chemical reactions

• Chemical reaction


  The process by which chemical bonds in reactants break to rearrange the same type and number of atoms to make new bonds for the products which may have different properties than the reactants
• Signs a chemical reaction is happening

  • Decrease in temperature (endothermic reaction)
  • Increase in temperature (exothermic reaction)
  • Changing color (displacement reaction)
  • Gives light (combustion of a fuel / flammable)
  • Explosion (combustion of an explosive substance)
  • Bubbles of gas (O2, H2, N2...)
• Neutralisation reaction


  When an acid reacts with an alkali to form a salt (of the acid) + water
• Neutralisation reaction


  • When two substances collide successfully (with the right energy) to form a product
  • This process is irreversible
• Displacement reaction


  AB + C —> AC + B

  C is more reactive

  The more reactive metals will displace the less reactive metals
• Rate of reaction


  The amount (solid) or volume of fluid (gas or liquid) that either decreases in the reactants per minute or is produced / released in the products per minute
• Factors that increase the rate of reaction

  • Increasing the temperature (increases the speed of the molecules: they move faster, collide more often and therefore there will be more successful collisions)
  • Increase the surface area (the molecules of the reactants will meet more often, the greater the surface area)
  • Increasing the concentration of at least one of the reactants when the other one is in excess
  • Using a catalyst (substance, that can be a metal, that speeds up the reaction. They are not used up, you can recycle them and use them again and again)
• Exothermic reaction


  Total energy of reaction = energy making bond - energy breaking bonds <0
• Endothermic reaction


  Total energy of reaction = energy making bond - energy breaking bonds >0
• Synthesis


  A+B --> C
• Decomposition


  A --> B + C
• Displacement


  A + B --> C + D
• Acid-base reaction


  2 reactants, an acid and a base, the acid gives 1 hydrogen to the base. Always H2O
• Redox (oxidation) reaction


  Reactants exchange e-. Mg + Cl2 --> MgCl2
• Neutralisation


  HCl + KOH → KCl + H2O
• Displacement


  Na + Fe NO3 → NaNO3 + Fe
• Displacement


  Cu + AgNO3 → Cu(NO)3 + Ag
• Neutralisation


  H2CO3 + Ca(OH)2 → CaCO3 + 2H2O
• 1. HCl + KOH → KCl + H2O = Neutralisation
  2. Na + Fe NO3 → NaNO3 + Fe = displacement
  3. Cu + AgNO3 → Cu(NO)3 + Ag = displacement
  4. H2CO3 + Ca(OH)2 → CaCO3 + 2H2O = neutralisation