Water to Wine to Water to Milk
MATERIALS
4 Glasses (beakers)
20 mL of 0.1 M NaOH solution
20 mL of water and Phenolphtalein Indicator
25 mL of 0.1 M HCl solution
20 mL of Pb(NO3)2 solution (with water)
Optional:
Bromethymol blue
Methyl orange
Universal indicator
Mythol Alcohol
CURRICULUM
This activity can be found in many parts of the senior years curriculum.
S1-2-13: Experiment to determine indicators of chemical change.
S2-2-08: Experiment to classify acids and bases using their characteristic
properties.
S2-2-09: Discuss the occurrence of acids and bases in biological systems,
industrial processes, and domestic applications.
S2-2-10: Explain how acids and bases interact to form a salt and water in
the process of neutralization.
PROCEDURE
Of course, our fellow colleagues will know what is going on in the experiment We would
first acknowledge the fact that the 4 liquids are perfectly clear and that they is no powder in
them (initially there was powder to first make the solution, but we don’t tell the students
this). We can either just pour the chemicals together, but that would be a little boring and
straight to the point, leaving little time for observing and evaluating. What we can do is make
a skit out of it.
Teacher: “Now, let’s say that you are at a fancy restaurant. OK? Would you
like some water sir/mame?”
Student: “Yes please!”
Give the student that first solution
Teacher: “Shall I get you anything else to drink?”
Student: “I would like a glass of red wine.”
John Mantolino
Jan Slavicek
Pour the second solution into the first solution
Teacher: “Wait, before you can drink, let’s first see some ID”
Student: “I don’t have any ID.”
Teacher: “Well, then I’m sorry I can only give you water for now”
Pour the third solution into the two
Student: ‘Fine. Can I get a glass of milk?”
Teacher: “Certainly!”
Pour the last solution in the three.
This is probably a good way to present this kind of experiment to younger students, because
they can relate the skit to other experiences in a restaurant, and surely they never went to a
restaurant where you can have any type of drink that can be made by different clear liquids.
So this, you can either explain to the students what is happening, or you can leave it for the
students to figure out what is happening. This type of experiment will leave the students in
awe.
SCIENTIFIC KNOWLEDGE
We are dealing with common acids and bases experiment. The chemical that gives us the
color is the phenolphthalein. When the phenolphthalein is in a solution that is neutral or
acidic, the solution will remain clear, but if the solution is basic, the solution will turn red.
Since we started off with the phenolphthalein in the water, it will indicate that it is neutral.
Now, we add the sodium hydroxide, and suddenly the solution turns basic, and now the
solution is red. So, how do we change it back. We need to neutralize the base. We start
pouring the hydrochloric acid. Even though there is now acid in the solution, the acid will
mix with the base, and so each will neutralize, but there is a lot of basic solution. We need to
keep pouring acid. Once all the base has been neutralized, the solution will go from basic, to
neutral, so the solution will be clear again, and if we still add some acid, the solution will be
acidic and the solution will remain clear. So now, we have an abundance of acid, we then
add that mixture to the lead nitrate solution. The two chemicals will then combine and form
a white precipitate in the final beaker.
AS A DISCREPANT EVENT
The idea of a discrepant event is to figure out why strange results occur. In this case, the
strange event occurs when 2 clear liquids combine and produce a red transparent liquid, as
well as later on, 2 clears liquids combine to form a white precipitate. This is very puzzling.
Normally, when we look at liquids, we judge their transparency and color. If we were to mix
cranberry juice (a red transparent liquid) with milk (a white opaque liquid), it will then mix
itself into a red-pinkish semi-opaque liquid. Usually when we mix the 2 liquids, we can
predict the color of the liquid. In this case, it is completely different. If we were to add
water to water, we would still get the same clear liquid, but usually when we see a clear
liquid, we think of it as being water. Now 2 clear transparent liquids form together to create
a red liquid or a white precipitate. It just appears like magic. What we have to realize is that
John Mantolino
Jan Slavicek
when we mix liquids like cranberry juice with apple juice, no chemical reaction is taking
place; we could say we have a mixture of cranberry-apple juice, while in the experiment the
“juices” completely changed. If we are to treat our chemicals from the experiment like
juices, we would say that they aren’t juices anymore.
EXTENSION
Along with this experiment, we can change it around a bit. For the original experiment,
we use the Phenolphthalein Indicator. What would happen if we used a different indicator.
We would still have the same experiment, but we would have different colors.
What would happen if we used methyl orange as an indicator? If we followed the same
procedure, the combination would be first orange, then reddish color, then orange-red, and
then a white precipitate.
What would happen if we used bromethymol blue as an indicator? We would first start
off with green, then we would get blue, then a yellow, white wine color, and then white
precipitate.
Lastly, we could use what is called the universal indicator. This is a combination of all 3
indicators: methyl orange, bromethymol blue, and phenolphthalein. With the combination
of the 3, we will get an arrange of colors. Starting from the water with blue, then purple,
then yellow, and lastly a white precipitate. With each different indicator, you can change the
skit around (purple can be grape juice, or yellow can be white wine, and then red could be
red wine).
One should also notice that when doing this extension, you should have some sort of
alcohol on hand, because the indicators, if they are in their powdered form, won’t dissolve in
water. Only alcohol can dissolve the indicators.
EQUIPMENT AND SAFETY PRECAUTIONS
We are working with some very strong acids and bases. Before the actual presentation,
you must first prepare the chemicals, and that is probably the most dangerous. First of all, a
lot of these chemicals have to be diluted. Sodium hydroxide is in a solid salt-like form that
must be dissolved in water. Lead nitrate is also in a powder form that also must be dissolved
in water. Hydrochloric acid is a strong acid, and must be poured into a beaker of water; not
water poured into a beaker full of acid. The mixture between the acid and water will
probably be the most violent reaction; a lot of heat is generated from the beaker when the
water mixes with the acid.
During the presentation, you should still watch out, because the mixture of chemicals do
still generate a little bit of heat. Of course, the necessary safety precautions must be
established: wearing rubber gloves in case of a splash, goggles to protect the eyes, and if
need a fume hood, but if the chemicals were diluted properly, a fume hood wouldn’t have to
be necessary.
To dispose the chemical, just simply pour them down the drain in the chemistry lab. The
strength of these chemicals will have weakened during the experiment, and therefore are not
considered a huge threat.
John Mantolino
Jan Slavicek
REFERENCES
www.nipissingu.ca/department/education/geraldl/sciencegeneral/discrepant_events.htm
John Mantolino
Jan Slavicek