Chemistry AS

• enthalpy change is negative
• heat is given out
• making of chemical bonds
• 
• Examples: combustion of fuels (CH₄ + 2O₂ -> CO₂ + 2H₂O), respiration (C₆H₁₂O₆ + 6O₂ -> 6CO₂ + 6H₂O)

• enthalpy change is positive
• heat is taken in
• breaking chemical bonds
• 
• Examples: photosynthesis (6CO₂ + 6H₂0 -> C₆H₁₂O₆ + 6O₂), thermal decomposition (CaCO₃ -> CaO + CO₂)

the energy required to start a reaction by breaking bonds

• Pressure: 100 kPa / 1 atm
• Temperature: 298K / 25^oC

the enthalpy change when one mole of a compound is formed from its constituent elements in their standard states under standard conditions

the enthalpy change when one mole of a substance undergoes complete combustion under standard conditions. All reactants and products are in their standard states

• energy change = mcT
• enthalpy change = -energy change/moles

energy required to break one mole of gaseous bonds to form gaseous atoms

• the enthalpy change is independent of the path taken
• 

• rate increase: more frequent collisions, more successful collisions (increase surface area, increase pressure, increase concentration, increase temperature, use a light source, add a catalyst)
• concentration on rate: increasing concentration increases collisions
• pressure on rate: increasing pressure, particles get closer together, increases frequency of collisions
• temperature on rate: increases temperature, particles get more energy, particle speeds increase