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
• Reactants are
changed in a
reaction
• EXAMPLE:
• Oxygen+Sugars
(Reactants)
• Products are
formed in a
reaction
CO2 + Water
(Products)
Activation Energy: energy required to start
a reaction.
Two Types of Reactions
Exothermic
• Energy EXITS!
• The prefix “exo-”
means “out”
• Example:
– respiration
Endothermic
•
•
•
Energy goes IN!
The prefix “Endo”
means “into”
Example:
- photosynthesis
Vocabulary Check
1. Making and breaking chemical bonds
are examples of ____________.
2. Bonds are broken in the ______, which
are the chemicals that are changed
during the process.
3. Bonds are made in the ________,
which are the chemicals that result
from the process.
Vocabulary Check cont…
1. The ________ is the amount of energy
needed to start a reaction.
2. If a reaction absorbs more energy than
it releases, it is called an __________
reaction.
3. 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?