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Chapter 3 Lecture
Basic Chemistry
Fourth Edition
Chapter 3
Matter and Energy
3.4 Energy
Learning Goal Identify energy as
potential or kinetic; convert between
units of energy.
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Energy
Energy
• is defined as the ability to do work
• can be classified as either kinetic or
potential energy
Kinetic energy is the energy of motion.
Potential energy is determined by the position
of an object or its chemical composition.
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Potential or Kinetic Energy?
Water in a reservoir behind a dam has
potential energy.
When the water is released and flows over the
dam, its potential energy is converted to kinetic
energy.
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Learning Check
Identify the energy in each example as
(1) potential or (2) kinetic.
A.
B.
C.
D.
rollerblading
a peanut butter and jelly sandwich
mowing the lawn
gasoline in the gas tank
© 2014 Pearson Education, Inc.
Solution
Identify the energy in each example as
(1) potential or (2) kinetic.
A. rollerblading
(2) kinetic
B. a peanut butter and jelly sandwich
(1) potential
C. mowing the lawn
(2) kinetic
D. gasoline in the gas tank
(1) potential
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Heat and Units of Energy, Joules
Heat is associated with the motion of particles.
The faster the particles move, the greater the
thermal energy of the substance.
The SI unit of energy is the joule (J).
1 kJ = 1000 J
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Energy Comparison
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Heat and Units of Energy, Calories
The unit calorie is the amount of energy
needed to raise the temperature of 1 g of water
by 1 o C.
• 4.184 Joules (J) = 1 calorie (cal) (exact)
• 1 kilocalorie (kcal) = 1000 calories (cal)
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Learning Check
How many calories are obtained from a pat of
butter if it provides 150 J of energy when
metabolized?
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Solution
How many calories are obtained from a pat of
butter if it provides 150 J of energy when
metabolized?
Step 1 Given 150 J
Need calories
Step 2 Write a plan to convert units.
joules
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Energy
factor
calories
Solution
How many calories are obtained from a pat of
butter if it provides 150 J of energy when
metabolized?
Step 3 State equalities, conversion factors.
1 cal = 4.184 J
© 2014 Pearson Education, Inc.
Solution
How many calories are obtained from a pat of
butter if it provides 150 J of energy when
metabolized?
Step 4 Set up problem and calculate.
© 2014 Pearson Education, Inc.