Download 4 Energy GOB Structures

3.4 Energy
Energy
• makes objects move.
• makes things stop.
• is defined as the ability
to do work.
A defibrillator provides electrical
energy to heart muscle to reestablish normal rhythm.
Learning Goal Identify energy as potential or kinetic;
convert between units of energy.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Kinetic Energy
Kinetic energy is the
energy of motion.
Examples are the
following:
• swimming
• water flowing over
a dam
• working out
The movement of water that flows from the
top of a dam is an example of kinetic energy.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Potential Energy
Potential energy is energy stored for use at a later time.
Examples are the following:
• water at the top of a dam
• a compressed spring
• chemical bonds in gasoline, coal, or food
The water at the top of a dam has potential energy by
virtue of its position. As the water falls over and down the
dam, the potential energy is converted to kinetic energy.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Study Check
Identify the energy in each example as potential or kinetic:
A. rollerblading
B. a peanut butter and jelly sandwich
C. mowing the lawn
D. gasoline in the gas tank
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Solution
Identify the energy in each example as potential or kinetic:
A. rollerblading
kinetic
B. a peanut butter and jelly sandwich potential
C. mowing the lawn
kinetic
D. gasoline in the gas tank
potential
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Heat and Energy
Heat is the energy associated with the movement of particles.
The faster the particles move, the greater the heat or thermal
energy of the substance.
Given an ice cube, as heat is added, the H2O molecules
• that are moving slowly increase their motion.
• eventually have enough energy to change the ice cube
from a solid to a liquid.
Core Chemistry Skill Using Energy Units
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Units of Energy
Energy is measured in
• the SI unit, the joule (J), or in kilojoules (kJ), 1000 joules.
• units of calories (cal) or in kilocalories (kcal), 1000 calories.
The calorie is defined as the amount of energy needed to raise
the temperature of 1 g of water by 1 °C.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Energy Comparison
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Study Check
How many calories are obtained from a pat of butter if it
provides 150 J of energy when metabolized?
A. 0.86 cal
B. 630 cal
C. 36 cal
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Solution
How many calories are obtained from a pat of butter if it
provides 150 J of energy when metabolized?
STEP 1 State given and needed quantities.
ANALYZE
THE PROBLEM
Given
150 J
Need
calories
STEP 2 Write a plan to convert the given unit to the
needed unit.
Energy
joules
calories
Factor
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Solution
How many calories are obtained from a pat of butter if it
provides 150 J of energy when metabolized?
STEP 3 State the equalities and conversion factors.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 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 the problem to calculate the needed
quantity.
×
Answer is C.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.