Science new

• Chemical Reaction


  Involves the formation and breaking of chemical bonds between atoms, resulting in rearrangements of atoms and an accompanying energy change
• Reactants


  Substances that undergo the reaction
• Products


  Resulting substances
• Ways to represent chemical equations


  • Word equations
  • Symbol equations
  • Particle equations
• Word equation


  • Hydrogen Peroxide → Water + Oxygen
• Symbol equation


  • 2H₂O₂ → 2H₂O + O₂
• Collision theory


  Explains how chemical reactions occur and their rates. For a reaction to happen, particles must collide with sufficient energy and in the correct orientation
• Reaction rate


  Depends on the frequency of successful collisions
• How to measure reaction rate


  • Measuring the quantity formed of products over time
  • Measuring the quantity of reactants used over time
• Factors affecting reaction rate


  • Concentration
  • Pressure/Volume (for gases)
  • Agitation (Stirring/Shaking)
  • Temperature
  • Surface Area
  • Catalysts
• Enthalpy


  Represents the total chemical energy within a substance, with changes denoted as ΔH
• Exothermic reactions


  • Release energy to the surroundings, resulting in a negative ΔH
• Endothermic reactions


  • Absorb energy, leading to a positive ΔH
• Enthalpy diagrams


  • Visually represent energy changes, including energy of reactants and products, activation energy, and impact of catalysts on reaction pathways