Chemical reactions new

• Law of conservation of mass

  Mass can neither be destroyed nor created
• Law of conservation of energy


  Energy can only be transferred and transformed, and it cannot be created or destroyed in a chemical reaction
• In a chemical reaction, the mass of reactants equals the mass of products
• Chemical reactions


  1. Breaking of chemical bonds between reactant atoms

  2. Making of new chemical bonds in the products
• To break bonds, energy must be put into a chemical reaction
• To make bonds, energy is released and absorbed in a reaction
• Energy can be transferred into different forms
• Closed system


  No matter can enter or leave
• Closed system


  • Energy can move through heat/light
  • Artificial in nature
• Open system


  • Matter can enter or leave
  • Energy can still leave (higher rate)
• Open system


  Real world
• Balancing equation


  CaCO3 + H2SO4 → CaSO4 + H2O + CO2
• Calcium Carbonate + Sulfuric acid → Calcium sulfate + Water + Carbon dioxide
• Concentration of reactants


  • More particles in the same space=more collisions
  • If we double the concentration we double the number of collisions
• Temperature


  • Particles turn heat into kinetic energy
  • When they get hotter they move faster
  • When they move faster they collide more often
• Catalysts (enzymes)


  • They reduce the activation energy needed for a reaction
  • They offer alternative route for reaction to take place
  • Less activation energy means more effective reactions
• Too hot denatures enzyme activity
• Decomposition


  Chemical breakdown of a substance into two or more simpler substances
• Death


  The end of life
• Before death - how do we live?

  1. Chemical reactions that sustain organism (metabolism)

  2. Metabolic processes rely on energy

  3. Energy in the form of adenosine triphosphate (ATP), made via cellular respiration
• If cellular respiration can no longer occur

  ATP cannot be made and all metabolism eventually stops
• Disorder of biological functions

  Leads to cell death and decomposition
• Chemical decomposition


  Breaking down of a substance into two or more simpler substances
• Biological decomposition


  Complex molecules (starches, proteins, tissues, organs) break down into more simple molecules, often with the help of microorganisms and enzymes
• Signs of chemical change


  • Change in temperature
  • Odour (smell) produced
  • Colour change
  • Sound produced
  • Gas produced (e.g. methane)
  • Light energy produced
  • Precipitate (solid) produced from solution
• Chemical reactions


  1. Reactants

  2. Products
• Decomposition is the chemical breakdown of a substance into two or more simpler substances
• Time since death


  • 0-9m
  • 24h
  • 16-30m
  • 9
  • 3888800 88
• Stages of decomposition


  • Autolysis-Membranes gets liced, cell breaking
  • Algor mortis - Body losing temperature
  • Pallor mortis - Changing Color-blood goer auray
  • Rigor mortis
  • Liver mortis - Blood down by gravity, purple bruise
  • Bloating (inflating abdomen) - Gases built up
  • Active decay - Maggots Consuming flesh, insects eating
  • Skeletinization - everything gets Chewed
• Reaction Rates
• Cur exceptio
• Factors affecting rate of body decomposition


  • Enviromental temperature-cold, slower, hot, faster
  • Avalibility of oxygen
  • Humidity of wetness - dry makes decomp slower, wet allows microorganisms to move faster and freer
  • Rainfall - really wet = slows down, no exposure to oxygen
  • Body size and weight - Faster if Gigger, bacteria has more room to grow
  • Food or objects in body's digositive tract - Yogurt fosters a lot of bacteria
  • Clothing - influences hedy temp compared to Enviroment
  • Surface = eg. Snow or mud or concrete
  • Cause of death- eg. Stabbet, vacteria exposed fam Trauma, including wounds and crushing blows
  • Burial, depth of Larial and soil type
  • Access by Scavengers