Download Exothermic vs Endothermic

During a science lab investigating chemical reactions, Mrs.
Gray's students placed an antacid tablet in a zip lock bag.
They recorded the mass of the tablet, 25 grams, and the
bag, 60 grams. Then they carefully added 50 grams of water
and quickly sealed the bag. The tablet began to fizz and
soon disappeared. The bag was filled with gas. If the total
mass of the bag + tablet + water was 135 grams before the
reaction, what was the total mass of the bag + liquid + gas
after the reaction was completed?
60 grams
75 grams
135 grams
270 grams
Exothermic
vs
Endothermic
Exothermic
• Reaction that transfers energy to the
surroundings
• More energy is released when a
bond forms than is used to break
bonds
• Bond energy of the reactants is LESS
than the bond energy of the
products
Exothermic
–Increase in temperature
–Energy is released as heat and light
REACTANTS
PRODUCTS + ENERGY
• Examples:
–Combustion reactions
–Neutralization (acid/base)
–Glow stick/Fireflies
Endothermic
• Reaction that takes in energy from
the surroundings
• More energy is needed to break
bonds in the reactants than needed to
form bonds in the products
• Bond energy of the reactants is
GREATER that the bond energy of the
products
Endothermic
• Surroundings get colder
• Temperature decreases
REACTANTS + ENERGY
PRODUCTS
• Examples
– Photosynthesis
– Energy is stored as endothermic reaction;
released as exothermic reaction
PHOTOSYNTHESIS
6CO2 + 6H2O
C6H12O6
+
6O2
Exo VS Endo
• Occurs in physical processes
(changes) and chemical
reactions
Physical Processes
• Closeness of the particles
• Endothermic: particles go
from close together to far
apart (takes energy)
• Melting, evaporation,
boiling, sublimation
Physical Processes
• Exothermic:
particles go from
far to close (loses
energy)
• Condensation;
freezing