Download Heat and Energy

Chapter 2
Energy and Matter
2.1
Energy
Copyright © 2005 by Pearson Education, Inc.
Publishing as Benjamin Cummings
1
Learning Goals






Identify energy as potential or kinetic.
Use caloric values to calculate the kilocalories (Cal) in
a food.
Given a temperature, calculate a corresponding
temperature on another scale.
Use specific heat to calculate heat loss or gain,
temperature change, or mass of a sample.
Identify the physical state of a substance as a solid,
liquid, or gas.
Describe the changes of state between solids, liquids,
and gases; calculate the energy involved.
2
Energy
Energy
• makes objects move.
• makes things stop.
• is needed to “do work”.
3
Work
Work is done when
• you climb.
• you lift a bag of
•
•
•
•
groceries.
you ride a bicycle.
you breathe.
your heart pumps blood.
water goes over a dam.
Copyright © 2005 by Pearson Education, Inc.
Publishing as Benjamin Cummings
4
Potential Energy
Potential energy is
energy stored for use at
a later time.
Examples are
•
•
•
water behind a dam.
a compressed spring.
chemical bonds in
gasoline, coal, or food.
Copyright © 2005 by Pearson Education, Inc.
Publishing as Benjamin Cummings
5
Kinetic Energy
Kinetic energy is the
energy of matter in motion.
Examples are
•
•
•
•
swimming.
water flowing over a dam.
working out.
burning gasoline.
Copyright © 2005 by Pearson Education, Inc.
Publishing as Benjamin Cummings
6
Learning Check
Identify the energy as potential or kinetic.
A.
B.
C.
D.
roller blading
a peanut butter and jelly sandwich
mowing the lawn
gasoline in the gas tank
7
Solution
Identify the energy as 1) potential or 2) kinetic.
A.
B.
C.
D.
roller blading (kinetic)
a peanut butter and jelly sandwich (potential)
mowing the lawn (kinetic)
gasoline in the gas tank (potential)
8
Units for Measuring Energy or Heat
Heat is measured in joules or calories.
4.184 Joules (J) = 1 calorie (cal) (exact)
1 kJ = 1000 J
1 kilocalorie (kcal) = 1000 calories (cal)
9
Examples of Energy In Joules
10
Learning Check
How many calories are obtained from a pat of butter
if it provides 150 J of energy when metabolized?
11
Solution
How many calories are obtained is a pat of butter
if it provides 150 J of energy when metabolized?
Given:
Need:
Plan:
Equality:
Set Up:
150 J
calories
J  cal
1 cal = 4.184 J
150 J x 1 cal = 36 cal
4.184 J
12