lhmc
Date
(hsr
Evidence
ofChemical
ftange
Is peanutbrittle nothing but sugarwith peanutsin it? Or doessomethinghappento the sugarduring cooking?When heated,sugarbecomesa light brown syrupto which you canadd peanus.When
cooled,it hardensinto a shiny,brown candy,not into thewhite crystalsthat you startedwith. lf a
friend calledwhile you wereheatingthe sugar,you might comebackto the stoveto find nothing but
a blackmassleft in the pan.Youcan'tgetthe sugarbackfrom the blackmassbecauseit isn't sugarirny
more.It's a differentsubstance
andjust oneexampleof chemicalchangesthat happenaroundyou.
Strategy
Youwill observeand describechemicalreactions.
Youwill identifr signsof chemicalreactions.
Materiars
@ lmF
(SI[gft
plasticspoons(5)
bakingsoda
plasticbag
self-sealing
calciumchloride
plasticmedicinebottle,small
water
papertowel
(2)
50-rnl or 100-mLbeakers
cornstarch
droppers(2)
tinctureof iodine
Epsomsalts
(magnesium
sulfate)
testtubes(2)
washingsoda
(sodiumcarbonate)
petri clishes(2)
dull copperpenny
salt
vinegar
Procedure
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PartA
PartB
l. Put one spoonfulof bakingsodainto the
plasticbag.Usinga secondspoon,put two
spoonfulsof calciumchlorideinto the
bag,and usethat spoonto mlx the substancestogether.
2. Half fill the medicinebottlewith water.Use
a papertowel to wipe off any wateron the
outsideof the bottle.Carefullyplacethe
bottleinto the bagso it remainsupright.
3. Hold the bottle in positionfrom the outsideof the bag.Havea partnerzip the bag,
out asmuch air aspossible.Be
squeezing
surethe bag is tightly sealed.
4. Tip the bagto spill the water into the mixed
chemicals.Hold the bagand observeany
changes.
Recordyour observations
in the
section.
tablein the Dataand Observations
l. Add waterto a bcakeruntil it is abouthalf full.
2. Add two spoonlulsof cornstarchto the
water and stir.
3. Usea dropperto addabout20 dropsof tincture of iodineto the water.Stir it a fewtimes.
WARNING:Iodineispoisonous
if nvallowecl.
Keeltyour handsawnyfrom your ntouth.
4. Allow the beakerto sit for about trvo
minutes.Observewhat happensand record
your observations
in the tablein the Data
and Observations
section.
UnderstandingMatter
13
llane
Date
(hs
PartC
l.
2.
3.
4.
5.
6.
Dissolveone half-spoonfulof Epsomsaltsin a testtube of water.
Dissolveone half-spoonfulof washingsodain anothertesttube of water.
Observewhat the mixtures in both testtubeslook like.
Beginpouring the Epsomsaltsmixure into the petri dish nearone edgeof the dish.
At the oppositeedgeof the petri dish,beginpouringthe washingsodamixture into the dish.
Observewhat happenswherethe two mixturesmeet.Recordyour observationsin the tablein the
Dataand Observationssection.
PartD
l. Placea dull copperpennyin the bottom of a petri dish.
2. Sprinklesaltover the top of the penny.Then usea dropper to coverthe top of the pennywith
vinegar.Observeany changesin the penny.Recordyour observationsin the table in the Data
and Observations
section.
DataandObsenYations
Substances
Ghangesyou observed
Bakingsoda,calcium 1 .
chloride,and water
water,
Cornstarch,
andiodine
2.
Epsomsalts,washing 3.
soda.and water
Copperpenny,salt,
and vinegar
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and(ondusions
Questions
l. ldentifufour signsthat indicatethat a chemicalchangehastakenplace.
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2. In PartA, what evidencedid you observethat a chemicalchangetook place?
3
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3. ln Part B, what evidencedid you observethat a chemical changetook place?
t4 UndcrstandingMatter
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