Exothermic, Endothermic, Joule, Kilojoule, Example: A + B  C 60cm3 of A contains 0.1 moles. 40cm3 of B contains 0.1 moles. Temperature at start: 20.0C Temperature at end: 26.5C Q = mc∆T Q = mc∆T m = 60g + 40g = 100g c = 4.2 J/gC ∆T = 6.5C Q = 273000 or 2.73kJ This is for 0.1 moles. So for 1 Mole = 10 x 2.73 = 27.3J This is exothermic

To know how energy from fuels can be measured. (Grade C) To calculate the energy content of a fuel. (Grade B) To explain how to measure energy changes in solution. (Grade A) Keywords: Fuel, Combustion, Exothermic, Endothermic, Joule, Kilojoule, Question on p219 – Summary Q2. Question on p221 – Summary Q2.

To know how energy from fuels can be measured. (Grade C) To calculate the energy content of a fuel. (Grade B) To explain how to measure energy changes in solution. (Grade A) Keywords: Fuel, Combustion, Exothermic, Endothermic, Joule, Kilojoule, Exothermic or Endothermic? Exothermic: Energy released to environment. Endothermic: Energy supplied by the environment. Energy released and surrounding increase in temperature. A + B C C A + B  C A + B – These are the REACTANTS C – This is the product Energy gained and surrounding decrease in temperature. A + B

To know how energy from fuels can be measured. (Grade C) To calculate the energy content of a fuel. (Grade B) To explain how to measure energy changes in solution. (Grade A) Keywords: Fuel, Combustion, Exothermic, Endothermic, Joule, Kilojoule, Questions on p223 – Summary Q2 and Q3.

To know how energy from fuels can be measured. (Grade C) To calculate the energy content of a fuel. (Grade B) To explain how to measure energy changes in solution. (Grade A) Keywords: Fuel, Combustion, Exothermic, Endothermic, Joule, Kilojoule, Activation Energy? What is it? The minimum amount of energy needed for a collision between to chemicals to result in a reaction. What do enzymes do? They provide an alternative route to make the products and REDUCE the activation energy needed. Enzymes lower the activation energy. A + B C

To know how energy from fuels can be measured. (Grade C) To calculate the energy content of a fuel. (Grade B) To explain how to measure energy changes in solution. (Grade A) Keywords: Fuel, Combustion, Exothermic, Endothermic, Joule, Kilojoule, Chemical Reactions: For a chemical reaction to take place there needs to be BONDS BEING BROKEN and BONDS BEING FORMED. To break a bond = ENERGY NEEDS TO BE SUPPLIED. To form a bond = ENERGY IS GIVEN OUT. Example: H2 + O2  H2O is this balanced? 2H2+ O2  2H2O

To know how energy from fuels can be measured. (Grade C) To calculate the energy content of a fuel. (Grade B) To explain how to measure energy changes in solution. (Grade A) Keywords: Fuel, Combustion, Exothermic, Endothermic, Joule, Kilojoule, 2H2+ O2  2H2O

To know how energy from fuels can be measured. (Grade C) To calculate the energy content of a fuel. (Grade B) To explain how to measure energy changes in solution. (Grade A) Keywords: Fuel, Combustion, Exothermic, Endothermic, Joule, Kilojoule, 2H2+ O2  2H2O This reaction is exothermic and so releases energy. This is a reaction (hydrogen being oxidised) that could be an alternative to petrol in cars.

To know how energy from fuels can be measured. (Grade C) To calculate the energy content of a fuel. (Grade B) To explain how to measure energy changes in solution. (Grade A) Keywords: Fuel, Combustion, Exothermic, Endothermic, Joule, Kilojoule, More on Bonds and Reactions

To know how energy from fuels can be measured. (Grade C) To calculate the energy content of a fuel. (Grade B) To explain how to measure energy changes in solution. (Grade A) Keywords: Fuel, Combustion, Exothermic, Endothermic, Joule, Kilojoule, What happens in: N2 + 3H2  2NH3

To know how energy from fuels can be measured. (Grade C) To calculate the energy content of a fuel. (Grade B) To explain how to measure energy changes in solution. (Grade A) Keywords: Fuel, Combustion, Exothermic, Endothermic, Joule, Kilojoule, This is an EXOTHERMIC reaction as more energy released on forming (+96 kJ/Mol) than needed to break the bonds. What happens in: N2 + 3H2  2NH3

To know how energy from fuels can be measured. (Grade C) To calculate the energy content of a fuel. (Grade B) To explain how to measure energy changes in solution. (Grade A) Keywords: Fuel, Combustion, Exothermic, Endothermic, Joule, Kilojoule, Questions: Write balanced symbol equations and calculate the energy changes for the following chemical reactions: Hydrogen + chlorine  hydrogen chloride Hydrogen + oxygen  water

To know how energy from fuels can be measured. (Grade C) To calculate the energy content of a fuel. (Grade B) To explain how to measure energy changes in solution. (Grade A) Keywords: Fuel, Combustion, Exothermic, Endothermic, Joule, Kilojoule, More on Bonds and Reactions

To know how energy from fuels can be measured. (Grade C) To calculate the energy content of a fuel. (Grade B) To explain how to measure energy changes in solution. (Grade A) Keywords: Fuel, Combustion, Exothermic, Endothermic, Joule, Kilojoule, Questions: Write balanced symbol equations and calculate the energy changes for the following chemical reactions: Hydrogen + chlorine  hydrogen chloride ----- H2 + Cl2  HCl (185kJ/mol released) Hydrogen + oxygen  water ------ 2H2 + O2  2H2O (486kJ/mol released)

Energy from Fuels