DAY 9
CHEMISTRY SUMMER SCIENCE INSTITUTE
CONSUMER CHEMISTRY
Most of our students will not end up being chemists but they need to understand the chemistry
principles that affect their everyday living and their health. They also need to know that
“chemicals” are not bad guys but are part of all matter. What follows are some activities that use
household products and employ science concepts and science process skills.
Here is a cute Environmental Protection Agency web site that
takes kids on a tour of the chemicals in their homes with emphasis
on those that are toxic.
www.epa.gov/kidshometour
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CHEMISTRY SUMMER SCIENCE INSTITUTE
DETERGENT ADDITIVES – BRIGHTER THAN WHITE
Certain detergents and fabric softeners claim to make your clothes brighter and cleaner looking.
Some of these products contain chemicals that are called “brighteners.” These chemical absorb
invisible ultra-violet light and re-emit this light in a form that we can see, that is, as visible light.
Some products also contain molecules that absorb yellow light so things look “whiter”. These
materials are blue in color.
1. At this station, there are five samples of various detergents and fabric softeners that have
been poured into flat plastic bottles. There is also a lamp which emits invisible ultra-violet
light.
Examine each liquid and describe it in the data table below. Then, place each bottle under
the UV lamp and describe what you see. Decide if the liquid contains optical brighteners.
NOTE: Try this with various kinds of white paper.
Name of Product
Appearance in Room
Light
Appearance in UV
Light
Which products contain whiteners? Explain your choices.
____________________________________________________________________
____________________________________________________________________
Which products contain brighteners? Explain your choices.
____________________________________________________________________
____________________________________________________________________
Are there any questions you would like to ask?
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CHEMISTRY SUMMER SCIENCE INSTITUTE
STOMACH ACID - WHICH RELIEF IS BEST?
Now that you have studied acid and bases we can put that knowledge to good use. You know
that stomach acid is HCl, hydrochloric acid. But, did you know that it has a concentration that
can dissolve nails or tooth enamel? Luckily our stomachs have a mucus membrane lining that
protects it. “Heartburn” occurs when acid backs up into the unprotected esophagus.
Antacids are alkaline compounds that neutralize stomach acid. They
are not so harsh that they affect the throat or stomach themselves.
How can we determine the effectiveness of different antacids?
We can determine their relative effectiveness by finding out how
much synthetic stomach acid is consumed by a tablet of each brand.
Since we are comparing single tablets (typical dosage) we don’t need
to mass the tablet but it is better to analyze if crushed. What do you
need to be careful of when getting the sample ready?
Some antacid brands produce carbon dioxide gas when reacting with acid. This carbon dioxide
will dissolve in water to form more acid so to ensure accurate results we use a technique called a
back titration. We add more acid than the tablet can handle, heat the sample to get rid of any
carbon dioxide and then determine how much acid is left over by adding another base until
everything is neutral.
antacid
+
left-over HCl
excess HCl 
salt
+ NaOH  salt
+ left-over HCl
+ water
1. Select an antacid brand that your group will use and take three tablets. Using
a mortar and pestle, crush one and completely the transfer the powder to a
250 mL Erlenmeyer flask. Repeat for the other two tablets. Put two of the
flasks aside for now.
2. Using a beaker, fill a buret with a little bit of 0.1 M HCl and rinse it
around the barrel and through the tip. Close the stopcock and fill the buret
with HCl above the zero mark and let it run through the tip until the level
sits on the zero line. Dispense the HCl into the first flask to the 50 mL
mark near the bottom. (Don’t go beyond the 50 mL mark since it is
uncalibrated below this point.)
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CHEMISTRY SUMMER SCIENCE INSTITUTE
3. Put the flask on the hot plate and bring it to a boil. When it boils, continue heating for two
minutes. Carefully remove the flask with “hot hands” and let it cool. While it is cooling
prepare the other two flasks in the same way.
4. Add 4-8 drops of bromothymol blue indicator to the flask. If the solution is blue, pipet an
additional 10.0 mL of 0.1 M HCl into the solution and boil again.
5. Clean and fill a second buret with 0.1 M NaOH. While swirling, slowly add NaOH to the
cooled flask until the color just changes from yellow to blue. Record the amount of NaOH in
the data table and results.
6. Repeat the titration with the other two flasks.
7. Since the concentrations of the acid and base are the same we can determine how much acid
was used by the tablet by subtracting the amount of NaOH used from the amount of HCl
added to the tablet.
Amount of HCl used by tablet = amount of HCl added to the tablet – amount of NaOH used
8. Compare your results with other groups to determine the best antacid
Brand
Tablet
Amount of HCl
(mL)
Amount of NaOH
(mL)
1
2
3
Average
4
Amount of HCl to neutralize
tablet (mL)
DAY 9
CHEMISTRY SUMMER SCIENCE INSTITUTE
TO A WHITER SMILE: AN ANALYSIS OF TOOTHPASTE AND POLISH
Toothpastes and polishes generally contain two major components. One component is a
detergent that washes away materials that are water soluble or can be attracted to a detergent
molecule. The second primary ingredient is an abrasive that scours away materials that adhere to
teeth and cannot be removed by the detergent. Of course, most toothpastes also contain
flavorings to make the mixture enticing and may have whiteners and brighteners.
The following activity explores the relative amounts of these two ingredients in some
commercial tooth cleaning products.
Foam (Studs) Test
1. Put a dab (pea-size) of toothpaste on the edge of a straw. Carefully slide the straw down
the side of a test tube so that no toothpaste touches the wall of the tube. At the bottom of
the tube, turn the straw around so the toothpaste adheres to the wall.
2. Fill the test tube 1/3 of the volume with distilled water.
3. Cork the tube and shake 15 times. Immediately measure and record the height of the
foam column in cm in the data table on the next page.
4. Repeat with 3-4 more samples being careful to shake with the same force each time.
Why is it important to shake the same numbers of times with the same force?
Stain Removal Test
1. With a grease pencil make lines 1 cm by 0.5 cm on the bottom or top of a plastic petri
dish. Make as many marks as samples you are testing all on one top or bottom.
2. Place a dab of one of the pastes on a mark. With a gentle
circular motion try to remove the stain. Rate the ease of
removal based on time or number of circuits needed to lift the
stain from the dish. Record your observation in the data
table.
3. Repeat with 3-4 more samples applying the same pressure
each time.
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CHEMISTRY SUMMER SCIENCE INSTITUTE
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CHEMISTRY SUMMER SCIENCE INSTITUTE
Abrasive Test
1. Place pea size dab of each of your samples on the same bottom or top of a plastic petri
dish. Be careful to make the samples as close to the same size as possible.
2. With your index finger, rub each dab in a circular motion noting any grittiness as you do
it.
3. Record the relative degree of grittiness in the data table. High grittiness means high
abrasive power. You may have to do several different toothpaste samples before you can
come up with an accurate “grittiness scale”.
DATA TABLE
Toothpaste Brand
Foam Test (cm)
Stain Removal
Test (number of
circles)
Abrasive Test
(relative grittiness)
Questions
1. Which product(s) has the most detergent (studs)?
_____________________________________________________________________
2. Which is the most abrasive?
_____________________________________________________________________
3. Which is the best stain remover?
_____________________________________________________________________
4. Which would you use? Why?
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CHEMISTRY SUMMER SCIENCE INSTITUTE
_____________________________________________________________________
SUNSCREENS: HOW WELL DO THEY WORK?
With the growing concern over skin exposure to ultraviolet (UV) radiation, manufacturers have
been formulating suntan products, face creams, and lip balms which contain a “sunscreen.” The
sunscreen is a compound which absorbs UV radiation before it can be absorbed by your skin.
A product that has a sun protection factor (SPF) value of 4 means that only 1/4th of the UV
radiation striking your skin is absorbed by your skin. SPF #15 reduces UV exposure to 1/15th
normal. Manufacturers will often explain SPF #15 (or 4) by saying that it means you can stay
out in the sun 15 (or 4) times longer than without protection.
The experiment that follows investigates the screening effect of various products by seeing how
well they block light falling on UV light sensitive paper (like SunprintR or Solar GraphicR).
PROCEDURE
1. Select 4-5 labeled suntan products of various SPF values. Make sure that baby oil is one
of your choices. Obtain a microscope slide and wooden splint for each product.
2. Prepare each slide by putting 1 drop of product on the slide and spreading it EVENLY
over the slide. Try to keep the amount of product the same on each slide.
3. Place the slides on a tray with the sunscreen side UP in order from lowest to highest SPF
value. Take the tray with a sheet of protected sun sensitive paper (keep in the envelope)
outside to a shady spot that is close to a sunny area.
4. Working QUICKLY in the shade, remove the sun sensitive paper and place it blue side
up on the tray. Line the slides, sunscreen side UP, in SPF # order on the paper.
5. Carry the tray to sunny location and allow the paper to react. The blue will fade to white
or very light blue within 2-5 minutes on exposed surfaces. Remove and place the paper
under the tray as soon as the reaction is complete.
6. When you get back in the lab, quickly remove the paper and soak it in water for at least
one minute.
7. Place the sheet on paper towels to dry. Immediately Label each whitish strip with the
SPF number of the sunscreen and analyze the amount of protection the sunscreens
provided. The bluer the paper, the more sunlight was able to strike the paper
Note: The paper will continue to develop slowly in any diffuse sunlight and faster in fluorescent
light so analyze it immediately. Keep it covered to preserve your results longer.
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CHEMISTRY SUMMER SCIENCE INSTITUTE
7. Which product protects best? Explain your selection.
________________________________________________________________________
Which product(s) protects least? Justify your choice
______________________________
What variables might lead to problems in getting accurate results with these samples?
____________________________________________________________________
____________________________________________________________________
____________________________________________________________________
Options
You can try this with sunglass lenses from broken pairs of glasses.
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