Physical Science 
Experiment 9 
Testing Antacids 


Hello.  Welcome back.  


Today's experiment places you in the 
position of testing truth in advertising.  


I'm sure you've seen on television 
a number of different commercials 


where one product or another is claimed to 
be better or even best for a certain function.  



Well, exactly what does that mean when we say better and best?  Better than what?  And best for what?  



In today's experiment we're going to be looking at antacid tablets which you probably know are taken for upset stomach.  



In your stomach there's acid and it's there for 
a purpose, it's to help you digest your food. 


But too much acid of course causes problems and at that point people often take an antacid tablet.  


Antacids in general are bases or 
hydroxides, the opposite of acids.  


On a pH scale, very acidic solutions form a pH of 0 or 1 and very basic solutions have a pH of of 13 or 14.  


Right in the middle, the number 7, indicates neutrality.  


And when we take an acid and a base 
and put them together properly, 


they neuralize, giving us a solution with a pH of 7.  In this experiment that you're going to do today 


you're going to create artificial stomaches using glass flasks and pour into each one some acid.  



Then you're going to add to each one an antacid tablet.  



We'll use four different ones to find out which 
one really does the best job at reducing acidity.  


The idea is that we put in a lot of 
acid and then add our antacid tablet.  


The tablet won't neutralize all of the acid so we add additional base or sodium hydroxide to the solution, 


aiming for the end point of neutrality or pH 7.  



We can see then that adding the extra base or the extra hydroxide is a measure of relative effectiveness.  



If our antacid tablet does a good job of neutrallizing the acid then we won't need very much extra sodium hydroxide.  


A tablet which is not very effective 
will require us to add a lot more 



and if you look at the chart in your 
instructions, you'll see exactly that.  



That when we have our bar graph 
that we'll make at the end, 


the one tablet that has the least amount of extra sodium hydroxide added is the most effective.  


That's the basic idea behind the experiment.  



We want to find out which tablet really 
does neutralize stomach acid the best.  


Let's have a look at some of our equipment.  



Naturally we've got a whole string of chemicals 
here and our various antacid tablets.  


We'll be using artificial flasks.  
These will be our stomachs.  



These are Erlenmeyer flasks and these create artificial stomachs for us.  We'll be adding acid to these.  



But the heart of the experiment is our 
titration apparatus, and that's here.  


It's delicate. It's fragile. You really 
want to be careful when you use this.  


We'll be filling up the device with sodium hydroxide 


and through a valve at the bottom we'll be 
releasing the hydroxide into our flasks.  


The base of this is an automatic stirrer and 
I'll show you how that works in a few minutes.  


But I think we're ready now to begin.  


We want to remember now that working in 
the laboratory is a little bit hazardous.  


We're working with acids and bases, 
both of which can be dangerous.  


Getting it on your hands, because we're working with weak solutions, really shouldn't be a problem 


so if you spill you just want to rinse your 
hands off in water as quickly as you can.  


I'm wearing a laboratory apron. Spilling acid 
on my clothes may not look like a problem now 


but tomorrow I'll certainly find holes in my clothes if I'm not protected, so be sure and wear a laboratory apron.  


Most important are your eyes.  



Even though the acids and bases we use are not very strong, if it splashes into your eyes it creates a problem, 



so you'll be given a set of goggles to wear.  They might be goggles like this and these work just fine.  


They're really uncomfortable but 
they provide the best protection.  


Here in the laboratory studio today I'm going to use a different kind.  These kind don't steam up quite so bad.  


Put them on.  If you find that wearing the standard goggles give you trouble and tend to steam up 


then ask for a pair of these goggles.  
They work a little bit better.  


So now with the protection in 
store we're ready to proceed.  


We're going to have five flasks that
serve as our artificial stomachs.  


I'm only going to put two out here today because I don't think you need to see me do the entire experiment.  


But again, these are our stomachs and the first thing we want to do is add acid to the stomachs or to the flasks.  



You've got a bottle which is labeled "stomach acid" and working in the lab you always want to read the labels.  


Read them twice. Don't grab the wrong one.  
This is our stomach acid bottle.  


We want to measure out a hundred milliliters of stomach acid.  For that we use a graduated cylinder.  


So we'll uncap the bottle and very carefully 
pour acid into the graduated cylinder.  


Do this slowly, because you want 
exactly a hundred milliliters.  



We want to be as accurate as possible here so that we have a controlled amount of acid in our artificial stomach.  


I'm getting close so I'm going to bring this up 
to eye level so that I can look straight on.  


I'm looking for that top line there and I want to show you something about measuring in a graduated cylinder.  


You might notice that the liquid forms 
a small cup.  That's called a meniscus.  


When you read the graduated cylinder you don't read it at the edge here.  You read it at the bottom of the meniscus.  


So we want to make sure that we're reading here 
at the center, at the bottom of the meniscus, 


exactly one hundred milliliters.  Now, of course 
if you don't have enough you're going to add more.  


If you have too much you want to pour some out.  Once something comes out of a bottle it's considered contaminated 


so if you need to pour out some 
of the acid do that in the sink.  


Turn on the water and pour a little bit of the acid down the drain.  Please don't pour it back in the bottle.  


Remember, once it comes out it's contaminated.  


Well, I want to set up an assembly line here so I'm going to take the first flask and add the acid to it.  


It's a good idea to tip the flask, pour the 
acid slowly in... and that will be one.  


I want to continue pouring out another 
hundred milliliters of the acid.  


This is hydrochloric acid, HCl, and it turns out that the base that we're using, sodium hydroxide... NaOH, 


neutralizes hydrochloric acid. And the results of 
that neutrallization are water and common table salt.  


So in the end we'll have a solution of salt water.  


That's a hundred milliliters.  
Pour that into our next flask.  


And we'll go on down the line filling five different flasks.  Once we've done that, we'll cap up the acid.  


We're done with that now so we'll set that out of the way and we'll set the graduated cylinder out of the way.  


We won't use them again.  



Now, how do we know when our acid 
and base mixture gets neutrallized?  


That's called a titration process 
and we need an indicator for that.  


The indicator that we use is a material 
which is called Phenolphthalein.  


And you should find a small 
bottle labeled Phenophthalein.  



We're going to add ten drops of the Phenolphthalein indicator solution to each of our stomach acids.  


We'll count out ten drops...  


1


2


3


4


5


6


7


8


9


10


Swirl that up.  You don't see anything 
happening here but that's not unexpected.  


Ten in here...  


1


2


3


4


5


6


7


8


9


10


And give that a swirl.  


And you want to go ahead and 
do that with all five flasks.  



The idea of Phenophthalein is pretty interesting.  


When Phenophthalein is in an acidic 
solution it remains pretty colorless.  


When it's in a basic solution it 
gives a very brilliant violet color.  


So we're going to titrate, that is add sodium hydroxide into the flasks, trying to bring that pH to 7, 


showing the acid is neutrallized.  



And at that point, when we've obtained that, we'll find that that our solution changes color.  



It goes from clear to a very nice violet 
color, and I'll show you that in a minute.  


Now, we're going to test four different antacid tablets.  


We've got five flasks. Our 
first flask is called a control. 


It's going to be used to test how much sodium hydroxide is needed to neutralize all the acid 


without any help from an antacid tablet.  
So you should have your flasks set up.  


The first one being called "Control" and 
then label the other ones A, B, C, and D.  


You're going to need a data sheet to record the results and I think probably I'll show you now 


what a reasonable data sheet should look like.  


Here's a data table.  We want you to make 
a data table which is neat and labeled.  



We've got four columns here.  The first one 
is "Flask," and we represent our five flasks.  


The control which will have no antacid 
tablet... and then A, B, C, and D.  


Under "Name" we're going to list the names 
of the four different antacid tablets.  


As we do the test we're going to look to 
see if adding the tablet causes bubbles.  


Some of these antacid tablets have got an extra material which is designed to create bubbles and, 


theoretically at least, that helps the effectiveness.  
So we'll indicate here yes or no for each of the tablets.  


This is the most important column:  "Base Added" 


This means how much sodium hydroxide do we need to 
add to completely neutralize the acid in the flask.  


Here we're going to record the number of milliliters to the nearest .1 milliliter as we do the tests.  


That's the data table that you need.  Make one of 
your own and include that with your final report.  


At this point in the experiment we'd 
like to add those antacid tablets.  


If you just put a tablet into each of the flasks it will take quite a little while for it to dissolve.  


And more than likely if you're taking an antacid tablet you're going to chew it or suck on it 


to help the process of breaking it down.  
Well, we're going to use a mortar and pestle.  


I'll set the flasks out of the way and show you.  


This device is a mortar and pestle.  The 
bowl is the mortar and this is the pestle.  


We're going to use that to grind up the 
antacid tablets. So we'll take antacid A.  


Take one of these out.  And they will each look a little different.  Don't worry about the differences in appearance.  


So we've got our antacid tablet.  We're going to place that into the mortar and break it up with a pestle.  


This is not a hammer.  We're not going to pound on it. 



What we're going to do is press... and by pressing we crush the antacid tablet.  Now, it's not hard to do this 


but the more we crush, probably the faster the antacid tablet will then dissolve in our artificial stomach.  


And that should be good enough.  


What we want to do now is add this 
crushed up antacid tablet to our flask.  


This was Antacid Tablet A so we're 
going to add that into Flask A.  


We can do that using the little scoop which is provided for you 


and just tip this up and scoop 
the materials into the flask.  


Remember that we're also going to be 
looking for bubbling or effervescence.  


We want to add this carefully. Spilling it of course will reduce the amount that we add in and alter our results 


so we want to get as much as possible into the flask.  


Since we're going to want to do this for each of the four tablets, we don't want to contaminate our results 


so at this point we need to clean off our equipment.  A paper towel will work just fine for that.  


And so we want to carefully clean off the 
scoop. Set that aside. Clean off the pestle.  


Probably don't want to wash these.  If we get them 
wet then the ground up tablet will stick to it.  


And clean up the mortar as well.  When 
you do that your paper gets contaminated.  


You can then throw that directly into the trash.  We'll set this aside, and give this a stir.  



Now it may be that you find that you get 
the materials clumping up as we see here.  


You should also find in your 
equipment tub, a glass rod.  


The glass rod can be used for further crushing if you want to.  You can put it down in and break up the materials.  


Remember we're looking to dissolve the antacid tablet. 


Once you get done with that, again, you'll 
have contaminated your stirring rod.  


This one I think probably we want to wash off.  And when we do the washing we use distilled water.  



Over a sink or an extra flask or beaker just squirt with a little bit of distilled water and rinse the stirring rod.  


And we set that aside.  Now you're going to continue on down your assembly line with each of the flasks.  


Remember the control has got no antacid tablet added to it and flasks A through D have the four different tablets.  


Now, while those are dissolving we want to go 
back to our titration apparatus and prepare it.  


For that we need some sodium hydroxide and so again look for the bottle labeled sodium hydroxide.  


Always read labels twice when you're in the 
chemistry lab.  NaOH... Sodium Hydroxide.  


Now we don't really know what this buret in 
the titration apparatus was used for last 



so we want to run a little bit of sodium 
hydroxide through it to help clean it out.  


We're going to carefully take the top off, and going up to the top of the buret we have a funnel and 


we're going to add a little bit of sodium hydroxide.  


And let me say, this is the place in the experiment where I really worry about your safety.  


The buret is quite a tall, unsteady apparatus.  And I'm a little concerned that it may tip while you're working.  


If it's convenient for you, particularly if you're short, you're going to want to get a stool 


and step up onto the stool as you're filling the buret.  


You can see over here now that we do have 
some sodium hydroxide inside the buret.  


What I'm going to do is open the valve and 
just simply drain that material through.  


And that will help cleanse out the system.  It also helps get rid of air bubbles and things like that.  


So we just let that run through.  And when it 
gets down to the end we'll turn off the valve.  


Pretty exciting stuff isn't it...  watching this drain?  


There we go.  Turn off the valve.  


Notice that we've got a drop of 
sodium hydroxide hanging off the end.  


One technique to get rid of that is just tilt the beaker, touch it to the side and that takes care of it.  


Now at this point we need to fill up 
the buret all the way to the top.  


The top mark on the buret reads 0 and in 
fact this scale increases as we go down.  


As we lower the level inside the buret we'll be 
able to see how much sodium hydroxide we've added.  


We want to start out at exactly the 0 mark.  


So again, carefully taking the top off of the sodium hydroxide, we want to begin filling our buret.  


Do this slowly and carefully.  We don't want 
to over fill and spill any of the base.  



And as we get near the top, slow down... 


and that's good.  


See, what I've done is to go over the top, 
over the 0 mark.  Set this out of the way.  


And what I need to do now is to release some 
of the sodium hydroxide, some of the base, 


and bring that level down exactly to 0.  


First we'll give it a few taps in 
case there's air bubbles inside.  


And then let's carefully look up here at the top.  
You can see that the level is above the 0 mark.  


So I want to just let out a little bit of sodium hydroxide from the bottom and drop that down.  


Again, we're looking at the meniscus, 
the lowest part of the curve there.  


We want to bring that right down on to the 0 line. 


And that's good right there.  


You notice that I've always got 
something underneath the buret, 


some kind of catch thing so that the base 
doesn't fall on our automatic stirrer.  


At this point, we're set up ready to conduct the 
first test. We're going to test first our control.  


That is the flask, or artificial stomach which 
has got no antacid tablet.  It's all pure acid.  


To help us mix up as we go along we're 
going to use a little magnetic stirrer.  


It's just a little slug that looks like this and 
we've got a removal rod which is a magnet inside.  


And we put the magnet on to the stirrer.  


Put that down into the flask and... we should 
be able to just knock this right off.  


If you have a little trouble then go back to your glass stir rod, hold that down, and pull it free.  


These, I want to give a rinse before I go on, because remember they have a little bit of acid on them.  


Then again, set these aside.  Now we're going to place the flask underneath the buret so remove the extra catch.  



And I can see when I put this up here that 
I'm going to have a little bit of trouble 


so that tells me I want to raise up the buret just slightly.  


There's some clamps here on the side, if you 
squeeze these clamps it releases the buret.  


Do that carefully and raise up the buret so that 
you can then easily slip the flask underneath.  


With the flask in place we come to the automatic stirrer.  


Turn that on and when we do we should see that the little stir inside the flask begins to rotate.  


We'll just set this at a low speed so 
that it is mixing things up for us.  


That's good.  We're now ready to begin the titration.  Inside the flask is a hundred milliliters of acid.  


We're going to add enough base to neutralize it.  


We'll know when the neutrallization process is complete because the liquid is going to turn violet color 


due to the Phenolphthalein that we added earlier.  


So we begin.  


This is a slow process.  Some people 
think it's a time consuming process.  


We slowly open the valve and add 
a little bit of Phenolphthalein.  


From my perspective, I can see 
that there is a color change 


at the point where the sodium hydroxide 
is dropping into the flask.  


I'll turn this around a little bit 
so you might have a clearer view.  


We're going to slowly drop in 
the base, the sodium hydroxide.  


Each time a drop falls in, we 
see a slight violet color.  


We're looking for the entire flask to turn violet and for that color to last for more than 30 seconds.  


Now this does take some time to do, but we can't just open the valve and dump a whole bunch of base in.  


If you do that you'll go beyond the end point, beyond neutrallization.  So we have to slowly, slowly add.  


You're probably not seeing the color as well as I am.  And perhaps if we turn off the stirrer for a moment 


and if I add the base, you'll be 
able to see it a little bit better.  


See that purple color or violet 
color which is forming?  


Remember we want the whole solution to 
turn violet, and for that color to last.  


As soon as we give this a swirl the violet goes away which says we're not at the point we want to be yet.  


So I'll just keep adding and adding. 



In the old days you had to add a drop at a time and swirl it.  Add a drop at a time and swirl it.  


And this was time consuming and boring.  


That's why we've got this stirrer for us.  
That takes care of the swirling process.  


So I'll turn this back on.  And continue to add the sodium hydroxide... just a few drops at a time.  


When we get near the end we'll be able to see that quite clearly because the violet color will tend to last for some time.  


Now, I'm really going faster than 
I'd like you to go in the lab 


because I don't want to take your time 
while you're watching this video.  


Certainly if this is your first experience 
with titration you will want to go slowly.  


You're probably getting bored right now aren't you?  


That's okay.  



We notice that each time we add the base we get 
a violet color but it disappears quite quickly.  


You'll know that you're getting near the end point or neutrallization when the color seems to last a little bit longer.  


And here I think you can see that the purple 
color is lasting locally for a second or so.  


And we just continue on... 


If I could sing, I'd sing you 
a little song to entertain you...  


We are getting pretty close here because 
I see that purple color is making it around.  


It's swirling around in the flask.  And making a whole revolution.  And it's getting a little stronger.  


One of these days we'll get there.  


Now the purple color is actually lasting a couple 
of seconds so I know I'm getting near the end.  


And when I get near the end then I need to slow down 


because just one or two drops will make all the different in the world.  


We're pretty close now.  


Here, just adding a single drop gives us a 
violet color that lasts for a couple of seconds.  


And that's the key that you're very nearly there.  


You can see how we get quite a change and 
the change is occurring not at one spot 


but it's tending to be throughout 
the entire volume of the liquid.  


When you're doing this in the lab you're going to find it more interesting than watching me do it I'm sure.  

The purple color is really holding 
on there right in the center.  


Now, we're looking for the entire flask to 
turn violet, not just a locallized point.  


We're almost there.  


Don't you get frustrated and just give it a good blast.  When you get close like this, go slow.  


Almost there now.  We're getting a 
big cloud each time a drop goes in.  


And look at that.  That was a big one.  
That, I think, is one step away.  


Remember that we want the violet color 
to last for 30 seconds or more.  


So putting one more drop we'll see a big change occurring.  


And that color seems to be lasting.  Eventually it does fade.  I'll put in one more just to be certain.  


And that is our end point.  We see 
quite a big change in the color.  


Well, at this point we're ready to take some results.  


We'll go to the buret and we'll see how 
much sodium hydroxide we had to add.  


And I can see that it's right here.  
We want to read that level.  


Remember that the numbers increase as we go down so here we've got 29 and 30 and we're just below the 30 here 


so I'd probably read that as 30.2
Record that in your data sheet 


as the amount of base needed to neutralize the 
stomach acid when no tablet has been added.  


We can turn this off now and remove our first test.  


Remember we always want to put something 
underneath the buret so we'll put that back.  


Now we need to get the stirring stick out 
of the first flask and into the second.  


And again, it's been contaminated 
so it will need to be washed off.  


We'll reach down with a magnetic wand and 
pick that up.  Put it over the beaker.  


Again, using distilled water, rinse that off.  


And then we'll add the stir rod into the flask 
labeled A, which contains our first tablet.  


And again you may need to use the 
glass rod to separate the two.  


Now I've reattached again... silly boy.  


You want to rinse these off once
more and we'll set these aside.  


Now, before we can test this, we 
need to refill our buret again.  


So back to the top with the sodium hydroxide 
bringing it back up to the 0 level.  


Again, doing this carefully, slow down as you get 
near the fill mark.  Go a little bit beyond the 0.  


We'll cap this up and set it aside, 



give a few taps, get out the air bubbles, 
and then we'll drop this back down to the 0 


...and that's good.  


Now, we're going to put Flask A with our first 
tablet underneath.  We'll turn on our stirrer.  


And we begin to titrate with the 
first of our test solutions.  



Now I'm going to do something that I don't want 
you to do.  I'm going to go rather quickly because 


I want you to see that it's a little more difficult 
to find the end point when the solution is cloudy.  


Again, I want you to be just as careful 
and slow as you were with the control.  


But here, because the antacid tablet has already neutrallized some of the acid we find that 


less of the sodium hydroxide is 
needed to reach the end point.  


Again, we get the same violet color 
but it's not quite so clear.  


Almost there now.  


Now this does have a faint hue to 
it so I think we're nearly there.  


Good.  


Well, that should finish up this so we can 
turn off our stirrer, and remove our flask.  


Put our catch beaker in place.  And 
we've done two of the five flasks.  


Your job will be to continue 
on with Flask B, C, and D.  


Once you've done that you have completed the experimental part except for one very important function 


and that's clean-up.  


Remember that results, particularly in 
chemistry, are altered by contamination.  


You're done with your experiment but there are 
other students who are going to follow you 


and you want to leave nice clean glassware for them.  


All the solutions that we have can be dumped 
down the drain as long as the water is running.  


Remember in our neutrallized solutions all we have is salt water left so certainly they can be dumped down the drain.  


Carefully remove the buret from the titration apparatus and pour that remaining solution down the drain as well.  


And then scrub up really well.  We'd like you 
to use the soap solution provided in the lab 


along with brushes to clean all the glassware; 
the beakers, the glass, and the buret.  


Once they're clean you'll rinse them with tap water 


and finally rinse them again, 
this time using distilled water.  


All the glassware is going to be mounted 
upside down so that it can drain and dry 


and that way the next students who comes 
along will have a good set to work with.  


We'll assume that we're done now and I'll remove my glasses and mention a few words about the end of the experiment.  


At this point you should have a pretty clear 
idea of which tablet is the most effective.  


The question then is, How do 
you communicate those results?  


We'd like you to write a written laboratory 
report... not simply fill in the blanks.  


In your laboratory manual you'll find a set of instructions on writing a scientific laboratory report.  


Your report probably should be typed.  
You should have a cover sheet on it.  


And then the actual body of the 
report is broken down into sections.  


We'd like you to do that when you write your report.  Starting with the purpose, state what you're trying to do.  


Then a list of apparatus, tell 
the equipment that you used.  


Then the method section which will have 
a short part describing what you did.  


Remember that in scientific writing we don't use "I" or "we."  In fact we use third person passive voice 


so you want to say things like "the 
buret was filled with sodium hydroxide" 



instead of saying "I filled the
buret with sodium hydroxide."  


Then we come to the result section of the report.  


In the result section you should 
indicate the tablets that you used,  


Whether they effervesced when 
added to the artificial stomachs, 


and how much sodium hydroxide was 
added to neutralize the acid.  


At the very last, you want to write your conclusions.  


There you'll list the tablets in order of effectiveness and indicate which tablet you would buy.  


Now, you may not choose the one that was the best.  


You may have some others factors in mind in making your selection.  You'll want to include your data sheet.  



You'll also want to include a bar chart showing your results.  Please do that on standard graph paper.  


And then you'll also find a little quiz of understanding in your laboratory manual.  


Take that quiz and attach that to your report as well so you'll have several sheets to turn in to your instructor.  


I really hope you enjoyed this experiment.  


It is putting you in the place of a chemist who's testing whether or not advertising claims are valid.  


That's all for today so until we see you next time, bye for now.