Academic Chemistry UNIT 2 Matter and THERMOCHEMISTRYstaff.katyisd.org/sites/khschem/Chemistry Documents/Unit 2 Matter... · Academic Chemistry UNIT 2 Matter and ... a swimming pool

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Academic Chemistry UNIT 2

Matter and

THERMOCHEMISTRY

Name:

Class Period: Test Date:

Monday Tuesday Wednesday Thursday Friday

SEPTEMBER 8

9 10 11

Unit 1 TEST

12 Computer Lab: Access Textbook and Energy Activity Pg. 2-3, HW Pg. 4

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 Scientific Notation/Significant Figures Pg 16-18

19 Specific Heat- Pg 19-20

22 More Specific Heat Practice Pg 21-22

23 Hot Seat Activity P.23

24 Test Review Study Guide Pg 24-28

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Unit 2 TEST Thermochemistry

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30 OCTOBER 1

Cumulative Test

2 3

Early Release

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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

2. ____ Potential Energy

3. ____ Thermal Energy

4. ____ Chemical Energy

5. ____ Radiant Energy

6. ____ Electrical 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

http://www.eschooltoday.com/energy/kinds-of-energy/all-about-energy.html

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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?

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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.

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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 Image

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?

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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:

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.

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?

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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:

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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? _______________

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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






Scenario: Bread baking in an oven.

1. System: The bread

2. Surroundings: Air in the oven






“

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Scenario: Water placed into a freezer to make ice cubes

1. System: The freezing water

2. Surroundings: Air in the freezer



5. Is this an endothermic or exothermic process? Why do you think so?



Scenario: A candle burning in a dark room.

1. System: The burning wick







Scenario: Water boiling in a pot on a stove.

1. System: Boiling water







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Name: Period:

Phase Changes Diagram

Label the Phase changes on the diagram:

Period:

Gas

Liquid

Solid

1 2

3 4

1.

2.

3.

4.

5.

6.

5 6

A.

B.

C.

D

E.

b.p./c.p. m.p./f.p.

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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.

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Graph both sets of Data: Include a Key

Temperature VS. Time for the Phase Change of Lauric Acid

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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?

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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

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_______

i. 7.500X108_______ r. 3.92X10-4________

Round the following numbers to 4 sig. figs:

a. 150.98 cm _______ b. 0.0057402 g _______ c. 748.189 ________ d. 0.023475_______

Significant Figures – how many significant figures are in the following?

_____ 1. 4,607,000,000

_____ 2. 0.010006259

_____ 3. 975 x 1010

_____ 4. 0.001256 x 10-14

_____ 5. 15.400

_____ 6. 2010

_____ 7. 100

_____ 8. 9421

Rounding sig figs – round each of these to 3 sig figs:

9) 4,607,000,000 ____________

10) 0.010006259 ____________

11) 154.2549 ____________

12) 0.001256 ____________

13) 0.00459700 ____________

14) 7.092 ____________

15) 1090 ____________

16) 9421 ____________

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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 =

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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) - Cp = specific heat (in J/goC OR cal/goC)

m = mass (in g) - ∆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 = ___________________ Equation:

m = ___________________

∆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.

-Q = Heat is being ________________________________

Solution:

Given:

Cp = ___________________

m = ___________________

∆T = __________________

Unknown:

Equation:

Solution:

Substitute:

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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.

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 ?

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.

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.

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.

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.

Given: Unknown:

Equation:

Solution:

Substitute:

Given: Unknown:

Equation:

Solution:

Substitute:

Given: Unknown:

Equation:

Solution:

Substitute:

Given: Unknown:

Equation:

Solution:

Substitute:

Given: Unknown:

Equation:

Solution:

Substitute:

Given: Unknown:

Equation:

Solution:

Substitute:

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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 = mass X change in Temperature X specific heat (formula) Q = m X ΔT X Cp (variables)

calorie = grams (g) X °C X cal/g°C

(units)

. SPECIFIC HEATS OF COMMON SUBSTANCES

SUBSTANCE Specific Heat

(Joules/g °C) Specific Heat

(calories/g°C )

Copper 0.38 0.09

Gold 0.13 0.03

Lead 0.13 0.03

Water 4.18 1.00

Mercury .140 .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.

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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? _______

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Academic Chemistry Unit 2 Test Review TEST on Thursday 9/25_

1. Describe the following:

a. Thermal Energy:

i. Conduction-

ii. Convection-

iii. Radiation-

b. 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-

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INCREASES / DECREASES / STAYS CONSTANT.

10. During a phase change from solid to liquid, the heat of a substance -


11. During a phase change from gas to liquid, the temperature of a substance -


12. During a phase change from gas to liquid, the heat of a substance -


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?

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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 Specific Heat (Joules/g °C)

Specific Heat (calories/g°C )

Copper 0.38 0.09

Gold 0.13 0.03

Water 4.18 1.00

Mercury 0.140 0.033

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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:

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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)

Temperature Increasing

decreasing Increasing

decreasing

Energy Increasing

decreasing Increasing

decreasing

Feels to the “touch” Cold

Hot cold

hold

System has More energy

Less energy More energy

Less energy

Surroundings have Less energy

More energy More energy

Less energy