Chapter 24 Lesson 4 Chemical Reactions and Energy.
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Transcript of Chapter 24 Lesson 4 Chemical Reactions and Energy.
Chapter 24 Lesson 4
Chemical Reactions and Energy
Energy Changes
During a chemical reaction… energy is used to break bonds energy is released when new bonds
are formed
breakingbonds
makingbonds
Chemical Reactions—Energy Exchanges
Dynamic explosion example of a rapid
chemical reaction. Chemical reactions
most proceed more slowly, but all chemical reactions release or absorb energy.
Chemical Reactions—Energy Exchanges
Energy Heat Light Sound electricity.
Chemical bonds the source of this energy
Chemical Reactions—Energy Exchanges
Energy Required chemical reactions ~ some chemical
bonds in the reactants are broken, which requires energy.
Bond formation products produced, new bonds must form. releases energy.
More Energy Out
Exergonic Reactions chemical reactions that release energy less energy is required to break the
original bonds than is released when new bonds form.
Light or heat are given off
Heat Release
Exothermic reaction. energy given off in a
reaction is primarily in the form of heat
burning of wood explosion of dynamite
Exothermic Reaction
reaction that releases energy
energy released by making new bonds outweighs energy req’d to break old bonds
H2(l) + O2(l) H2O(g) + energy reaction that powers the space
shuttle lift-off
More Energy In
Endergonic reactions chemical reaction requiring more energy
to break bonds than is released when new ones are formed
energy absorbed can be in the form of light, heat or electricity
heat must be added.
Heat Absorption
Endothermic reaction energy needed is in the form of heat some can cause water to freeze. barium hydroxide (BaOH)2 and ammonium
chloride (NH4Cl) in water.
Endothermic Reaction
reaction that absorbs energy
energy req’d to break old bonds outweighs energy released by making new bonds
process used to obtain aluminum from aluminum ore
2Al2O3 + energy 4Al + 3O2
Catalysts and Inhibitors
A catalyst substance that speeds up a chemical
reaction without being permanently changed itself
the mass of the product that is formed remains the same, but it will form more rapidly.
Catalysts and Inhibitors
Inhibitors are used to slow down a chemical reaction
Catalysts and inhibitors do not change the amount of product
produced only change the rate of production.