Chemical Reaction Energy
Energy Changes in Chemical
Reactions
• Chemical Potential Energy (PE): the
energy stored in chemical bonds
• Heat, energy that moves from one
object to another - flows from a
warmer object to a cooler object
Reaction Pathway
• Reaction Pathway: Shows the change in
energy during a chemical reaction
Exothermic Reaction
• reaction that
releases
energy
• products have
lower potential energy
than reactants
energy
released
2H2(l) + O2(l)  2H2O(g) + energy
Signs of a Exothermic Reaction
•
•
•
•
•
•
Bright light
Heat
Smoke
Fire
Explosions
Temperature
increases (hotter)
Endothermic Reaction
• reaction that
absorbs
energy
• reactants have
lower potential
energy
than products
energy
absorbed
2Al2O3 + energy  4Al + 3O2
Signs of a Endothermic Reaction
Temperature decrease (gets colder)
FIRE
There are three things
needed for Fire
1. heat
2. fuel
3. oxygen to start /
maintain a fire.
If we take away one of
these three things
the fire burns out
Fire
Word Equation for Fire:
Fuel + oxygen = oxides (and energy)
The chemical reaction for fire is an
Exothermic Reaction
FUELS for fire
• We use a lot of energy
everyday for the
following things:
– Lighting
– Heating
– Cooking
– Entertainment
– Transportation
We get most of this energy
from burning fossil
fuels.
TYPES of FUELS for energy
Fuels are primarily hydrocarbons from two
source:
1. Living material
•
Wood (C6H1206)
2. Fossil Fuels
•
•
•
•
Natural gas (CH4)
Oil
Petrol
butane