Endothermic & Exothermic

• is energy released or absorbed when atoms break a bond?

  absorbed
• is energy released or absorbed when atoms bond?

  released
• Exothermic reactions release energy, while endothermic reactions absorb energy.
• Thermal energy is required for both exothermic and endothermic reactions
• The enthalpy change (ΔH) is the difference between the final temperature and the starting temperature of a reaction.
• Physical changes are changes that can be seen with the naked eye. they are also reversible.

  there is no new substance.
• Chemical changes are irreversible and energy is absorbed or released and there is a new substance.
• Delta means 'difference' or 'change'
• exo = exit

  endo = into / enter
• when the enthalpy change is (-) , the reaction is exothermic.
• when the enthalpy change is (+) , the reaction is endothermic
• More kinetic energy -> more vibrations -> broken bonds
• Theme bonds are chemical reactions between compounds