Section 2.4 Chemical Reactions

Chemical reactions change substances into different substances by breaking and forming bonds.

Chemical reactions are responsible for all the actions of organisms. Examples Photosynthesis Respiration (breathing) Digestion

Metabolism is all the chemical reactions in an organism

Oxygen+Sugars CO2 + Water (Reactants) (Products) Reactants are changed in a reaction EXAMPLE: Products are formed in a reaction Oxygen+Sugars CO2 + Water (Reactants) (Products)

Activation Energy: energy required to start a reaction.

Exothermic Endothermic Two Types of Reactions Energy EXITS! The prefix “exo-” means “out” Example: respiration Energy goes IN! The prefix “Endo” means “into” Example: - photosynthesis

Vocabulary Check Making and breaking chemical bonds are examples of ____________. Bonds are broken in the ______, which are the chemicals that are changed during the process. Bonds are made in the ________, which are the chemicals that result from the process.

Vocabulary Check cont… The ________ is the amount of energy needed to start a reaction. If a reaction absorbs more energy than it releases, it is called an __________ reaction. If a reaction releases more energy than it absorbs, it is called an __________ reaction.

Endo or Exo? 1.

Which is the solute, which is the solvent? 2.

Reactants and Products? 3. 2H2O2 2H2O + O2

4. How are exothermic and endothermic reactions different?

Exothermic or endothermic?

Exothermic or endothermic?

Exothermic or Endothermic?