Academic Chemistry
UNIT 2
Matter and
THERMOCHEMISTRY
Monday
SEPTEMBER 8
Tuesday
9
Wednesday
10
Thursday
11
Unit 1 TEST
15
Heat Vs. Temp.
Pg.5-7
HW- Pg. 8
16
Teacher Demos
Exothermic and
Endothermic
Activity
Pg 9-10
HW- Pg.11
17
Phase Changes/
Diagrams- P.12
LAB: Heats of
Fusion &
Vaporization
Pg 13-15
18
22
23
24
25
More Specific
Heat Practice
Pg 21-22
Hot Seat Activity
Unit 2 TEST
P.23
Test Review
Study Guide
Pg 24-28
29
30
OCTOBER 1
2
19
26
Thermochemistry
Name:
Test Date:
1
12
Computer Lab:
Access Textbook
and Energy
Activity
Pg. 2-3, HW Pg. 4
Scientific
Specific HeatNotation/Significant Pg 19-20
Figures
Pg 16-18
Cumulative
Test
Class Period:
Friday
3
Early Release
Computer Lab Activity: Temperature, Heat, and Types of Energy
Access the online Chemistry textbook by going to the Secondary Portal. Practice accessing the interactive reader.
Then, read pages 509-510.
Define the following:
Thermochemistry: _______________________________________________________________________________
_______________________________________________________________________________________________
Temperature: ___________________________________________________________________________________
______________________________________________________________________________________________
Joule: _________________________________________________________________________________________
Heat: _________________________________________________________________________________________
______________________________________________________________________________________________
Types of Energy
Go to: http://www.eschooltoday.com/energy/kinds-of-energy/all-about-energy.html
Home Page
Scientists define energy as ____________________________________________.
Energy can never be _________________________________________________ (only transformed).
Matching:
1. ____ Kinetic Energy
a. A type of energy that depends on temperature
and mass
b. Energy due to an object’s motion
c. A type of energy transmitted by electromagnetic
waves
d. Energy that depends on electrons moving from
one atom to another
e. A type of energy that depends on the location of
atoms within a molecule
f. Energy due to an object’s position
2. ____ Potential Energy
3. ____ Thermal Energy
4. ____ Chemical Energy
5. ____ Radiant Energy
6. ____ Electrical Energy
2
Thermal (heat) Energy
1. What happens to the movement of molecules as the temperature rises?
2. How does this webpage define thermal energy?
Thermal energy is…
3. Where does heat go when you mix hot tea and cold milk?
4. Are temperature and heat the same thing?
5. What is thermal energy (heat)?
6. Which has more thermal energy (heat): a swimming pool at 40°C or a cup of tea at 90°C? Why?
7. According to that example, what 2 things does heat (thermal energy) depend on?
a. Size
b. Density
c. Texture
d. Temperature
e. Color
8. Of the 2 beakers on the website, which one requires less thermal energy to boil? Why?
9. Draw an image and briefly describe each of the following terms:
a. Conduction
b. Convection
c. Radiation
Chemical Energy
1. What is the definition of chemical energy?
2. When is it released?
3. An exothermic reaction occurs when __________ is a product.
4. In a fire place, where does the chemical energy come from that converts to thermal and light
energies?
5. Why is food a good example of a chemical energy?
3
Homework: Law of Conservation of Energy and Energy Transformations
For the following problems, draw a picture that shows the type and amount of energy that was started with, the
type/types and amount/amounts of energy that you ended with. For some, you may have to do calculations and
identify what one of your final energy types is, but keep in mind that the total amount of energy that you start with
should be EXACTLY the same as the amount you end up with.
1. 10,000 J of light energy is converted to chemical potential energy during photosynthesis.
2. 12,000 J of electricity is run through a hair dryer. Of that, only 500 J is converted to sound energy.
3. 20,000 J of heat energy is released through the burning of methane. One fourth of that energy is converted to
light while the rest is converted to heat.
4.
A car with 25,000 J of kinetic energy crashes to a stop. 18,000 J is converted to mechanical energy, 6,000 J is
converted to heat energy and the rest is converted to sound energy.
5. 100,000 J of electricity is used to fuel a dryer. Two thirds of the energy is used to tumble the clothes (what type
of energy would that be?).
6. 7,500 J of electricity is put into a toaster.
4
Day 2: Heat v Temperature, Energy Transfers
Refreshers:
Kinetic Theory states that all matter is made up of particles that are ______________________________
_________________________ due to heat energy.
Heat travels from a _____________ object to a ____________ object.
a. Heat travels from the ____________ to the ___________________________________.
b. Heat travels from the ____________ to the ___________________________________.
Heat Transfer Review
Type of Heat Transfer
Description
1
electromagnetic waves directly transport
energy through space
2
transfer of energy through matter from particle
to particle
3
transfer of heat by the actual movement of the
warmed matter
But what exactly is heat?
5
Image
The Law of Conservation of Energy states that energy _____________ be
created nor destroyed, but it can be ____________________. So when we
apply heat to something, the energy must be transformed in one of the
following ways:
Self-Check:

Which has a higher
temperature: a match or
an ice sculpture?

Which has more heat
energy: a match or an
ice sculpture? Why?
Phase Changes
Directions: Using red, label the arrows with the appropriate endothermic phase changes and describe
endothermic properties in the left box.
Using blue, label the arrows with the appropriate exothermic phase changes and describe endothermic
properties in the left box.
6
When a substance is heated, the thermal energy can be converted into:
(These are the two “states” of Chemical energy)
________________________is stored energy within a chemical substance.
(If you heat liquid water to the point that it becomes a gas, a portion of the heat energy you apply is required to break
the attractive intermolecular bonds holding the water molecules near one another. In other words, the thermal energy
is transformed into potential energy between the water molecules).
________________________is the energy an object has because of its molecular motion.
(When heating liquid water, a portion of the thermal energy will also become kinetic energy which will results in an
increase in temperature of the substance).
This can be visualized on a heating curve:
7
ASSESSMENT:
1. What is the law of conservation of energy?
2. Which type of reaction absorbs heat from its surroundings, endothermic or exothermic?
3. Label the following as Convection, Conduction, or Radiation:
a. A microwave oven cooking your dinner ___________________________________
b. A metal spoon sits in soup, and the spoon heats up. _________________________
c. Walking across hot sand burns your feet. __________________________________
d. You sit near a campfire. ________________________________________________
e. How a space heater warms an entire room _________________________________
f.
When steam
g. bubbles at the bottom of a boiling pot of water move to the top of the pot
_____________________________________________________________________
4. Which phase of matter has more energy: ____________________________________
5. Which phase of matter has more entropy: ___________________________________
6. If liquid water undergoes an exothermic phase change, what phase will it be in? _____________
7. Is the following a heating or a cooling curve? _________________________________________
Using the graph above, and knowing that the horizontal portions of the graph represent phase changes:
8. At what Celsius temperature does water freeze? _____________
9. At what Celsius temperature does water boil? _______________
8
Endothermic vs. Exothermic
WARM-UP:
 Compare and contrast endothermic and exothermic processes:
Scenario: A glass of iced tea outside on a warm summer day.
1. System: The iced tea
2. Surroundings: Air outside
3. Which has more heat, the system or the surroundings?
4. Is heat flowing into or out from the system?
5. Is this an endothermic or exothermic process?
6. What happens to the kinetic (movement) energy of the particles in the system during this process?
7. How would the temperature of the system feel to you (part of the surroundings) if you touched it?
Scenario: Kevin Garnett's sweaty head during a basketball game.
1. System: Kevin Garnett's head
2. Surroundings: Air in the room
3. Which has more heat, the system or the surroundings?
4. Is heat flowing into or out from the system?
5. Is this an endothermic or exothermic process?
6. What happens to the kinetic (movement) energy of the particles in the system during this process?
7. How would the temperature of the system feel to you (part of the surroundings) if you touched it?
Scenario: Bread baking in an oven.
1. System: The bread
2. Surroundings: Air in the oven
3. Which has more heat, the system or the surroundings?
4. Is heat flowing into or out from the system?
5. Is this an endothermic or exothermic process?
6. What happens to the kinetic (movement) energy of the particles in the system during this process?
7. How would the temperature of the system feel to you (part of the surroundings) if you touched it?
9
Scenario: Water placed into a freezer to make ice cubes
1. System: The freezing water
2. Surroundings: Air in the freezer
3. Which has more heat, the system or the surroundings?
4. Is heat flowing into or out from the system?
5. Is this an endothermic or exothermic process? Why do you think so?
6. What happens to the kinetic (movement) energy of the particles in the system during this process?
7. How would the temperature of the system feel to you (part of the surroundings) if you touched it?
Scenario: A candle burning in a dark room.
1. System: The burning wick
2. Surroundings: Air in the room
3. Which has more heat, the system or the surroundings?
4. Is heat flowing into or out from the system?
5. Is this an endothermic or exothermic process? Why do you think so?
6. What happens to the kinetic (movement) energy of the particles in the system during this process?
7. How would the temperature of the system feel to you (part of the surroundings) if you touched it?
Scenario: Water boiling in a pot on a stove.
1. System: Boiling water
2. Surroundings: Air in the room
3. Which has more heat, the system or the surroundings?
4. Is heat flowing into or out from the system?
5. Is this an endothermic or exothermic process? Why do you think so?
6. What happens to the kinetic (movement) energy of the particles in the system during this process?
7. How would the temperature of the system feel to you (part of the surroundings) if you touched it?
10
11
Name:
Period:
Phase Changes Diagram
Label the Phase changes on the diagram:
1.
Gas
1
2
Liquid
6
5
4
3
2.
3.
4.
5.
6.
Period:
Solid
A.
B.
C.
D
E.
b.p./c.p.
12
m.p./f.p.
Lab: Graphing a Phase Change
WARM-UP:
 Read through the “Principles and Procedures” below.
Materials: Beaker, Ice, Thermometer, heat source, stop watch, safety
goggles, Lauric Acid
Cooling:
1. See Figure 1. Choose a test tube in the hot water bath. Record the temperature, into data table 1, before
removing it from the bath.
2. Remove the test tube from the beaker and place it in the beaker of cool water on your table. Hold the
thermometer in the Lauric Acid so that it does not tough the sides of the test tube, and record the
temperature ever 30 seconds in Data Table 1.
A. Between readings, stir the Lauric acid constantly until it becomes solid.
B. Be sure to note in your data when the liquid Lauric acid first starts to solidify AND when
there is no liquid Lauric acid left.
C. Continue to record the temperature until it drops to 40oC or stops dropping after 2
minutes and all the material is now a solid.
 Note what happens to the volume of liquid Lauric acid as it turns into solid Lauric acid.
D.
Heating:
3. Be sure the beaker of water on the hot plate is still heated. Place the test tube with solid Lauric acid in
the beaker of hot water.
A. Record the temperature of Lauric acid in Data Table 2 as soon as you place it into the hot
water bath.
B. Read and Record the temperature of the Lauric acid every 30 seconds until solid Lauric acid
has changed completely to liquid.
C. When the thermometer is able to move, use it to stir the mixture of solid-liquid Lauric acid.
Continue stirring and recording the temperature every 30 seconds until the temperature of
the sample reaches 60 oC .
 Note in your data when the solid Lauric acid begins to melt AND when it has completely melted.
4. Leave the Lauric acid in the hot water bath
5. Graph all your data on Graph 1. Use one color for the data you obtained while cooling the Lauric acid
and another color for the data you obtained while heating the Lauric acid.
NOTE: Provide a key to indicate what each color represents.
6. Graph all your data on Graph 1. Use one color for the data you obtained while cooling the Lauric acid
and another color for the data you obtained while heating the Lauric acid.
13
Graph both sets of Data: Include a Key
Temperature VS. Time for the Phase Change of Lauric Acid
14
Analysis and Conclusions:
1. At what temperature does Lauric acid become a solid? _____
2. How does this compare to the temperature at which solid Lauric acid becomes a liquid?
3. Describe what occurs in the section on your graph where the line is horizontal.
4. What happened to the volume of Lauric acid as it became a solid?
5. What does this indicate about the density of solid Lauric acid as compared to liquid Lauric acid?
6. As the Laruic acid was melting, heat was being added to it but the temperature did not rise. Where
did the heat energy go?
7. If you used ice instead of Lauric acid in this experiment, how do you think your results/graph would
be different or the same(compare)?
8. If you used twice as much Lauric acid, how would your results compare?
15
16
Rounding Significant Figures





Determine how many significant figures you HAVE?
How many do you WANT?
Circle the significant figure you will be rounding.
Underline the sig fig right after it.
0 – 4 = stays the SAME.
5 – 9 = Rounding UP.
Example: Round 25.052 to 3 significant figures.
________________
Round 25. 052 to 4 sig figs. ______________
Class Practice
Significant Figures – how many significant figures are in the following?
_____ 1.
4,607,000,000
_____ 5.
15.400
_____ 2.
_____ 3.
_____ 4.
0.010006259
_____ 6.
_____ 7.
_____ 8.
2010
975 x 10
10
0.001256 x 10-14
100
9421
Rounding sig figs – round each of these to 3 sig figs:
9)
4,607,000,000 ____________
13)
0.00459700 ____________
10)
0.010006259 ____________
14)
7.092 ____________
11)
154.2549 ____________
15)
1090 ____________
12)
0.001256 ____________
16)
9421 ____________
Try these on your own:
Indicate the number of significant figures for each example.
a. 40.319________
j. 146__________
b. 3.285_________
k. 0.189_________
c. 429.3_________
l. 2873.0________
d. 99.9__________
m. 0.000235______
e. 144__________
n. 2500__________
f. 2500.0_________
o. 1.04X1014_______
g. 3.58X10-9_______
p. 48.57193_______
h. 8365.6_________
q. 0.002300_______
8
i. 7.500X10 _______
r. 3.92X10-4________
Round the following numbers to 4 sig. figs:
a. 150.98 cm _______
b. 0.0057402 g _______
c. 748.189 ________
17
d. 0.023475_______
Carry out the following calculations, expressing your answer in the correct number of significant
figures.
1.
3.55 + 4.8 + 11.6 + 23 =
2. 879.6 - 42.45 =
3.
4.56 X 2.3 X 6.60 =
4. 8560/334.2 =
18
Specific Heat Calculations
WARM-UP:
1. Think about going to the swimming pool and temperature of the water versus the cement or stone
surrounding it. Which of these substances feels hotter in the afternoon? Why do you think this is?
NOTES:
- Specific heat – the amount of heat needed to increase the temperature of a gram of substance by exactly 1°C.
- Water and stone will heat up at different rates because they have different specific heats.
- Which substance has a greater specific heat?
FORMULA: Q = m•Cp•∆T
Q = heat (in J OR cal)
m = mass (in g)
-
Cp = specific heat (in J/goC OR cal/goC)
∆T = change in temperature (in oC)
RULES FOR SOLVING EQUATIONS:
1. Identify and write out the given information.
2. Identify and write out the unknown.
3. Write out the equation or formula you will use.
4. Plug your numbers into the equation and solve.
5. Box your answer. Include units and round your answer to correct significant figures.
GUIDED PRACTICE: Solve the problems below.
Example #1: How much energy is required to raise a 34.0 g sample of copper metal from 20.0 oC to
45.0 oC ? The specific heat of copper is 0.385 J/goC.
Given:
Unknown:
Cp = ___________________
m = ___________________
Equation:
Solution:
∆T = _________________
+Q = Heat is being ________________________________
Example #2: How much heat is released when a 3.20g sample of water is cooled from 83.0 oC to 54.0 oC? The specific
heat of water is 4.18 J/goC.
Substitute:
Given:
Unknown:
Cp = ___________________
m = ___________________
Equation:
∆T = __________________
-Q = Heat is being ________________________________
19
Solution:
PRACTICE PROBLEMS:
1. How many Joules of heat energy are required to raise the temperature of 500.0 g of water from 23.5oC to
75.0oC? The specific heat of water is 4.184 J/goC.
Unknown:
Given:
Substitute:
Equation:
Solution:
2. How much heat energy is needed to change the temperature of a 200.0 g sample of copper by 23.4oC. The
specific heat of copper is 0.3846 J/goC ?
Unknown:
Given:
Substitute:
Equation:
Solution:
3. What amount of heat energy is required to raise the temperature of 35.0 g of lead 40.0oC? The specific heat of
lead is 0.128 J/goC.
Unknown:
Given:
Substitute:
Solution:
Equation:
4. What amount of heat energy is required to change the temperature of 1500 g of water from 70.0oC to 23.0oC?
The specific heat of water is 4.184 J/goC.
Given:
Unknown:
Substitute:
Equation:
Solution:
5. If the expected change in temperature is 76oC, how much heat energy must be added to a 10.0 g sample of
gold? The specific heat of gold is 0.131 J/goC.
Unknown:
Given:
Substitute:
Equation:
Solution:
6. How many Joules of heat energy will be needed to raise the temperature of 1.50 g of alcohol from 45.0oC to
22.0oC? The specific heat of alcohol is 2.14 J/goC.
Unknown:
Given:
Substitute:
Equation:
Solution:
20
More Practice
Significant Figures Practice: How many significant figures are in the following?
1. 150 cm __________
2. 0.005740 g __________
3. 728.0 mL __________
4. 748.189 g __________
5. 0.00234 cm __________
Round the following values to only 2 sig figs. each.
6. 150 cm __________
7. 0.005740 g __________
8. 728.0 mL __________
9. 748.189 g __________
10. 0.00234 cm __________
Directions: To receive full credit, SHOW ALL WORK. Box your final answer with the correct units and Sig
figs.
Heat gained or lost =
Q =
calorie =
mass X change in Temperature X specific heat
m X
ΔT
X
Cp
grams (g) X
°C
X cal/g°C
. SPECIFIC HEATS OF COMMON SUBSTANCES
SUBSTANCE
Specific Heat
(Joules/g °C)
Copper
0.38
Gold
0.13
Lead
0.13
Water
4.18
Mercury
.140
(formula)
(variables)
(units)
Specific Heat
(calories/g°C )
0.09
0.03
0.03
1.00
.033
11. Find the amount of heat, in calories, needed to raise the temperature of .05 g of a substance from 20.0 °C
to 30.0 °C if the specific heat of the substance is 2.01 cal/g °C.
21
12. How much heat, in calories, is needed to raise the temperature of 8.00 g of mercury by 10.00 °C?
13. How much heat, in Joules, is needed to heat 20.0 grams of lead from 20.0°C to 150°C?
14. How much heat, in Joules, is released when a 3.20g sample of water is cooled from 83.0oC to
54.0oC? The specific heat of water is ___________________
HEATING CURVES. Use the heating curve below to answer
the following questions.
15. What is the melting point of the substance? ______oC
16. What is the boiling point of the substance? ______oC
17. Which letter represents heating of the solid?
18. Which letter represents melting of the solid?
19. Which letter represents heating of the gas?
20. Which letter represents boiling of the liquid?
21. Which letter(s) represent PE?
22
_______
23
Academic Chemistry Unit 2 Test Review
TEST on
Thursday 9/25_
1. Describe the following:
a. Thermal Energy:
i. Conductionii. Convectioniii. Radiationb. Chemical Energy:
2. As the temperature of a sample of matter decreases, what happens to the average kinetic energy of the
particles in the sample?
3. What is the law of conservation of energy?
4. When a candle burns, what happens to the heat energy produced by that system?
a. An equal amount of heat was absorbed by the surroundings
b. An equal amount was produced by the universe
c. An equal amount was absorbed by the universe
d. An equal amount was produced by the surroundings
5. Describe the direction of heat flow that occurs as your ice cream melts on the sidewalk.
6. Describe the direction of heat flow that occurs as ice is made in a freezer.
Directions: Circle your answer choices within the following statements. Answer choices are in all CAPS.
7. In an endothermic reaction, heat is ABSORBED / RELEASED by the system. As a result, the system will
have MORE / LESS energy than it did originally and the surroundings will have MORE / LESS energy.
This will cause an endothermic reaction to feel HOT / COLD.
8. In an exothermic reaction, heat is ABSORBED / RELEASED by the system. As a result, the system will have
MORE / LESS energy than it did originally and the surroundings will have MORE / LESS energy. This will
cause an exothermic reaction to feel HOT / COLD.
9. During a phase change from solid to liquid, the temperature of a substance-
24
INCREASES / DECREASES
/ STAYS CONSTANT.
10. During a phase change from solid to liquid, the heat of a substance INCREASES / DECREASES
/ STAYS CONSTANT.
11. During a phase change from gas to liquid, the temperature of a substance INCREASES / DECREASES / STAYS CONSTANT.
12. During a phase change from gas to liquid, the heat of a substance INCREASES / DECREASES / STAYS CONSTANT.
13. Define specific heat:
14. Define calorie:
15. What is the difference between the two previous definitions?
16. A process that absorbs (takes in) heat is called _______________________________.
17. What is larger, one calorie or one joule?
18. Define:
a. Joule:
b. endothermic:
c. exothermic:
19. A Cheeto has 13 Calories (or 13000 calories). If it could be burned, leaving nothing but carbon dioxide and
water, how much heat would be given off?
20. What variable represents specific heat in the formula Q = mCp∆T?
21. What variable represents heat in the formula Q = mCp∆T?
25
Calculate
22. How much heat does it take to warm 37.0g of pure water from 45.0˚C to 67.5˚C if the specific heat of water is
4.18 J/g˚C?
22. How much heat is required to raise the temperature of 250.0 g of mercury from 48.0°C to 100.0°C?
Specific heat of Mercury = 0.140 J/g°C
Is this process endothermic or exothermic? Justify your answer (hint: what is the charge of Q?).
23. Aluminum has a specific heat of _________________ (look it up in your table for #25). How much
heat is lost when a piece of aluminum with a mass of 23.94 g cools from a temperature of 415.0 oC to
a temperature of 22.0 oC?
24. How much heat is required to raise the temperature of 250.0 g of mercury from 48.0°C to 100.0°C?
Specific heat of Mercury = 0.140 J/g°C
Is this process endothermic or exothermic? Justify your answer (hint: what is the charge of Q?).
25. You heat an unknown metal from 30.0°C to 40.0°C. You know it has a mass of 50.0g. What is the
metal, if you determine that it absorbed 190. J of heat in this process?
SUBSTANCE
Copper
Gold
Water
Mercury
Specific Heat
(Joules/g °C)
0.38
0.13
4.18
0.140
Specific Heat
(calories/g°C )
0.09
0.03
1.00
0.033
26
Using the heating curve above, answer the following questions.
25.
Which segments represent an increase in kinetic energy?______________________________
26.
Which segments represent an increase in potential energy?____________________________
27.
Which segments change with temperature?________________________________________
28.
Which segments represent phase changes?_______________________________________
29.
Which segment represents a: Solid?___________ Liquid?_____________ Gas?___________
30.
What is the melting point of this substance?_______________________________________
31.
What is the freezing point of this substance?______________________________________
32.
What is the boiling point of this substance?_______________________________________
33.
What is the condensation point of this substance?___________________________________
34.
Which segment represent both a solid and a liquid?__________________________________
35.
How many minutes did this substance take to melt?__________________________________
36.
Is this the heating curve of water?_______________ Justify your answer:
27
Circle the correct answer for each of the following sources for endothermic reactions and exothermic
reaction:
Source
Endothermic
Exothermic
Heat
Entering (absorbing)
Exiting (released)
Exiting (released)
Entering (absorbing)
Increasing
Increasing
decreasing
decreasing
Increasing
Increasing
decreasing
decreasing
Cold
cold
Hot
hold
More energy
More energy
Less energy
Less energy
Less energy
More energy
More energy
Less energy
Temperature
Energy
Feels to the “touch”
System has
Surroundings have
28