connecting acids and bases with encapsulation

8/15/2019 Connecting Acids and Bases With Encapsulation

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Connecting Acids and Bases with Encapsulation . . .

and Chemistry with Nanotechnology

Activity Supplement

I. General Teacher Notes

A. Information for the Focus Activity

1. Student Background: Prior to the focus activity !"hat #akes an Acid an Acid . . .$%& students

should have 'een e()osed to certain conce)ts of solution chemistry such as the meaning of

molarity and the difference 'et*een electrolyte and non-electrolyte at the microsco)ic level.

It should 'e noted that Svante Arrhenius originally develo)ed the notion of electrolytes as

charged or ionic su'stances and non-electrolytes as neutral or molecular su'stances.% They *ill

also need to have 'ecome familiar *ith the )ro)erties that cause us to classify a material as an

acid and a 'ase and should have some kno*ledge of e(am)les of these t*o classes of materials.

+. Activity ,'-ective: It should 'e o'vious from the article that the activity set descri'ed is

designed to 'e used as )art of a discussion on acids and 'ases. The goal of the focus activity is

to hel) students gather the same kind of information that lead Arrhenius to his theory of acids

and 'ases *hich *as 'uilt off of his more general Theory of lectrolytes%.

/. #aterials: All materials used in this activity *ere )urchased from 0linn Scientific they are . . .

a. +23*ell reaction )lates 4 AP 1225 6+.78 each

'. 9onductivity testers 4 AP 127/ 617.8 each these have the advantage over other testers of

'eing semi3;uantitative.

c. #agnesium metal 4 #agnesium turnings& #


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*ells in the reaction )late%

2. T*o final notes a'out this activity:

a. It is very im)ortant that the acids 'e used in e(actly the concentrations s)ecified in Part B.

These have 'een determined to )roduce the greatest amount of 'u''le formation for the

different metal 4 acid com'inations *ithout overflo*ing the *ells too greatly.

'. The t*o metal 4 acid com'inations that do not )roduce a )ositive test a @)o) to indicate

hydrogen% *ith the 'urning s)lint are those involving nitric acid. This *as included in the

set 'ecause the activity3set develo)er 'elieves that it is im)ortant that students 'ecome

familiar *ith anomalies 4 instances that do not fit a )attern. In this case& the anomaly is a

result of the fact that it is energetically more favora'le for the nitric acid to )roduce nitrogen

dio(ide than it is too )roduce hydrogen. Students o'serving carefully *ill see evidence for

this in the form of a )roduction of a yello*ish3'ro*n gas in the tu'es for these

com'inations. Teachers concerned *ith the im)act that this *ill have on the a'ility of

students to reach the a))ro)riate conclusion could consider removing these com'inations.

B. Information for the Explore Activity

1. Student Background: This activity is designed to 'uild off of the first one& 'ut it also re;uires at

least a 'asic understanding of the conce)t of ). A lesson to cover this conce)t could 'e

sand*iched 'et*een the focus and e()lore activities. The discussion in this lesson could 'e ke)t

sim)le 'y )resenting ) as the Power of CtheD Hydrogen CIonD& noting that ) is a logarithmic or

)o*er scale similar to the decibel and Richter scales. 0or solutions of sim)le concentrations e.g.

1.< # or 1.< ( 1<3/

#%& students could 'e sho*n that the ) value is e;ual to the negative of the

)o*er of 1< in the molar concentration.

+. Activity ,'-ective: The goal of the reflect )hase is to introduce students to the t*o su'3classes

of acids and 'ases%: *eak and strong. To frame this activity& the teacher might have 'ottles of

the strong la'oratory acids hydrochloric& nitric& and sulfuric% at the front of the room& along *ith


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commercial )roducts containing *eak acids& such as vinegar acetic%& fruit -uices citric%& etc.

/. #aterials:

a. #agnesium metal 4 see information in Section A.

'. #ar'le chi)s 4 0linn Scientific& #


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introductory course due to its im)ortance to not only chemistry 'ut 'iology as *ell.

9. Information for the Reflect Eesson: Teachers are left to their o*n devices as to ho* 'est to

synthesi?e the ideas generated in the focus and e()lore investigations. As noted in the main article&

Folume / of Bassam Shakhashiris Chemical Demonstrations ! Handboo" for #eachers not only

contains some useful demonstrations for getting at some of the conce)ts at hand& 'ut also has some

e(cellent 'ackground information.

J. Information for the !pply Eesson:

1. Student Background: Both as a *ay to revie* the ideas of the )revious lessons and to )rovide the

conte(t for this lesson& the teacher might *ant to 'egin )re3activity discussion 'y reminding

students of the Arrhenius Theory& its main )oints& and ho* those can 'e used to )rovide a

Csim)lifiedD e()lanation of the difference 'et*een *eak and strong acids and 'ases. There *ould

also 'e a need to introduce students to information a'out the )olymer that *ill 'e at the heart of

the *ork they *ill 'e doing references containing such information are found at the end of the

main article 15. and 1.%. It is im)ortant that the teacher discuss the nature of the cross3linked

)olymer shell that students *ill form as they dro) the solutions mi(tures containing alginate into

the calcium chloride solution this *ould offer an o))ortunity to revie* discuss ionic

attractions. Also& it is essential that students have a mental )icture of this )olymer matri( as

something *ith @)ores in it and not as a solid sheet& so that they can understand the diffusion of

various s)ecies and 9,+% that *ill 'e fundamental to understanding their o'servations.

+. Activity ,'-ective: There are t*o goals of this activity. The first is to reinforce students under3

standing of *eak and strong acids and 'ases 'y having them use these conce)ts to account for the

results of their investigation. The second is to introduce them to the )henomenon of enca)sula3

tion so that the teacher can infuse a nanotechnology connection 'y letting students research in

the extension activity% ho* nanoenca)sulated drugs& nanoreactors& gold nanoshells& etc. are 'eing

develo)ed to 'e used in the fight against cancer. These nanoscale strategies hold the )romise of


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more effective treatment of cancers *ithout all of the serious side effects of other methods.

/. #aterials:

a.


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concentration of 1


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in the )revious activity 4 the diffusion of hydrogen ions into the alginate s)heres. It should 'e

discussed *ith them that the reverse )rocess 4 diffusion of chemical s)ecies out of such s)heres 4

can take )lace. This could lead into a discussion of enca)sulation at the micro level and such

a))lications as carbonless copy paper for 'ackground information regarding this& see "hite&

#.A. !The 9hemistry 'ehind 9ar'onless 9o)y Pa)er$& $ournal of Chemical Education& 58& 7&

1117 4 11+


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+. Activity ,'-ective: ,ne of the o'-ectives of this activity is to make students a*are of the

im)ortance of scale in terms of the technological challenges of moving down or up% in scale and

in terms of the effect scale has on a )articular )henomenon. 0or instance& moving from micro3

enca)sulation to nano3enca)sulation re;uired overcoming challenges in the )rocessing involved.

The return for investing the time and money to meet these challenges 4 at least in medical

a))lications 4 is ca)sules that are at the si?e scale and smaller% of the 'iological entities *ith

*hich they are interacting. This has the )otential to make nanoca)sules more effective.

The other goal is to introduce students to the *ide array of nanotechnology3'ased cancer

diagnostic techni;ues treatments 'eing researched at )resent. 0or this reason& the e(tension

activity has a research )resentation format allo*ing each grou) to focus on one )articular

techni;ue treatment& *hile still e()osing the class as a *hole to the entire set of strategies.

/. #aterials: All that is re;uired is access to the Internet for student research.

2. Ans*ers to Muestions in 12.:

a. The 9ongo red has a ) range for its color transition of 3.0 'lue% to 5.2 red%.

'. Both vinegar and sodium 'isulfate are classified as acids. Acetic acid is a wea" acid& *hereas

the bisulfate ion is considered a strong acid. This& of course& im)lies that they *ill 'oth

increase the concentration of /,% in an a;ueous environment as is used in this activity.

c. In 'oth cases& the s)heres *ent through a color change. The s)heres in the vinegar *ill not

change com)letely to 'lue 'ut *ill end u) some intermediate )ur)lish color& *hereas the

sodium 'isulfate s)heres *ill change com)letely to 'lue. In 'oth cases& the color change is

due to the diffusion of

C/,

D into the s)heres.

d. The )ure alginate )roduced no 'u''ling *hile the Gaviscon )roduced 'u''ling. This is due

to the reaction 'et*een /,% diffusing in and 9,/3+ )resent inside the s)heres.

2. 0inal Notes: Some *e' sites for teachers to revie* some are found in the student hand3out%

a. ***.)'s.org*g'hnovascienceno*/+


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the research 4 and gender struggles of Jr. Naomi alas& *ho has )ioneered the use of gold

nanoshells to treat cancer. The 9ancer Nanotech slide sho* )resents an e(cellent overvie* of

different uses of nanotechnology in cancer treatment.

'. ***.cancer.govcancerto)icsunderstandingcancernanodevices 33 A section of the National

Institute of 9ancers *e' site that contains slides on the use of various nanotechnology

)rocesses in the diagnosis treatment of cancer

c. htt):nano.cancer.govresourcecenternanocritical.as) 33 9ontains a discussion of the value

of using nanotechnology to treat cancer as *ell as animations of ho* certain techni;ues *ork

d. ***.livescience.comhuman'iology


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;uantum3dot3introduction.)h) takes you to a series of animations on this to)ic%

II. Student Activity and3out and valuation Ku'rics

Introductory Chemistry Name_____________________________

Activity Set, Investigation 1 ate _____________________________

What Makes an Acid an Acid? (and a Base a Base for That Matter?)

Introduction

Kecent activities and discussions have introduced you to t*o very im)ortant classes of chemicals:

Acids and bases. Rou have 'ecome familiar *ith some of the )ro)erties *hich cause chemists to )lace a

material into one of those t*o classes and 'ecome familiar *ith some common e(am)les. o*ever& for

chemists and for you%& it is not satisfactory to create such categories and to organi?e things into them they

and you% are usually more interested in e()laining *hat causes such categories to e(ist. In this activity&

you *ill 'e a'le to gather the clues necessary to )rovide such an e()lanation for acids and 'ases.

!rocedure

A. "athering Clue #1 a$out Acids

1. ,'tain a +23*ell reaction )late& a *ash 'ottle containing distilled *ater& and a conductivity tester.

+. "orking in Ko* A for this )art& fill each of the first four *ells half *ay *ith distilled *ater.

/. n)ack your conductivity tester 9.T.% and turn it on. Test each of the four distilled *ater sam)les *ith it. If any of them sho* a significant level of conductivity& remove the distilled *ater from the

*ell *ith a )lastic )i)et& clean the *ell out *ith a M3ti)& and then re)lace the distilled *ater in it.

2. Rou and a )artner grou) should share dro))ing 'ottles of the four acids *ith *hich you are going

to *ork in Parts A. and B.: ydrochloric / #% nitric / #% )hos)horic / #% and sulfuric / #%.

Gather u) dro))ing 'ottles containing these four acids read the concentration value carefully%.

8. Add 3 drops of C/ #D hydrochloric acid to the distilled *ater in the *ell 1 of ro* A.& add 3 drops of

C/ #D nitric acid to *ell 2 of ro* A& add 3 drops of C/ #D )hos)horic acid to *ell 3& and add

3 drops of C/ #D sulfuric acid to *ell 4.

=. Place the 9.T. in the li;uid in *ell 1& use the co))er electrodes to mi( in the dro)s of hydrochloric

acid& and then record the conductivity level. Kinse off the electrodes *ith distilled *ater.

5. Ke)eat the )rocess descri'ed in ste) =. for the li;uid mi(tures in the other three *ells.


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. After you have recorded all of your data& turn the 'attery )o*er off on the 9.T.& rinse off the co))er

electrodes one last time *ith distilled *ater& then clean them *ith steel *ool& and 'o( the 9.T. u).

ata

Acid Tested Conductivity Level

1. ydrochloric

+. Nitric

/. Phos)horic

2. Sulfuric

!art A. %ollow&up 'uestions (Show your answers to these to your instructor $e)ore

moving on*

1. "hat is true of the conductivity of the acids you tested and acids in general%L "hat does this tell

you a'out the microsco)ic nature of acid solutionsL i.e. ,f *hat must acid solutions 'e madeL%

+. ,ne of the )ro)erties of all acids is that they taste sour . "hat *ould have to 'e true at the micro3

sco)ic level% of acids to allo* them all to taste the sameL

/. "hat overall conclusion a'out *hat makes an acid an acid can you dra* from Part A.L

B. "athering Clue #+ a$out Acids

1. ,'tain the follo*ing materials: T*o small test tu'es *hich have a mouth si?e *ith the same

diameter as the *ells of your reaction )late& several / 4 2% *ooden s)lints& a cu) of mossy ?inc&

and a cu) of magnesium turnings. The last t*o items can 'e shared *ith your )artner grou).%

+. Rou are going to 'e studying the reaction 'et*een the t*o metals in the materials set zinc and

magnesium% and the four acids that you tested in Part A. ,ne )ro'lem is that three of the four

acids 4 hydrochloric& nitric& and sulfuric 4 re;uire a higher concentration to )roduce a testa'le

amount of gas *ith the ?inc than to )roduce an e;uivalent amount *ith the magnesium. As a

result& you *ill 'e using all 3 M solutions of the acids to react *ith the ?inc& 'ut 1 M solutions of

the acids to react *ith the magnesium e(ce)t for the )hos)horic acid& *hich *ill still 'e 3 M%. To

that end& o'tain dro))ing 'ottles of 1 M hydrochloric& nitric& and sulfuric acids share these%.

/. To make the testing )rocess more clear& a very s)ecific set of directions as to *hat acid solution to

)lace in *hat *ell follo*s. #ake sure that you use the acid straight from the dropping bottle do

not dilute it *ith distilled *ater% and that you fill each *ell half *ay *ith the designated acid . . .

a. ydrochloric: 3 M in ro* A& *ell = and 1 M in ro* B& *ell 8


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'. Nitric: 3 M in ro* B& *ell 1 and 1 M in ro* B& *ell /

c. Phos)horic: 3 M in ro* 9& *ell = and 3 M in ro* J& *ell 8

d. Sulfuric: 3 M in ro* J& *ell 1 and 1 M in ro* J& *ell /

2. Place 1 4 + )ieces of mossy ?inc into the row A& well 6 sam)le of hydrochloric acid and several

a half3do?en% )ieces of magnesium turnings into the row & well 5 sam)le. Immediately cover the *ells containing 'oth of these reaction mi(tures *ith the small test tu'es inverted%.

8. Allo* the reactions occurring in each *ell to )roceed for !1 "inute record o'servations during

that time )eriod. At the end of reaction time& light a *ooden s)lint& lift one of the t*o test tu'es

from its )osition covering the *ell kee) it inverted% and 'ring the burning s)lint to its mouth.

Kecord o'servations and then re)eat this test for the other test tu'e.

=. 9ontinue through the other three )airs of acid sam)les in the manner outlined in ste)s 2. and 8.:

Place mossy ?inc in the 3 M mem'er of the )air& magnesium turnings in the 1 M mem'er& and

cover 'oth reaction *ells *ith test tu'es you can use the same + test tu'es throughout%. After the

13minute reaction time& light a *ooden s)lint& lift the test tu'e off of the *ell and 'ring the burning

s)lint to its mouth. #ake sure to com)are the results of this testing 'et*een the different acids.

5. To clean u)& )ick the )ieces of mossy ?inc out and )lace them in a recovery 'eaker& scra)e the

leftover magnesium into the gar'age can& and rinse the remaining li;uids do*n the sink.

ata a$le

Acid Tested #bservations wit$ %n Metal #bservations wit$ M& Metal

1. ydrochloric

+. Nitric

/. Phos)horic

2. Sulfuric

%ollow&up 'uestions )or !art B.

1. "hat *as the most common results% of the testing you did in this sectionL "hat does this indicate

a'out the gases% )roduced 'y these metal3acid com'inationsL "here did this gas come fromL

+. Jid all of the metal-acid com'inations )roduce the same resultL If not& *hat did you notice that

*as different a'out the ones% that did notL

/. Jra* an overall conclusion: "hy do all acids have the same set of )ro)ertiesL


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C. "athering Clue #1 a$out Bases

1. Rou are 'asically going to re)eat the )rocedure you undertook in Part A.& e(ce)t that you *ill 'e

testing several different bases. To that end& o'tain a clean +23*ell reaction )late and un)ack your

conductivity tester.

&' Ke)eat ste)s +. and /. of Part A.

(' Gather the follo*ing four 'ase solutions: Sodium hydro(ide + #%& )otassium hydro(ide + #%&

sodium car'onate *ashing soda& 1 #%& )otassium car'onate )otash& + #%. Share these *ith your

)artner grou).

)' Add 3 drops of sodium hydro(ide solution to the distilled *ater in *ell 1& 3 drops of )otassium

hydro(ide solution to the distilled *ater in *ell 2& 3 drops of sodium car'onate solution to *ell 3&

and 3 drops of )otassium car'onate solution to *ell 4.

*' Test the conductivity of these li;uid mi(tures as you did in ste)s =. and 5. of Part A.

+' 9lean u) as you did in ste) . of Part A.

. "athering Clue #+ a$out Bases

1. se ro* 9. of your +23*ell reaction )late. Place !15 drops of each of the four 'ase solutions 'eing

studied in a different *ell of this ro* kee) them in the order they a))ear in the Ta'le 'elo*.

+. ,'tain a dro))ing 'ottle of


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Activity Set, Investigation + ate _____________________________

Not All Acids and Bases2 Are Created E3ual

Introduction

"hile most )eo)le have heard of the terms acid and base& fe* )eo)le have a genuine understanding

concerning *hat these terms refer to other than 'eing a'le to identify familiar materials 'elonging to each

category. o)efully& your o*n understanding of that term is no* much dee)er& as you should not only 'e

a'le to )rovide e(am)les of each of those t*o classes of su'stances& 'ut you should also 'e a'le to identify

some of the characteristics 'y *hich *e )lace things in each class. Additionally& you should have achieved

one of the most sought after goals in chemistry: A molecular-le,el e()lanation of why all acids and why all

'ases act alike. That e()lanation is in the form of one the earliest models to account for the 'ehavior of

acids and 'ases: The !rrhenius #heory. It e()lains the )ro)erties of these materials 'y suggesting that

acids are materials that dissociate in *ater to )roduce hydrogen ions CD and 'ases are materials that

dissociate in *ater to )roduce hydro(ide ions C, 33D. This allo*s you to understand the meaning of pH as

the power of hydrogen: The concentration of hydrogen ions in a solution *ritten as its )o*er of ten value.

Rour foray into this to)ic *ill 'e com)lete *hen you are a'le to recogni?e that even though all of

the materials *e call acids share a common set of chemical )ro)erties& there are differences *ithin the

mem'ers of this class of com)ounds that also holds true for 'ases. Though those differences may seem

su'tle on the surface 4 as you may soon discover 4 they have a )rofound im)act in the *ay *e use 4 and

handle 4 different acids and 'ases. Rou *ill ho)efully leave this activity *ith an a))reciation for those

differences 4 and *ith the microsco)ic e()lanation of why those differences e(ist.

!rocedure

1. ,'tain a clean +23*ell reaction )late.

2. Rou *ill need to find 'eakers containing 1 M solutions of the follo*ing four acids: Acetic& citric&

hydrochloric& and nitric. Rou and a )artner grou) can share a set of these acid solutions.% Ans*er

these ;uestions concerning this set of solutions:

a. "hat does the !1 #$ indicateL Be s)ecific.

'. Since all of the solutions in this set are !1 #$& *hat does that mean a'out these four solutionsL

3. Eocate ro* A. of your reaction )late and fill the first *ell in it no "ore t$an one3third of the *ay

*ith the acetic acid solution& the second *ell no more than one3third of the *ay *ith citric acid& the


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third *ell no more than one3third of the *ay *ith hydrochloric acid and the fourth *ell no more

than one3third of the *ay *ith nitric acid.

4. 0ill ro*s B. and 9. in e'actly t$e sa"e "anner as you filled ro* A.

5. Ko* J. *ill 'e filled *ith the same se;uence of acids acetic& citric& hydrochloric& and nitric%

ho*ever& each *ell in this ro* should 'e filled u) appro'i"ately $al( way.

6. ,'tain a cu) containing magnesium metal turnings and an accom)anying scoo)ula. Transfer ) *10

magnesium turnings into the acid CaceticD solution in *ell 1 of ro* A. and o'serve. Ke)eat *ith

the other three *ells in this ro* try to )lace the same num'er of magnesium turnings in each.

Kecord your o'servations in the Jata Ta'le& then ans*er the ;uestions 'elo*:

a. "hat sign)ost of a chemical change is there in these *ellsL

'. "hat su'stance is 'eing )roduced that results in that sign)ost 'eing o'servedL

c. Jid all of the acid sam)les react the same *ayL Should theyL If they didnt& *hy didnt theyL

+. ,'tain a cu) containing marble chips calcium car'onate% and a )air of t*ee?ers. Transfer 1 , 2

mar'le chi)s into the acid CaceticD solution in *ell 1 of ro* B. and o'serve. Ke)eat *ith the other

three *ells in this ro*. Kecord your o'servations in the J. T.& then ans*er the ;uestions 'elo*:

a. "hat sign)ost of a chemical change is there in these *ellsL

'. "hat su'stance is 'eing )roduced that results in that sign)ost 'eing o'servedL

c. Jid all of the acid sam)les react the same *ayL Should theyL If they didnt& *hy didnt theyL

). ,'tain a dro))ing 'ottle containing thymol blue indicator. Add 3 , 5 drops enough to )roduce a

distinct coloration% of this indicator solution to the acid CaceticD in *ell 1 of ro* 9. and o'serve.

Ke)eat *ith the other three *ells in this ro*. Kecord your o'servations in the Jata Ta'le& then

ans*er the ;uestions 'elo*:

a. This is an acid-base or pH indicator *hat is the ) ranges% over *hich this indicator changes

color and *hat are the colors it changes 'et*eenL

'. se the information you -ust filled in for a. to estimate the ) values or the range of values for

each of the four acid solutions. Are the ) values the same for eachL Should they 'eL

-. Set u) a ) Pro'e 4 Ea'Pro System and )roceed through the necessary ste)s to cali'rate this

e;ui)ment to read ) refer to the accom)anying !9ali'rating the ) Pro'e$ hand3out%. Place

the ) )ro'e in the acid CaceticD solution in *ell 1 of J.& then read and record the ) value once


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it sta'ili?es. Kemove the )ro'e from this sam)le& rinse it off thoroughly with distilled water & and

then )lace it in the acid CcitricD solution in *ell +. Kead and record the ) value. Ke)eat for the

other t*o acid Chydrochloric and nitricD solution sam)les. After you have recorded all of the )

values in the Jata Ta'le& ans*er the ;uestions 'elo*:

a. "hat does ) stand forL "hat is 'eing measured 'y the ) valueL

'. Based on the ;uestions you *ere asked in +.& ho* should the ) values of the four solutions

com)are to each otherL ()lain your ans*er.

c. If the four values do not com)are in the manner that you suggest in '.& offer an e()lanation for

*hy they might not.

ata a$le

!roperty ested Acetic Acid Citric Acid 4ydrochloric

Acid

Nitric Acid

1. 56 with 7g

turnings

+. 56 with

mar$le

chips

8. hymol $lue

indicator

9. p4 pro$e

reading

E6perimental Investigations into the Nature o) Acids and Bases

:a$oratory Evaluation 5u$ric

"roup 7em$ers- ________________________ _________________________

________________________ _________________________

5u$ric Element Score Spectrum

1. 9ollected accurate data concerning the conductivity 0 1 2 3 4

of acids in Part A. of the !"hat #akes an Acid& an


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AcidL$ activity

2. 0ormulated a valid conclusion from the results of the 0 1 2 3 4 5

of the cond. testing in that activity

3. 9ollected accurate data concerning the reaction of 0 1 2 3 4

of acids *ith metals in Part B. of the !"hat #akes

an Acid& an AcidL$ activity

4. 0ormulated a valid conclusion from the results of the 0 1 2 3 4 5

of the metal K ( s)lint testing in that activity

5. Kes)onded ade;uately to the ;uestions concerning 0 1 2 3 4

the meaning of 1 M in the !Their Not All 9reated

;ual$ activity

6. 9ollected thorough o'servations and res)onded *ell 0 1 2 3 4

to the ;uestions concerning reactions *ith #g and

9a9,/ in the !Their Not All . . .$ activity

+. 9ollected thorough o'servations and res)onded *ell 0 1 2 3 4

to the ;uestions concerning indicator and ) measure3

ments in the !Their Not All . . .$ activity

). Pro)osed a reasona'le and logically3sound e()lanation 0 1 2 3 4 5

for the result of that activity *hich *as 'ased on

)rior kno*ledge

!oints Achieved- __________

!ossi$le !oints- __________


Activity Set, Investigation 8 ate _____________________________

Encapsulation ; in Chemistry and Beyond

Introduction

It has 'een said that you truly understand something *hen you are a'le to e()lain it clearly to

others. #ost scientists *ould )ro'a'ly say that you truly understand a scientific conce)t *hen you are a'le

to use it to e()lain a ne* instant of that conce)t or to )redict the outcome of a situation that involves that

conce)t. 0or this activity& you *ill 'e held u) to the second vie* of *hat it means to @understand

35Comments-


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something. That something is wea" and strong acids and bases and& in the sim)lest terms& *hat you *ill 'e

asked to do in the investigation that follo*s is to a))ly your understanding of these terms to a model

system. That model system *ill introduce you in a very visi'le *ay to the )henomenon of encapsulation 4

the tra))ing or confining one chemical material in another.

There are e(am)les of enca)sulation all around you: Scratch3n3Sniff stickers& car'onless co)y )a)er

such as *hen you sign a recei)t%& and )ressure3activated adhesives such as Scotch3Gri)U 'y /#%.

Perha)s the most significant of the a))lications of enca)sulation is in the realm of medicine& *here drug

molecules are Cmicro3D enca)sulated so they can survive the -ourney into the digestive system *here they

can 'e released at the a))ro)riate time into the 'lood stream. Taking this )rocess do*n one scale 4 into

nanoencapsulation 4 may give doctors a safer and more efficient *ea)on to use in the *ar on cancer.

9learly& though& 'efore you can understand ho* such a))lications *ork& you first need to see *hat

enca)sulation is and the kind of chemical )rocess associated *ith it. To that end& you *ill study a model

system a sim)le e(am)le that can 'e used to re)resent more com)licated cases. That system *ill involve

forming ca)sules from here on referred to as macrospheres% 'y com'ining a solution of sodium alginate

a commercially useful )olymer o'tained from sea*eed% *ith a solution of calcium chloride. To

a))reciate ho* this formation *ill occur& think of the sodium alginate in the solution as s)aghetti strands

laying on a )late: They are all se)arate from each other assuming you are a good cook% and they are

randomly organi?ed this is *hy the solution is a li;uid. These strands of sodium alginate have carboxyl

grou)s a com'ination of a car'on atom and t*o o(ygen atoms carrying a single negati,e charge% sticking

out of them every so often. "hen you com'ine this solution *ith the calcium chloride solution& calcium

ions Ca2& *ith a double positi,e charge% are a'le to gra' onto car'o(yl grou)s from t*o different

strands and form a @'ridge 'et*een them. This )rocess 4 kno*n as cross-lin"ing 4 )roduces something

akin to a s)iders *e'& *ith the alginate )olymer strands re)resenting the main threads and the calcium3

car'o(yl 'ridges serving as the connecting threads. The

'ottom line is that it organi?es the )olymer strands and

results in the formation of a gel3like material. See the

)icture to the right.

There *ill 'e t*o different sources of the sodium

alginate for creating this model enca)sulated system. ,ne

*ill 'e a solution made of )ure sodium alginate dissolved in

*ater. The other *ill 'e a,iscon& a commercial antacid that

contains sodium alginate as a thic"ening agent %& 'ut also

contains several other chemicals including the t*o active


19/31

ingredients. These t*o sources *ill 'e com)ared they *ill 'e com)ared 'y looking at *hat ha))ens

*hen the macros)heres created from them are transferred from the solution in *hich they are created into

1% vinegar and +% a solution made from the commercial )roduct pH Down *hich is mostly the

com)ound sodium bisulfate and is used to lower the ) of )ool *ater%.

o* *ill you make these com)arisons& thoughL The most im)ortant thing for you to remem'er

going into this investigation is that the sodium alginate and Gaviscon 'oth *ill have had Congo Red

indicator added to them 'y your instructor. The molecules of this indicator *ill 'ecome enca)sulated in

the alginate macros)heres *hen they are formed. ,nce you transfer these macros)heres to the vinegar

and ) Jo*n solutions& the indicator tra))ed in them 4 as *ell as your keen o'servations 4 *ill allo*

you to follo* the course of events. Rour goal *ill 'e to note similarities differences 'et*een *hat

occurs in the vinegar and *hat occurs in the ) Jo*n solution. Eike*ise& you should 'e making

com)arisons 'et*een the )ure alginate s)heres and the Gaviscon s)heres.

As you do *hat *as descri'ed in the )revious )aragra)h& kee) t*o things in mind. 0irst& as *as

stated at the outset of this .ntroduction& this activity is C)artiallyD designed to give you a chance to firm u)

your understanding of ideas related to the chemistry of acids and 'ases. Second& as you )ut your

kno*ledge of acids and 'ases to good use& you should 'e thinking a'out *hat is going on inside and

outside the macros)heres. This *ill 'e an im)ortant first ste) to*ards 'eing a'le to see ho* enca)sula3

tion can 'e used in some many *onderful a))lications.

!rocedure

1. ,'tain a =3*ell reaction )late& a 8$ ( $ inde( card& and a )air of t*ee?ers.

+. 0rom the chemical storage area& o'tain a 'eaker containing 0.3 M calcium chloride CCaCl2D.

/. 9onsult the )icture 'elo* throughout the remainder of this investigation as a reference . . .


20/31

2. Eay your =3*ell K ( )late on the 8$ ( $ inde( card in the orientation sho*n in the dra*ing a'ove.

8. Pour the


21/31

a. "hat is the ) range and color changes% of Congo Red indicatorL

'. "hat do you kno* a'out the chemical nature )ro)erties% of ,inegar L "hat a'out sodium

bisulfate the main ingredient in pH /inus%L "hat is similar a'out themL "hat is differentL

c. "hat *as similar a'out the changes that occurred *hen the alginate Gaviscon macros)heres

*ere transferred to vinegar and *hen they *ere transferred to ) #inusL "hat *as different

a'out the changesL "hat *as ha))ening CchemicallyD to )roduce those changesL

d. "hat *as different a'out *hat ha))ened to the Gaviscon macros)heres com)ared to *hat

ha))ened to the alginate macros)heres *hen they *ere )ut into the t*o different solutionsL

Provide an e()lanation for this. int: Eook at the ingredients list on a 'ottle of Gaviscon.%

18.9lean u) the contents of the reaction )late 'y rinsing them do*n the sink *ith am)le *ater.

ata a$le

Ste) ,'servations Ans*ers to Muestions

=.

5.

.

7.

1


22/31

The ideal *ea)on *ould 'e one that targets only the cancer cells and leaves healthy cells unscathed.

"ith the onset of the +1st century& researchers have 'egun to develo) such *ea)ons. ,ne *ay 'y *hich

such @smart 'om's accom)lish their o'-ective is through the use of encapsulation technologies. In this

a))roach& the chemotherapeutic agent cancer3killing com)ound% is tra))ed inside a s)here. ,n the outside

of the s)here& other molecules are attached that cause the s)here to s)ecifically @stick to only cancer cells.

The s)heres travel through the 'ody& reach the cancer cells& attach themselves to these cells& and then deliver

their deadly )ayload 4 all *ithout affecting near'y healthy cells.

"hy that all sounds sim)le in theory& in )ractice there are tremendous technological challenges to

overcome: o* do you get the drug com)ound inside the s)hereL "hat are the right molecules to attach to

the s)here to ensure that only cancer cells are targetedL and o* can you make sure the drug com)ound

gets )ro)erly released into the cancer cellsL These are ;uestions *ith *hich researchers are and *ill

continue to struggle. They re)resent challenges that *ill likely still 'e around to 'e solved *hen you

graduate from high school and consider a career to )ursue. Perha)s you *ill someday 'e on a team that

acce)ts such a challenge and )roduces the ne(t 'reakthrough in the *ar on cancer.

0irst things first& though: Rou need to learn some 'asic science to 'e a'le to gain some insight into

ho* such strategies *ork and that is the goal of this activity. In sim)le terms& you are going to study the

)rocess of encapsulation 4 the tra))ing of su'stances inside a rigid structure 4 and *hat ha))ens to the

su'stances tra))ed inside *hen the environment around the ca)sule changes. To that end& you are going to

create a model system 4 a sim)le e(am)le that can 'e used to re)resent more com)licated systems 4 to

study. The @shell for that model system *ill 'e )re)ared 'y com'ining a solution of sodium alginate a

)olymer o'tained from sea*eed% *ith a calcium chloride solution. To understand ho* this formation *ill

occur& think of the sodium alginate in the solution as all of the individual fi'ers in a s)iders *e': They are

all se)arate from each other and are randomly organi?ed this is *hy the solution is a li;uid. These strands

of sodium alginate have carboxyl grou)s a com'ination of a car'on atom and t*o o(ygen atoms carrying a

single negati,e charge% sticking out of them every so often.

"hen you com'ine this solution *ith the calcium chloride

solution& calcium ions Ca2& *ith a double positi,e charge%

are a'le to gra' onto car'o(yl grou)s from different strands

and form @'ridges 'et*een them. This )rocess& kno*n as

cross-lin"ing & )roduces connections 'et*een strands& much

as a s)ider strings together the se)arate fi'ers in its *e'. The

'ottom line is that it organi?es the )olymer strands and results

in the formation of a gel3like material. See the )icture to the


23/31

right to give you a molecular vie* of this material.

There *ill 'e t*o different sources of the sodium alginate for creating this model enca)sulated

system. ,ne *ill 'e a solution made of )ure sodium alginate dissolved in *ater. The other *ill 'e

a,iscon& a commercial antacid that contains sodium alginate as a thic"ening agent %& 'ut also contains

several other chemicals including the t*o active ingredients. These t*o sources *ill 'e com)ared.

Another thing that *ill 'e com)ared is ho* the nature of *hat s)ecies are tra))ed in the ca)sules

and the nature of *hat s)ecies are found in the surroundings affect the actions of these ca)sules. To

e()lore this& you *ill tra) either iodine the sim)le molecule 2% or starch a com)le( )olymer structure

'uilt u) from glucose units% in the ca)sules macrospheres% and have the o))osite one in the surroundings.

The )airing of iodine *ith starch forms a com)le( com'ination *ith a distinct )ur)lish3'lack coloration.

,'serving *here that com'ination a))ears *ill )rovide you *ith insights into the

molecular )rocesses that go on inside and outside of the macros)heres. This *ill introduce you to an

im)ortant 'iological )henomenon that occurs in cells. It *ill also 'e the first ste) to*ards understanding

ho* enca)sulation can 'e used in the 'attle against cancer.

!rocedure

1. ,'tain a =3*ell reaction )late& a 8$ ( $ inde( card& and a )air of t*ee?ers.

+. 0rom the chemical storage area& o'tain a 'eaker containing 0.3 M calcium chloride CCaCl2D.

/. 9onsult the )icture 'elo* throughout the remainder of this investigation as a reference . . .


24/31

2. Eay the reaction )late on the 8$ ( $ inde( card in the orientation sho*n in the dra*ing a'ove.

8. Pour the 0.3 M calcium chloride solution into the left3hand3most i.e. first % *ell in each of the t*o

ro*s until the *ell is a'out V of the *ay full.

=. ,'tain a 'eaker of sodium alginate with iodine mi(ed into it. Jra* some of this mi(ture u) into

a )i)et. old the )i)et a fe* centimeters a'ove the surface of the 9a9l+ solution in the *ell in

ro* 1 and 'egin releasing dro)s of the alginate3iodine mi(ture into it. Kelease !10 drops.

Kecord o'servations a'out the s)heres you )roduce. "hat is tra))ed in these s)heresL

0' Ke)eat ste) =. 'ut this time use a 'eaker containing a,iscon with iodine mi(ed into it and

release the dro)s of this mi(ture a'ove the surface of the 9a9l + in the *ell in ro* 2. Again&

record your o'servations. "hat is tra))ed in these s)heresL

1' 0ill the middle *ell in each of the t*o ro*s of your reaction )late a'out V of the *ay *ith *ater.

,'tain a 'eaker of li%uid laundry starch. Jra* some of this sus)ension u) into a )i)et. Kelease

a'out 6 , ) drops of it into each of these t*o *ells& then stir the contents of the *ell to mi( the

starch into the *ater.

2' ,'tain a )air of t*ee?ers. Rou should have noticed the formation of macrospheres in 'oth *ells

as the result of the sodium alginate mi(ing *ith the calcium chloride and going through the

cross3linking )rocess descri'ed in the .ntroduction. se the t*ee?ers to carefully )ick u) the

macros)heres in *ell 1 of ro* 1 formed from the )ure sodium alginate% one at a time and

transfer them into the starch3*ater mi(ture in the middle *ell of ro* 1. "hat is surrounding

these s)heresL #ake o'servations of any immediate changes that occur in this system.

34' Ke)eat the transfer descri'ed in 7. for the macros)heres in *ell 1 of ro* 2 formed from the

Gaviscon%& moving them into the starch3*ater mi(ture in the middle *ell of ro* 2. "hat is

surrounding these s)heresL Again& make o'servations of any immediate changes.

33' Rou are asked to check 'ack on the system in the t*o middle *ells )eriodically as you )roceed

through the ne(t fe* ste)s and to record additional o'servations.

3&' Ke)eat ste) =. a'ove& e(ce)t this time& use a 'eaker containing sodium alginate with starch

mi(ed into it. After you have released !10 drops of this mi(ture into the 9a9l+ solution in *ell

1 of ro* 1& make o'servations of *hat ha))ens. "hat is tra))ed in these s)heresL

3(' Ke)eat ste) 5. a'ove& e(ce)t this time& use a 'eaker containing a,ison with starch mi(ed into

it. After releasing the dro)s into *ell 1 of ro* 2%& make notes. "hat is tra))ed in these s)heresL


25/31

3)' 0ill the right3hand3most ClastD *ell in each of the t*o ro*s of your reaction )late a'out V of the

*ay *ith *ater. ,'tain a 'eaker of iodine either tincture of or raham5s%. Jra* some of this

solution u) into a )i)et. Kelease a'out ) , 10 drops of it into each of these t*o *ells& then stir

the contents of the *ell to mi( the iodine into the *ater.

3*' Kinse off your t*ee?ers from the *ork in ste)s 7. and 1


26/31

1/.

18.

1=.

15.

%ollow&up 'uestions

1. hat is meant $y the term difusion0

+. hy might a chemical species di


27/31

nology hold the )romise of reali?ing this goal.

Rou have already seen the )rinci)le 'ehind one of those develo)ments 4 nanoreactors 4 in the

activity that )receded this )ro-ect. The idea of the *ork that follo*s is to allo* you to learn more a'out

such 'reakthroughs: The )rinci)les 'ehind them& ho* they *ill *ork to kill or diagnose% cancer cells& *hat

their advantages are over the @standard methods radiation and chemothera)y%& and ho* far along the

)rogress is to*ards using them on cancer )atients.

There are numerous *ays in *hich nanotechnology is 'eing 'rought to 'ear on cancer 'oth

diagnosis and treatment%: Nanoreactors mentioned a'ove%& Bucky'alls& nanoshells& ;uantum dots&

dendrimers& and cantilevers to name some of the more im)ortant ones%. It is not )ossi'le for one )erson

or grou) of )ersons to kno* all of the things identified in the )revious )aragra)h a'out all of these different

strategies. As a result& this activity is designed so that each grou) of you *ill )ick one of those strategies&

learn as much a'out it as )ossi'le& and then share your kno*ledge *ith the other grou)s so that they can at

least have a 'asic understanding of it.

The )resentation each grou) *ill give can come in many different forms: It could 'e a )oster&

overhead trans)arencies& Po*erPoint slides& short video )resentation& etc.& etc. se *hatever format 'est

suits the information you gather and your o*n )ersonal talents to decide *hich route to go. In the end&

though& *hatever format you choose& your )resentation needs to 'e 1% clear and concise& +% informative&

/% *ell constructed& and 2% entertaining criteria u)on *hich you *ill 'e evaluated%.

Since you are mem'ers of the @Internet generation& it is assumed that you are ca)a'le of conducting

your o*n research into the strategy your grou) chooses. Kemem'er as you do so to 1% check and dou'le

check% and +% cite your sources. Belo*& you *ill 'e )rovided *ith a cou)le of *e' sites in each of the

various strategy categories -ust to get you started. Rou *ill 'e e()ected& ho*ever& to have more sources of

information than -ust the cou)le of references given to you . . .

1. General Information a'out Nanotechnology in #edicine 9ancer Treatment:

a. ***.cancer.govcancerto)icsunderstandingcancernanodevices

'. ***.)'s.org*g'hnovascienceno*/+


28/31

a. htt):nano.cancer.govresourcecenternanocritical.as)

'. ***.sciencedaily.comreleases+


29/31

3. >sed prior /nowledge o) wea/ and strong acids0 1 2 3 4

5

and $ases to e6plain dised prior /nowledge concerning the properties 0 1 2 34 5

o) acids and $ases to e6plain the $u$$ling

produced in the "aviscon spheres

5. Conducted ade3uate research on the Nanotech 0 1 2 3

4 5

application to cancer to gather su?cient in)o

. !roperly chec/ed and cited the sources used in0 1 2 3 4

5

their Nanotech application to cancer presentation

!. !resentation )ormat was neatly developed and 0 1 2 3

4 5

showed evidence o) ade3uate time devoted to it

". !resentation itsel) was in)ormative and entertaining 0 1 2 3

4 5

!oints Achieved- __________

!ossi$le !oints- __________

Comments-

III. Sam)le Pictures of the A))ly Activity Kesults

A. 0or the 9hemistry Fersion of the Nano3enca)sulation Activity

1. This )icture sho*s the set3u) and materials

used in this activity. In the =3*ell K ( )late&

the t*o left3hand *ells contain


30/31

t*o right3hand *ells are filled *ith sodium

'isulfate C) Jo*nD solution.

+. "hat can 'e seen here are the s)heres )roduced

'y sodium alginate solution left% and 'y the

Gaviscon mi(ture right% after addition to the


31/31

initially u)on 'eing )laced in this solution.

=. The final )icture focuses even further do*n on a cou)le of

the Gaviscon s)heres that have 'een transferred into the

) Jo*n solution. ,ne should 'e a'le to see the C9,+D

'u''les that are 'eginning to 'e released from the s)heres.

connecting acids and bases with encapsulation

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