MVHS
Chemistry 2
Mrs. Escalante
Room 712
Name: _______________________________________
ENERGY
Period: _________
Date:_____________
Thermo Unit Introduction
Energy, Heat and Temperature
Powerpoint Notes 1
Read the following paragraph and answer the question :
Energy is measured in many ways. One of the basic measuring blocks is called a Btu. This stands
for British thermal unit and is the amount of heat energy it takes to raise the temperature of one pound of
water by one degree Fahrenheit, at sea level. One Btu equals about one blue-tip kitchen match. One
thousand Btus roughly equals one average candy bar. Energy also can be measured in joules. A thousand
joules is equal to a British thermal unit. The term "joule" is named after an English scientist James
Prescott Joule who discovered that heat is a type of energy. One joule is the amount of energy needed to
lift something weighing one pound to a height of nine inches. So, if you lifted a five-pound sack of sugar
from the floor to the top of a counter (27 inches), you would use about 15 joules of energy. Around the
world, scientists measure energy in joules rather than Btus. Like in the metric system, you can have
kilojoules — "kilo" means 1,000.
1,000 joules = 1 kilojoule = 1 Btu
A piece of buttered toast contains about 315 kilojoules (315,000 joules) of energy. With that
energy you could:
* Jog for 6 minutes
* Walk briskly for 15 minutes
* Sleep for 1-1/2 hours
* Light a 60-watt light bulb for 1-1/2 hours
What is the major way in which we measure energy? ______________________________________
ENERGY : capacity to ________________
or produce ________________________
Two forms of energy:
1. Kinetic - energy due to_________________
2. Potential- energy due to __________________
Chemical Potential Energy- ________________________________
Law of conservation of energy
• The law of conservation of energy states that in _______________________ or physical process, energy
can be ________________________ but it is neither _____________________ nor destroyed.
Example
 A macroscopic example of ________________________is water stored behind a dam above the turbines of
a hydroelectric generating plant.
•
When the dam gates are opened_____________________________________________and does work by turning
____________________to produce __________________________energy.
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MVHS
Chemistry 2
Mrs. Escalante
Room 712
Energy in Chemical Systems
•
•
•
Chemical systems contain __________________________________________energy.
As temperature increases, the motion of particles _____________________
The potential energy of a substance depends upon its _________________________________: the type of a
_________________________________ in the substance, the number and type of _________________________
joining the atoms, and the particular way the atoms are _______________________________
HEAT
Heat (which is represented by the symbol q )is a form of energy that flows from a warmer object to a
cooler object.
•
•
When the warmer object loses heat, its temperature decreases.
When the cooler object absorbs heat, its temperature rises
In the following diagram, circle the arrow that indicates the correct direction of heat flow
70 ° C
10° C

Heat is measured with an instrument called a __________________

The units for measuring heat are _________________ (cal), kilocalories (____________),
_______________________ (J) and kilojoules (______________)

One calorie is the amount of heat needed to raise the temperature of 1 g. of ________by ___________
Relationships Among Energy Units
1J
= 0.2390 cal
1 cal
= 4.184 J
1 kJ
= 1000 J
1 Calorie = 1 kcal (the big calorie is the nutritional calorie , ie. used in food)
1 kcal = 1000 cal
Conversion of Heat/Energy Units (Using Dimensional Analysis)
1. Use the T-chart
2. The number 1 (no unit) goes to the bottom left part of the chart
3. The given (write its unit) goes to the top left of the chart
4. The unit of the number at the bottom right must match that of the given
EXAMPLES
1. Convert 55 cal to joules
55 cal
4.184 J
1
1cal
Answer =
(55) (4.184) = 230.12 J
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MVHS
Chemistry 2
Mrs. Escalante
Room 712
2. Convert 500 joules to calories
500 J
1
1 cal
4.184 J
Answer= 500 ÷ 4.184 = 119.5 cal
PRACTICE PROBLEMS
Convert the following:
1. 300 Joules to calories
2.
Answer : _______________________
4,590 Joules to kiloJoules
Answer:_______________________
3. 0.85 kilojoules to Joules
Answer:_______________________
4. 93 calories to Joules
Answer:_______________________
5. 2.47 kcal to cal
Answer:_______________________
6. 8.56 kJ to cal
Answer:_______________________
TEMPERATURE
What is Temperature?
Wooden block
Metal tray
Woolen Cap
Glass plate
In an experiment, Teddy and Kyle place four objects on a table in the science classroom, and connect
each to a thermometer. They leave these overnight and observe their temperatures the following day at
the same time. Which do you think will occur?
a) none of the objects will have the same temperature
b) two of the objects will have the same temperature
c) three of the objects will have the same temperature
d) all of the objects will have the same temperature
Why?
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MVHS
Chemistry 2
Mrs. Escalante
Room 712
TEMPERATURE
•
•
Measured with a ______________________
Measured in Celsius, (°C), ____________________(°F), or
Kelvin (____)
Conversion of Temperature Units ( Using Formulas)
Celsius-Fahrenheit Conversions: ºF = 1.8 (º C) + 32
Celsius –Kelvin Conversions :
K =ºC
+ 273
EXAMPLES
1. Changing Celsius to Kelvin
Convert 20° C to Kelvins (K)
K = ºC
+ 273
= 20
+ 273
= 293
2. Changing Kelvin to Celsius
Convert 300 K to ° C
K = ºC
+ 273
300 = º C
+ 273
- 273
-273
27 = ° C
3. Changing Celsius to Fahrenheit
Convert 10 º C to °F
ºF = 1.8 (º C) + 32
= 1.8 (10) + 32
= 18 + 32
= 50
4. Changing Fahrenheit to Celsius
Convert 77 °F to ° C
ºF = 1.8 (º C) + 32
77 = 1.8 (º C) + 32
-32
- 32
45 = 1.8 (º C)
Divide by 1.8
45 = 1.8 (º C)
1.8
1.8
25 = ° C
PRACTICE PROBLEMS
Convert the following:
1. 383 kelvins to celsius
Answer : _______________________
2. 110 deg C to Fahrenheit
Answer:_______________________
3. -37 deg C to kelvins
Answer:_______________________
4. 212 deg F to celsius
Answer:_______________________
5. 212 deg F to kelvin
Answer:_______________________
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MVHS
Chemistry 2
Mrs. Escalante
Room 712
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