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CHEM 30S WRITING ASSIGNMENT: PHYSICAL PROPERTIES OF MATTER

Directions:You are to submit a piece of writing from the perspective of a particle explaining whatlife is like as a particle living among other particles. Your composition must includedescriptive examples from each of the following concepts:

• A minimum of one phase change(melting, freezing, boiling,

• Kinetic energy &condensing, sublimating. or

Temperaturedeposition)

• Intermolecular forces and kinetic

• Densitymolecular theory of gases• Exothermic &

Endothermic ProcessesPurpose:The purpose of this assignment is to give you the opportunity to explain yourunderstanding of some of the physical properties of matter in your own words. Becreative. To help you get started, you may consider one of the following perspectives:• Letter to another particle • News cast

• Cover letter to an employer• Description of a

• Retirement speech

• Political party announcement orcommercial product

or eulogy

election campaign• Diary entry

• Short story

Assessment:You will be marked using the following rubric. You will also have to assess your ownwriting piece and submit your self assessment with the rubric below.

Requirements of the Ph sicall Pro erties of Matter Writin Assi nmentName Period

Criteria Novice (0 -1 point) Intermediate (2 - 3Expert (4 points)

points)

Student Student isinfrequently Student works

demonstrates Little or no evidence independentlycommitment to the of commitment to engaged in the task

during class timetask by following[ the task during class during class time, ,

requesting helpthe timeline andI time, and due dates meets all lbut when necessary andmeeting all due not met assignment due

dates (3) or due

,meets all of the

datesdates not met (2)

assigned due dates

Final product is

Improvement(s) significantlySuperficial

made to the essay improved from the

IStudent improves

E improvements or nowith limited (2) to first draft as a result

the writing piece improvement aremoderate (3) of improvements or

made to the essay first draft is assessedimprovement

:as an exemplary

writing piece

Diffusion

• Vapour

pressure

CHEM 30S WRITING ASSIGNMENT: PHYSICAL PROPERTIES OF MATTER

l

Studentdemonstratescreativity by

selecting a novelmethod of

presenting therequired

information

Student meets thetechnical

requirements ofthe project

*All marks doubledfor this criteriaThe required

topics are correctlydescribed

Self-AssessmentRubric Submitted

with final piece

Student is unable toadopt a suggestedperspective (0) orthe story line does

not follow a logicalsequence (1)

None or only a

single technicalrequirement ispresent in thewriting piece

Few of the requiredconcepts are

described and thosepresent are simplystated and/or many

inconsistenciesevident

No self-assessmentrubric submitted

(0 points)

ntermediate (2 - 3Dints)

Writing piece

incorporates theappropriate

perspective with aclear story line that

is boring (2) ormoderately

engaging (3)

Only 2 or 3technical

requirements aremet

Most of the requiredconcepts are evident

and/or containminor errors in

context or accuracy(3) or concepts aresimply defined (2)without enhancing

the story

Incomplete selfassessment rubric

submitted_ _

(1 point)

Unique writingpiece that captures

and holds thereader's attention

Writing piece iswritten in paragraph

format, does notexceed I double-

sided page, isdouble-spaced andword processed in12 pt. Times New

Roman font

All of the conceptsare evident and are

accurately andartfully described ina way that enhances

the story

Completed self-assessment rubric

submitted(2 points)

/26

Heating Curve of Water Lab

Purpose:Examine the cooling and warming behaviour of water by constructing a heating

curve of temperature versus time, paving special attention to melting point andboiling point temperatures.

Chemicals rind Equipment:• Science Workshop Interface • Ice• Temperature sensor

• 250 mL beaker• Safety goggles

• 100 mL tap water• Hot plate

• Beaker tongs

Safety:Heat and glassware are used in this experiment. Observe appropriate glasswareprecautions. Be careful not to burn yourself or melt the temperature sensor cord on thehot plate while heating the water.

Procedure:Part I: Pre` ar•in the Temperature Sensor and Temperature versus Time Graph

12. Make sure the 500 Interface is turned on. A green light indicates the power is on.Turn on the computer and log on.

13. Double click on the Science Workshop icon on the desktop. Wait for the programto load.

14. Plug the temperature sensor into channel A.15. Open the program HEATCURV.SWS using the Science Workshop program. The

file location is R:1Sharedll_MrDea130S Chem\Heatcurv.sws. Double clicking onthe file will not work.

16. The sensor is now ready to take temperature readings.Part II: Calibrating the Thermometer

6. Obtain all chemicals and equipment.7. Fill a 250 mL beaker with 100 mL of tap water and add 4 ice cubes.8. Press the MON icon in the computer program and use the digital thermometer to

stir the ice-water mixture in the beaker.9. Monitor the temperature as you keep stirring until a plateau is reached.10. Once the plateau is reached, press the STOP icon and double click on the

thermometer icon on the screen right below the black 500 interface box.11. Type 0 as the LOW VALUE and press ENTER and then press OK. Your

thermometer should now read 0°C.Part III: Generating the Heating Curve of Water

12. Press the REC icon. The program should begin to plot the temperature of themixture every 30 seconds.

13. Plug in the hot plate and set the dial to the highest setting. Place the beaker withthe ice-water mixture on the hot plate. If you are sharing a hot plate with anothergroup do not perform this step until both groups have completed up to step 12 orthe beaker may crack.

Heatin g Curve of Water Lab

14. Continue to stir the ice-water mixture as it warms and eventually boils. Monitoryour setup so that you do not burn yourself, melt the cord of the thermometer. orbreak the beaker.

15. Continue monitoring the temperature of the boiling water until 4 successivereadings with a constant temperature are obtained.

16. Empty all liquids into the sink, rinse all glassware and put it and the temperatureprobe away.

IT Save the experiment to your account on the school server.18. Have your teacher check your graph and show you how to properly label it. Print

off one copy of the graph for each member of the group. The program will not letyou print off multiple copies. It is too old, so you will have to print a single copymultiple times. Log off of the computer and return to your seat.

Questions1. What happened to the water temperature during melting?

2. According to your data and graph, what is the freezing temperature of water?

3. I -low does the freezing temperature of water compare to its melting temperature?

4. Tell if the kinetic energy of the water in the test tube increases, decreases, orremains the same in each of these time segments during the experiment,a. When the temperature remains constant in Part 11.

b. When the temperature is changing in Part 11.I.

c. When the temperature remains constant in Part III.

References: Experiment C02: Freezing and Melting of Water. Science WorkshopChemLctr > Lcih.^ with Computers :Teacher `s Guide. 1996. Roseville, CA, p.p. l --- 4.

i--% - 3

CH 30S

Change of State

1. Use the following chart and answer the questions that follow

Substance

Water

Para -dichlorobenzene

Napthalene

Methyl Alcohol .

Mercury

a), What will the state of the following substances be under thefollowing conditions? Solid (s), Liquid (L) or Gas (G) ?

Substance

Condi io -0°C

Room

55 °,c

100 °C

400 °CTemp

Water

Napthalene

Para -dichlorobenzene

Methyl Alcohol

Mercury

b) In what order would Ice, Para and Naptha melt ?

c) In what order would Water, Para and Naptha freeze?

Melting Point Boiling Point

53 °C

0 °C 100 °C

1'74°C

80 °C

-98 °C

-39 °C

F

2. Which of the following has the highest Melting point?a) 0.02 g of Napthab) 2.0 g of Napthac) 20 g of Naptha

3. What would be the freezing point of Mercury and methyl Alcohol?

4. What is the Freezing Point of the following substances?

01

Yo

baC

a y

s w ^a iy

Time+o

+5

ao

Time,(min) (min)

d:

TeinP

O

30to

Time(min)

i 2. 3 4 S

L

' a 1 t0 tl

Time(min)

a) Which of the above could be Para?

b) Why do some graphs have two plateaus?

c) Indicate on each graph where solids, solids and liquids and liquids co-exist. 4

5. A student melted a material using one burner, 130 ml of water as awater bath, 5.00 grams of material and took temperature readingsevery 0.5 minute interval.The data was graphed

Temp,_ -a^

°C56

40

0 2 4 6 8. 10 12 :14 16 18 20E

Indicate on the graph what you would expect to happen if:

a) two burners 'were used?

b) if 10.00.g of material were used'

c) if 1.00 g of material was used?`

d) if x.00 grams of the same material was cooled from 70 °C to 40 °C?

6. Which of the following variables affect the Freezing Point of a substance?

Variable Effect on the Freezing Point

a)

Heat of the burner

b)

Time of cooling

c)

Amount of Material

_Type of Thermometer used

e)

Type of material

f)

Strength of intermolecularbonds

15:5 States of Matter 291

from Celsius to kelvin.

d. -36°

e. -73°

from kelvin to Celsius.

d. 321

e. 894

from Celsius to kelvin.

d. 18°

e. 25°

from kelvin to Celsius.

d. 20

e. 60

6. Convert the following temperatures

a. 65°

b. 16°

c. 48°

Convert the following temperatures

a. 86

b. 191

c. 533


a. 23°

b. 58°

c. -90°


a. 872

b. 690

10. At 25`C,

a. N2

15:5 STATES OF MATTERMatter exists in four states-solid, liquid, gas, and plasma. Thus far,

our discussion of the kinetic theory has been limited to gases. However,kinetic theory can also be used to explain the behavior of solids andliquids. Plasmas are treated as a special case.

Gas particles are independent of each other and move in a straightline. Change of direction occurs only when one particle collides withanother, or when a particle collides with the walls of the container. Gas

particles, then, travel in a completely random manner. Since they traveluntil they collide with a neighbor or with the walls of their container,gases assume the shape and volume of their container.

The particles of a liquid have what appears to be a vibratory type ofmotion. Actually, they are traveling a straight-line path between collisions

near neighbors. The point about which the seeming vibration occursoaten shifts as one particle slips past another, These differences in theamount of space between particles allow the particles to change theirrelative positions continually. Thus, liquids, although they have a definitevolume, assume the shape of their container.

In solids, a particle occupies a relatively fixed position in relation tothe surrounding particles. A particle of a solid appears to vibrate about afixed point. Again, the particle is actually traveling a straight-line pathbetween collisions with very near neighbors. For example, a molecule ofoxygen gas at 25°C travels an average distance equal to 314 times its owndiameter before colliding with another molecule. In a solid, however, theparticles are closely packed and travel a distance equal to only a fractionof their diameters before colliding. Unlike liquids, solids have their par-ticles arranged in a definite pattern. Solids, therefore, have both a definiteshape and a definite volume.

The physical state of a substance at room temperature and standardatmospheric pressure depends mostly on the bonding in the substance.

€. 384

which of the following gas molecules move fastest?

b. F2

C. COj-

d. 02

6. a. 338 Kb. 289 Kc. 321 K

d. 237 Ke. 200 K

7, a. -187°C

d. 48°C

b. V-82"C

e. 621'C

C. 260'C

Four states of matter: solid. liq-uid, gas, plasma.

Gas particles travel in randompaths.

Gases assume the shape andvolume of their container.

Liquid particles travel instraight-line paths between col-lisions, but appear to vibrateabout moving points.

Liquids have definite volumebut assume the shape of theircontainer.

Solid particles appear to vibrateabout fixed points.

Solid particles are arranged in adefinite pattern.

Solids have both definite shapeand definite volume. I

PASCO scientific

0 Chemistry Experiment Library: 06020Science Workshop

C06 Determine Vapor Pressure

Experiment C06: Determination of the Vapor Pressureof a Compound

(Pressure Sensor - Absolute, Temperature Sensor)Concept: phase changeTime: 30 mSW Interface: 300, 500 & 700Macintoshf® file: C06 Determine Vapor PressureWindows® file: C06 VAPO.SWS

Adapted by Tom Russo from MicroChemistry, distributed by Theta Technologies, 203 Bluegrass Ave., Suite174H, South Gate, KY 41071, (606) 441-4768.

EQUIPMENT NEEDED•

Science WorkshopTM Interface•

pressure sensor - absolute

•

temperature sensor•

eyedropper stem (glass part)•

graduated cylinder, 10 mL•

heat source (for the water bath)•

pressure flask or glass bottle, 250 mL•

rubber stopper, two hole (to fit bottle)•

apron and safety gogglesCHEMICALS AND CONSUMABLES•

acetone•

ethanol•

glycerin•

water bath (at 60 C)

PURPOSE

In this laboratory exercise you will investigate the relationship between the temperature andvapor pressure of a liquid.

THEORY

Most substances have characteristic melting and boiling points. The temperature of thesurroundings gives thermal energy to the molecules of matter. Thermal energy causes themolecules to rotate, vibrate and translate. The intermolecular bonds which hold the molecules ofa substance together are strained by an increase in any movement of the molecules. Strongmolecular bonds are more difficult to break and as a result require a higher temperature to causemolecular movement.

The higher the temperature of a liquid, the greater the kinetic energy of the molecules. When themolecules of solid matter absorb enough energy, the substance melts and forms a liquid. When

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C06 - 0

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liquid matter absorbs enough energy, the molecules move with enough speed and momentum tobreak into the vapor or gas phase. As more and more molecules break from the liquid state intothe vapor or gaseous state, the pressure they exert increases. This is the vapor pressure of aliquid. The vapor pressure of all liquids is directly related to the temperature of the liquid.

SAFETY PROCEDURES

Follow all safety directives given by your teacher.

PROCEDURE

For this activity, the temperature sensor measures the temperature of a liquid and the pressuresensor measures the vapor pressure of the liquid. The Science Workshop program records anddisplays the data for both temperature and pressure.

• Start to heat a water bath and maintain the temperature at 60 C. Check the temperatureoccasionally as you set up the rest of the equipment.

PART L Computer Setup

Connect the Science Workshop interface to the computer, turn on the interface, and turn onthe computer.

2. Connect the DIN plug of the temperature sensor into Analog Channel A of the interface.Connect the DIN plug of the pressure sensor into Analog Channel B of the interface.

3. Open the Science Workshop file titled as shown;

Macintosh: C06 Determine Vapor PressureWindows: C06 VAPO.SWS

•

The document will open with a Graph display that has a plot of Temperature in Celsius(deg C) versus Time (min) and a plot of Pressure in kiloPascals (kPa) versus Time.

• Note: For quick reference, see the Experiment Notes window. To bring a display to the top,click on its window or select the name of the display from the list at the end of the Displaymenu. Change the Experiment Setup window by clicking on the "Zoom" box or the Restorebutton in the upper right hand corner of that window.

4. The "Sampling Options..." for this experiment are: Periodic Samples = Fast at 10 Hz.

5. The vertical axis of the temperature plot on the Graph is scaled from 20 to 30 C. Thevertical axis of the pressure plot on the Graph is scaled from 95 to 200 kPa. The horizontalaxis of the Graph is scaled from 0 to 5 minutes.

PART II: Sensor Calibration and Equipment Setup

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C06 -1

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•

You do not need to calibrate the temperature sensor. The temperature sensor produces avoltage that is proportional to temperature (10 mV = 1.0 Celsius). The default calibration is1 1 0.000 C = 1.100 V and -10.000 C = -0.100 V.

You do not need to calibrate the pressure sensor. The pressure sensor produces a voltagethat is proportional to pressure (IV = 100 kPa). The default calibration is 10I kPa equalsapproximately one volt.

1.

Put the barb end of a quick release connector into one end of the piece of plastic tubing thatcomes with the Pressure Sensor.

2.

Fit the top of a 250 mL glass bottle or flask with the two hole rubber stopper. Remove thestopper so that you can work with it separated from the bottle.

3.

Place a drop of glycerin on the bottom end of one hole of the rubber stopper. Insert theglass part of an eyedropper, tip up, into the hole in the stopper. It is necessary to have theglass tip clear the top of the stopper.

4. CAREFULLY fit the tip end of the glass dropper into the open end of the plastic tubing thatcomes with the Pressure Sensor.

5.Align the quick-release connector on one end of the plastic tubing with the connector on thePRESSURE PORT of the Pressure Sensor. Push the connector onto the port, and then turnthe connector clockwise until it clicks (about one-eighth turn).

6.

Place a drop of glycerin in the other hole of the rubber stopper. Slide the temperature sensoras far as you can through the hole in the rubber stopper,

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3Science Workshop

Chemistry Experiment Library: 06020C06 Determine Vapor Pressure

7.

Put 5 mL of acetone in the bottle. Place the bottle into the hot water bath. Leave the bottlein the water bath for four minutes to allow the acetone to vaporize and purge air from theflask.

To interface

Determination of the Vapor Pressure of a Liquid

NOTE: Do not put the rubber stopper into the flask yet.

PART ICI. Data Recording

1.Place the two hole stopper into the top of the flask with the acetone. Remove the flask fromthe water bath. When everything is ready, click on the "REC" button to begin datarecording.

2.

Observe the change in temperature and pressure as the acetone cools.

3.Continue collecting data for about four minutes.

4.Click on the "STOP" button to end data recording.

5.Slowly remove the two hole stopper to allow air to enter the flask.

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C06 Determine Vapor pressure

6. Dispose of the remaining acetone by rinsing the acetone down the drain with a largevolume of water following. Rinse the flask.

7. Repeat the procedure with ethyl alcohol instead of acetone.

ANALYZING THE DATA

I .

To obtain the necessary data from the Graph for the first liquid, acetone, click the "DATA"menu button in the Graph. Select -Run ##1" from the Data menu.

•

Click the "Autoscale" button to rescale the Graph to the data if necessary.

2. In order to determine the relationship between pressure and temperature, change the Graphto show Pressure on the vertical axis versus Temperature on the horizontal axis.

3. Click the "Input" menu button for the vertical axis of the temperature plot of the Graph.

4. Select "Delete Input" from the Input menu for the temperature plot.

5. Click the "Input" menu button for the horizontal axis of the Graph.

6. Select "Analog A, Temp" from the Input menu for the horizontal axis.

•

Click the "Autoscale" button to rescale the Graph to the data if necessary.

7. Repeat the data analysis process for the other liquid.

8. To display the data for ethyl alcohol, click the DATA menu button and select "Run #2"from the data menu.

QUESTIONS

What is the general relationship between the vapor pressure of acetone and the temperatureof the liquid?

2.

Is the relationship linear? Why or why not?

3.

What is the general relationship between the vapor pressure of ethyl alcohol and thetemperature of the liquid?

4.

Is the relationship between acetone and temperature and ethyl alcohol and temperature thesame? How are they different?

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Figure 11.16 Illustration ofthe equilibrium vapor pressureover liquid ethanol. In (a), we

'aginc that no ethanolxules exist in the gas

,jest; there is zero pressure inthe cell. In (b), the rate atwhich molecules of ethanolleave the surface equals therate at which gas moleculespass into the liquid phase.Thus, the rates of condensationand of vaporization are equal.This produces a stable vaporpressure that does not changewith time, as long astemperature remains constant.

Figure 11.17 Distribution ofkinetic energies of surfacemolecules of a hypotheticalliquid compared to theminimum kinetic energyneeded to escape from thestd This minimum enerpdepends on the magnitude ofthe attractive forces betweenmolecules. The fraction ofmolecules having sufficientkinetic energy to escape theliquid is given by the shadedarea.

Liquid ethane[

(a) ]venal

Explaining Vapor Pressure on the Molecular Level

The molecules of a liquid move at various speeds. Figure 11.17 shows the distri-

bution of kinetic energies of the particles at the surface of a liquid at a particular

temperature. The distribution curve is like those shown earlier for gases (Figure

10.13). At any instant, some of the molecules on the surface of the liquid possess

sufficient energy to escape from the attractive forces of their neighbors. The

weaker the attractive forces, the larger the number of molecules that are able

to escape into the gas phase, and hence the higher the vapor pressure.

The movement of molecules from the liquid to the gas phase goes on

continuously. However, as the number of gas-phase molecules increases, the

probability increases that a molecule in the gas phase will strike the liquid

surface and stick there [Figure 11.16(b)]. Eventually, the number of molecules

returning to the liquid exactly equals the number escaping from it. The number

of molecules in the gas phase then reaches a steady value, and the pressure of

the vapor at this stage becomes constant.The condition in which two opposing processes are occurring simulta-

neously at equal rates is called a dynamic equilibrium. A liquid and its vapor are

in equilibrium when evaporation and condensation occur at equal rates. The

observer may conclude that nothing is occurring during an equilibrium, because

there is no net change in the system. In fact, a great deal is happening; molecules

continuously pass from the liquid state to the gas state and from the gas state

to the liquid state. All equilibria between different states of matter possess this

dynamic character. The vapor pressure of a liquid is the pressure exerted by itt

vapor when the liquid and vapor states are In dynamic equilibrium;

F^ Minimum kineticI

energy needed1

to eecc.pie

Kinetic energy

(b) At cqudibriunx

380 Chapter 1 I lntem)olecular Forces, Liquids, and sows

Volatility, Vapor Pressure, and TemperatureWhen vaporization occurs in an open container, as when water evaporates from

a bowl, the vapor spreads away from the liquid. Little, if any, is recaptured atthe surface of the liquid. Equilibrium never occurs, and the vapor continues toform until the liquid evaporates to dryness. Substances with high vapor pressure(such as gasoline) evaporate more quickly than substances with low vapor pres-sure (such as motor oil). Liquids that evaporate readily are said to be volatile.

Hot water evaporates more quickly than cold water because vapor pres-sure increases with temperature. As the temperature of a liquid is increased, themolecules move more energetically and can therefore escape more readily fromtheir neighbors. Figure 11.18 depicts the variation in vapor pressure with tem-perature for four common substances that differ greatly in volatility. Note thatin all cases the vapor pressure increases nonlinearly with increasing temperature.

Vapor Pressure and Boiling Point

A liquid boils when its vapor pressure equals the external pressure acting onthe surface of the liquid. At this point, bubbles of vapor are able to form withinthe interior of the liquid. The temperature of boiling increases with increasingexternal pressure. The boiling point of a liquid at 1 atm pressure is called itsnormal boiling point. From Figure 11.18, we see that the normal boiling pointof water is 100°C.

SAMPLE EXERCISE 11.4Using Figure 11.18, estimate the boiling point of ethanol at 400 mg HgSolution: From Figure 11.18, we we that the boiling point must be about 64°C.

PRACTICE EXERCISEIf we wanted to establish a boiling point of 40°C for diethyl ether, what vapor pressurewould we need to maintain in the container?

Answer: about 960 mm Hg

0 40

60

80 !00

Temperature ("C)

11.5 Vapor Pressure 381

Figure 11.18 Vaporpressure of four commonliquids shown as a function oftemperature. The temperatureat which the vapor pressure is760 mm Hg is the normalboiling point of each liquid.

Vapour Pressure Questions

Use the graph below to answer the following questions.

Vapour Pressures of Acetone and Ethyl Alcohol

Acetone

Ethyl Alcohol

1. What is the vapour pressure of acetone at 36°C?

What is the temperature at which the vapour pressure of ethyl alcohol is 73 kPa?

3. Which substance has the highest vapour pressure below 47°C?

4. If water has the greatest intermolecular forces, where would the vapour pressurecurve of water lie in relation to acetone and ethyl alcohol? A sketch of the vapourpressure of water on the graph is also an acceptable answer.

5. Would water or acetone have the greatest heat of vaporization (d,-,,1,)? (circle one)

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'Ir

Vapour Pressure Questions

6. Which of the three substances would require the greatest amount of energy tovaporize I mole of liquid molecules?

7. Under which conditions of pressure and temperature would both substances

boilsimultaneously?

8. a)

What temperature and pressure conditions are necessary to separate asolution of acetone and ethyl alcohol?

b) Explain how to separate a solution of acetone and ethyl alcohol under theconditions specified in part a).

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Shaftesbury High School, 2240 Grant Ave, Wpg, MB, R3P OP7

4 Evaporation of water also takes place at tem-peratures below 100 'C. If a swimmeremerges from water with 90 g of water cling-

ing to him, (a) why does the swimmer feelcold, even though the day may be hot? (b)How much heat energy is necessary to evap-orate the water clinging to him?

5 An actively sweating person, such as a la-borer or an athlete, on a hot day may loseas much as 3 gallons, or about 11 kg, of waterthrough the skin. (a) How many kilocaloriesare required to evaporate I I kg of water? (b)Explain, in terms of regulating body temper-ature, why sweating is more profuse on hotdays than on cold days.

6 Mercury vapor is a substance which is a cu-mulative poison; that is, repeated small dosesof mercury vapor add up to a seriously dis-abling condition. Explain why, although theboiling point of mercury is 357 'C, it is im-portant to clean up mercury spills thoroughlyand promptly.

7 Carbon tetrachloride is another vapor whichis poisonous. Its boiling point is 76.8 'C. Ex-plain the following: (a) Carbon tetrachloridepoisoning can result from relatively shortexposure to its vapor. (b) Spilled carbon tetra-chloride can be removed from a room bythorough airing, while spilled mercury mustbe cleaned up.

8 Fog is composed of tiny droplets of liquidwater suspended in air. Explain, in terms ofthe relationship between temperature and thevapor pressure of water, why fog is com-monly present during early mornings and lateafternoons rather than at the middle of theday.

9 Refer to Figure 5-6 to answer the followingquestions. (a) What is the normal boilingpoint of each of the substances listed? (b) Ata temperature of 80 °C, which liquids wouldbe boiling? (c) Of all the liquids listed, whichhas the strongest intermolecular forces?

10 A flask containing ethyl alcohol is attachedto a vacuum pump and the pressure is re-duced to 12 min Hg. If the flask is maintainedin an ice-water bath at 0 'C. (a) will thealcohol boil? (b) Which, if any, of the othersubstances listed in Table 5-5 would boil at0 'C if exposed to this same vacuum pump?

11 Atmospheric pressure falls about 25 mm Hgfor every 300 metres above sea level. (a)What would be the boiling temperature ofwater near the top of Pike's Peak, which has

118

an altitude of about 4,300 metres (over 14,000

feet)? (b) Explain why the comforts of a hotcup of tea or soup are difficult for climbersto obtain near the top of Mount Everest(8,839 metres). (c) Suggest a means of ob-taining hot water under such conditions.

12 (a) Explain why food cooks more rapidly ina pressure cooker than in an open pan. (b)Explain why a pressure cooker is more effec-

tive in sterilizing baby bottles and surgicalinstruments than is boiling water in an un-pressurized container.

13 What good reason is there for "pressurizing"automobile cooling systems?

14 Liquid sodium has been proposed as a cool-ant in. nuclear power plants to replace water,

which is used as a coolant in conventionalpower plants. Sodium has a melting point of98 'C and a boiling point of 889 'C. (a)Which would have the higher vapor pressureat 99 °C, sodium or water? (b) Are the inter-molecular forces in sodium stronger orweaker than those in water? How can youtell? (c) Which would you expect to have thehigher heat of vaporization, liquid sodium orliquid water? Why? (d) Which would youpredict to have the higher molar volume inthe gaseous phase at, for instance, 1000 °Cand 1 atm pressure? Why? (Consider smalldifferences carefully.)

15 Butane, a gas used as a fuel in campingequipment, has a melting point of - 138.3 'Cand a boiling point of -0.5 'C. Methane,another common fuel, has a melting point of

-182 °C and a boiling point of -161 'C.Predict whether the following physical prop-erties will be higher or lower for butane thanmethane: (a) intermolecular attraction: (b)heat of vaporization; (c) molar heat of melt-ing; (d) vapor pressure at any given tempera-ture,

16 How much heat must be removed from anice cube tray full of water at 0 'C to freezeit if the tray holds 450 g of water?

17 Explain, in terms of molecular activity, whythe molar heat of vaporization of a substanceis higher than its molar heat of melting.

18 Consider a stoppered flask partially filledwith salt water, in which there is undissolvedsalt at the bottom of the flask even afterseveral days of shaking and swirling. (a) Howmany phases are present in the flask? (b)Describe the components of each phase. (c)Which phases are pure substances and whichare solutions? (d) How could you separate thesolutions into their component pure sub-stances? (e) Would you expect the liquid

19

2C

2:

2,

will have enough kinetic energy (i.e., are moving fast enough) toovercome the forces of attraction in the liquid and escape into thevapor (Figure 5-5). At higher temperatures there will be more mole-cules in the vapor phase. Hence, vapor pressure will increase withtemperature.

TABLE 5-5 VAPOR PRESSURES OF LIQUIDS

Ethy lCarbon

MethylAlcohol

Tetracl3ioride

S icyl emnt' i g)

mm Flg)

( m 4)

82

7.3

15

12

82.220

17 5 :'.

4:3.925

23 8

59.030

31,8

73.8.:5

922 ".

17..

55.3

135.E45

719

.1:'74.0.0 ,

92.5,

222-.2 '.55

I1818,0

'23.676€1.

149.4..

352.765

190 0

448.8 .:70 ..

' 233.7

542 575

289 I

666.1.t3

3551

832.6;'5

433 6

986.7'90

258 1195

633.9

1413"

760.0

1693 3:;

5

Water(mm fig)

46i:<

95

^a6791;;

114:.1431 78,';'216.2317379;451;:

622;724':843:1

9581122

n

1463;

1.41.190;"2.523.413.4

7.639.93

12.8

Benzene(mm Rg)

75

a58

74.94.

118":147182225

271

325

389462547.,;.643753 :"877.

1020

11801360

20

c

Chapter 5 / LIQUIDS and

SOLIDS: CONDENSED PHASES

106

Fig. 5-6 Vapor pressure versustemperature for some commonliquids.

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CFIE30SWorksheet

NAMEDATE

Vapor Pressure and Temperature

1. Using the data in the table below, make a graph of vapor pressure vs temperature on graph

paper. Put temperature on the x-axis and vapor pressure on the y-axis. Connect the data for each

substance with a smooth curve.... Graph. all. three ..suhstances._on the same graph. Include a key to

identify the three curves.

Temperature (°C) of Three Liquids at Different Vapor Pressures

10nun Hg 40 mm H 100 mmH 400 mm H 760 mmmHg

-2.3 19.0 34.9 63.5 78.4

ethanol

-31.1 -9.4 73 39.5 56.5

acetone

-15.9 6.7 25.5 60.8 80.7

cyclohexane

2. Using your graph, determine the following:

a. the vapor pressure of ethanol at 50 °C.

b. the vapor pressure of acetone at 50 °C.

c. the temperature at which the vapor pressure of cyclohexane in 200 mm Hg.

d. the temperature at which the vapor pressure of acetone in 200 mm Hg.

e. which of the substances has the highest vapor pressure.

f. which of the substances has the lowest vapor pressure.

g. which of the substances would evaporate fastest at room temperature.

h. which of the substances would evaporate most slowly at room temperature.

3. Which of the substances has the greatest forces of attraction between molecules? Which has

the smallest? Explain how you know.

4. Which of the substances would require the most energy to evaporate ore-mole of the liquid?

Which would require the least? Explain how you know.

5. Using your graph, predict the temperature at which the vapor pressure of each substance

would be 800 mm Hg.

6. Using your graph, determine the normal boiling temperature of each substance.

7. Using your graph, determine the boiling temperature of each substance at 300 mm Hg.

points) - pbworksshaftesburychemistry.pbworks.com/f/physical+properties+booklet.081.… ·...

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