Changes of Mass in chemical reaction and Law of conservation mass
Instructor：Shizuko Hamada
The aim of the workshop
To introduce the point of instruction such as method of experiment to understand the result by accuracy of the
Table balance scale, Modification of usage and the method to reform the table balance scale that is sold
commercially. The visually impaired student can understand the changes of Mass in Chemical reaction through
their own experimentation.
Before starting an experiment.
Usage and improvement of the table balance scale
1. Improvement for confirming the indicator easily by using fingertip.
2. To make the paper counterweight (which is easy to handle) instead of using the plate counterweight.
3. Usage of the table balance scale
・ When handling the counterweight, wash and wipe the hands cleanly.
・ Put the counterweight on the balance from the larger mass (in order to the weight), if the larger
counterweight is heavier than the other side, change to the next lighter counterweight.
・ Remembers the arrangement of the counterweight in the counterweight box and determines the mass by
adding the counterweights that are used.
・ Intheexperiment,examinethechangesbythetablebalancescale,iftheweightchangesbymore
than0.4g,thestudentswillunderstandexactly.
Experiment 1
Does the candle become heavier or become lighter after it is burned?
(compares the mass before and after burning the candle)
1. Cut the cardboard in to a size that can put on the plate of balance. Stick a needle into the center of
paper for making the candle stand and make 2 sets.
2. Stand 2 candles on the candle stands, put on the table balance and make it balance. (photo1)
3. Practice how to ignite the candles. (photo2)
4. Light the candle on one side and put out the fire after 5 minutes. Then investigate the balance.
Photo 1
Photo２
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Experiment 2
Does the paper become heavier or become lighter after the paper is burned?
(compares the mass before and after burning paper)
1. Place the plate (which is made from aluminum foil) on both plates of the table balance.
Place the cardboard under the aluminum foil plate for protecting the plates of the table balance.
2. Put on a match on the braille paper (which is cut in 1/10) on the aluminum foil plate, put the counterweight
on the light side and balance. (Photo 3)
3. Take a match from the plate (which does not add the counterweight) and light it. Then put the match on the
braille paper.
4. After burning out, check the balance and observe appearance.
Figure１
Photo 3
Experiment 3
Does iron burn? Does iron become heavier or become lighter, if iron is burned?
(compares the mass before and after burning steel wood)
1. Place the plate (which made from aluminum foil) on both plates of the table balance.
Place the cardboard under the aluminum foil plate for protecting the plates of the table balance.
2. Put the steel wood 5g on the aluminum foil plate. Put the counterweight on the light side and balance.
3. Light fire on the steel wood (which is on the plate that does not add the counterweight) with a battery.
(Figure 1)
4. After burning out, check the balance and observe appearance.
Experiment 4
Change of mass before and after reaction that can be precipitated.
1. Prepare 2 thin test tubes and 2 thick test tubes, put the diluted sulfuric acid in the thin test tubes and put
Barium Hydroxide solution in the thick test tubes about 1/3 of the test tube.
2. Put the test tubes above (1.) into 2 beakers. (put one thin test tube and one thick test tube as a set in 1
beaker)
3.Place2beakersonthetablebalancescaleandbalance.
4.TakethetesttubesoutfromonesideofbeakerandputSulfuricacidinBariumHydroxidesolution
andobservethechanges.
5. Put the test tubes back into the beaker and investigate the balance.
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Experiment 5 The changes of Mass before/after Gas is generated.
Ⅰ
Using the beaker.
1. Put 2 mo1/L hydrochloric acid of about 30 mL in the beaker.
2. Put the 2g of limestone in the jelly cup and place on the beaker ( no.1) and measure by the table balance
scale. (Photo 4)
3. Put the limestone which is in a jelly cup into the beaker and place the empty jelly cup on the beaker
again. (The beaker is still on the table balance scale)
4.Observetheappearanceinthebeakerandthebalanceofthetablebalancescale
Photo４
Ⅱ
Photo５
Using the plastic bottle.
1. Put the limestone powder (CaCO3) 2 g in the plastic bottle size 500 mL (which is used for Carbonic
acid)
The limestone in Ⅰis difficult to dissolve in a short time, so we use the limestone powder which
dissolves easily.
2. Put 2 mo1/L Hydrochloric acid of about 25 mL into the test tube.
3. Incline the plastic bottle and the test tube and put the test tube into the plastic bottle and close the lid
firmly.
4.Placetheplasticbottleonthetablebalanceandmeasurethemass. Photo5 5.
Inverttheplasticbottleandmakehydrochlorictoreactwiththelimestonepowderwhichisin
thetesttube.Observethechanges. 6.Afterreactionends,placeonthetablebalanceagainandinvestigatethebalance.
7.Afteropeningthelid,placeonthetablebalanceagainandinvestigatethebalance.
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Experiment 6 The relation of the amount that reacts at the chemical changes. (For high school student)
1. Put 2mo1/L Hydrochloric acid of about 30 mL in the beaker.
2. Place the beaker on the table balance and place the film case (that has the limestone powder 2g inside) on
the beaker. After that, measure the whole mass by using the table balance. (Photo 6)
3. Put the limestone powder in the beaker (of which the Hydrochloric is contained) and wait until the
reaction ends.
4. Place the plate on the beaker and place the empty film case on the plate. Measure the mass.
5. Think about the relation between the amount of generated carbon dioxide and the limestone powder.
Photo 6
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