Transcript Chapter 16 - Brookwood High School

Chapter 16
Energy and Chemical Change
Energy
Energy is the ability to do work or produce heat. Can you name some
examples of energy that you observe in your everyday life?
James Prescott Joule was the first person to make the connection between
work and heat which ultimately lead to the Law of Conservation of Energy.
Using a simple machine, Joule was able to calculate the amount of heat
produced by mechanical energy. The amount of heat required for work done
is called the Joule (J). It takes 4.184 joules to move one kilogram one meter in
one second.
Types of Energy
There are 2 different forms of energy : Kinetic and Potential
Potential is due to the composition or position of an object.
Kinetic is energy of motion
Kinetic and Potential Energy
on a Molecular Level
The potential energy is locked in the bonds that hold atoms together in
compounds
The kinetic energy occurs when the chemical bonds separate
Bond Energy
(hehehehehe)
Chemical Potential Energy
The amount of energy stored in a substance. The atoms and type of bond
present in the compound determine the chemical potential energy. In octane
C8H18, the energy is related to the strength found between the carbon and
hydrogen bonds. When the fuel is burned in an engine, the stored energy is
converted to work in moving the pistons which ultimately moves the wheels and
propels the car forward.
Diesel fuel (C12H23) has more Chemical Potential Energy than octane, and as a
result, can achieve the same gas mileage as small economy octane powered
cars.
Law of Conservation of Energy
The Law of Conservation of Energy states that the energy in the universe is
constant. As energy changes from one form to another, there is no net gain or
loss of energy. This explains why perpetual motion machines are a myth. As
machines are set in motion, there is a heat loss due to friction and heat between
mechanical parts and eventually the machine will come to a stop once its energy
has been converted into other forms.
A car engine only converts about 37%
of the energy in gasoline to mechanical
energy to turn the wheels. The other
63% goes to energy in gasoline lost as
heat. All the metal to metal contact in
an internal combustion engine causes
friction.
Measuring Heat
Because energy and heat go hand in hand, the flow of energy and the
resulting change in temperature is measured in the metric system with
joules. Also, a method of measuring heat and energy that is commonly used
is the calorie- the amount of heat needed to raise the temperature of one
gram of pure water one degree centigrade.
Another area the term calorie is used is with food. It takes 1000 calories to
equal one food Calorie.
All of these terms are related and
to satisfactorily complete this
chapter, you will need the following
equivalents memorized:
1000 calories = 1 Calorie = 1 kilocalorie
4.184 joules = 1 calorie
1000 joules = 1 kilojoule
Heat Problems Practice I
1. Convert 10 calories to joules
2. Convert 10 joules to calories
3. Convert 3000 joules to kilojoules
4. Convert 3000 calories to kilocalories
Heat Problems Practice I
5. Convert 3000 calories to Calories
6. Convert 3000 calories to kilojoules
7. Convert 3000 joules to kilocalories
8. Convert 3000 joules to Calories
Heat Problems Practice I
9. Convert 10 kilojoules to kilocalories
10. Convert 10 Calories to kilojoules
11. Convert 3000 calories/minute to joules/hour
12. Convert 10 kilojoules/minute to kilocalories/hour