Transcript Endothermic and Exothermic Reactions

Endothermic and
Exothermic
Reactions
Endothermic
• Endo= ?
in
heat
• Therm = ?
• What does endothermic mean?
• A chemical reaction that needs
energy added to it for the
reaction to take place (energy
is taken IN when it occurs).
Exothermic
• Exo = ?
out
heat
• Therm = ?
• What does exothermic mean?
• A chemical reaction that gives
off energy when the reaction
takes place (energy is EXiting
when it occurs).
Properties of
Endothermic Reactions
• If energy goes IN for the reaction to
occur, would energy be a reactant or a
product?
–Energy is a reactant
• If energy is ABSORBED, would it feel
hot or cold to the touch?
–It would feel cold--it’s absorbing
energy from the surroundings
Properties of
Exothermic Reactions
• If energy EXITS when the reaction
occurs, would energy be a reactant or a
product?
–Energy is a product
• If energy is RELEASED, would it feel
hot or cold to the touch?
–It would feel hot--it releases energy to
the surroundings
Examples of
Endothermic Reactions
• Cold packs
• Evaporation of water
• Melting of ice
Demonstration of
Endothermic Reaction
• NH4Cl(cr) + H2O(l) + energy -->
+
NH4 (aq) + Cl (aq) + H2O(l)
• What are the reactants?
• What are the products?
• What are the states of matter?
Examples of Exothermic
Reactions
• Hot Packs
• Burning coal
• Freezing ice
Demonstration of
Exothermic Reactions
• 2 Al(cr)+ 3CuCl2 (aq) -->
+ energy
3Cu(cr)+ 2AlCl3 (aq)
•
•
•
•
•
What are the reactants?
What are the products?
Can you balance the equation?
What are the states of matter?
Heat pack
Is it Endothermic or Exothermic?
1. When a lit match is placed in alcohol, the
alcohol ignites producing light and heat.
2. Energy in the form of electricity can be
added to water to break apart the water
molecules into hydrogen gas and oxygen
gas.
3. When ammonium chloride mixes with
water, the solution formed feels cold.
4. A piece of wood placed in a furnace
gives off heat and light before turning to
ash.