Transcript Exothermic and Endothermic Reactions

Exothermic and Endothermic
Reactions
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Chemical Reactions
• All chemical reactions involve bond
breaking and bond forming.
• Energy is needed to break bonds and
released when bonds are formed.
• Chemical reactions are accompanied by a
change in energy, mainly in the form of
heat.
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Exothermic and Endothermic
Reactions
• A reaction in which heat is given out is
exothermic.
• A reaction in which heat is taken in is
endothermic.
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Endothermic and exothermic reactions
Step 1: Energy must be
SUPPLIED to break
chemical bonds:
Step 2: Energy is RELEASED
when new chemical bonds are
made:
A reaction is EXOTHERMIC if more energy is RELEASED
than SUPPLIED. If more energy is SUPPLIED than is
RELEASED then the reaction is ENDOTHERMIC
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Endothermic process: a
change (e.g. a chemical
reaction) that requires (or
absorbs) heat.
Photosynthesis is an
endothermic reaction
(requires energy input
from sun)
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Forming Na+
and Cl- ions
from NaCl is an
endothermic
process
Measuring Heat
Endothermic
reaction, heat
taken in &
temperature of
the substance
drops
reaction
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EXOTHERMIC & ENDOTHERMIC REACTIONS
Exothermic process: a
change (e.g. a chemical
reaction) that releases
heat.
Burning fossil
fuels is an
exothermic
reaction
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Heat Released
reaction
Exothermic
reaction, heat
given off &
temperature of
substance
rises.
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Examples
Exothermic
Endothermic
• Combustion of fuels
• Yeast & Hydrogen
Peroxide
• Epson salts & water
•
•
Photosynthesis
Acedic Acid &
Sodium Bicarbonate
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