SM07 Actua Project Sharing
Project Write-up
Name of project: Mood bracelets
Submitted By: Andréanne Baribeau
Overview
Participants will learn about liquid crystals and how these materials are part of a special class of
matter: not quite solid and not quite liquid. Liquid crystals can be introduced by talking about their
implications in life, such as in electronic displays for computers, cell phones, digital cameras etc.
Participants will learn the difference between smectic, nematic and cholesteric liquid crystals and
how these last ones react very well to temperature changes (by changing colors), making them
ideal for building mood rings or mood bracelets. They will then build a mood bracelet which they
can bring home!
Topic Area(s)
Grade Level
Cost
Time
Learning Outcomes
Chemistry (liquid crystals)
Grade 5-7
2 hours
 Hands on chemistry experiment: Everyone gets to make their own
mood bracelet and bring it home with them
 Understand the classification of matter: solids, liquids, gases
 Understand that liquid crystals are part of a special matter class:
between solids and liquids. They exhibit the same behaviors as
crystals but appear to be in a liquid form.
 Learn where we use liquid crystals
 Understand the difference between smectic, nematic and cholesteric
liquid crystals.
 Understand that cholesteric liquid crystals will reflect different
wavelengths, depending on its temperature. This is why the mood
ring changes colors.
Hook
Have you ever wondered how LCD’s (liquid crystal displays) work? Or why a mood ring changes
colors? During this chemistry activity, you will learn about liquid crystals that are used in screens of
computers, digital cameras and even cell phones, as well as the ones used in mood rings. You
even get to build your own mood bracelet!
Background Information
We learned that matter is classified between solids, liquids and gases. This classification system is
not absolute; there are certain compounds that have intermediate properties. Liquid crystals are
organic compounds composed of oxygen, hydrogen, carbon or nitrogen (and a few other elements)
that are in a state between solid and liquid. They exhibit the behaviours of crystals (such as optical
properties like reflecting and scattering incoming light) and the molecules are arranged in a crystallike way, but the compounds can flow like a liquid. The compounds can have the appearance of
powder at room temperature, but heating is up causes it to go into a liquid crystal phase.
There are three types of liquid crystals: (the molecule can be pictured as a long a narrow unit)
-smectic: Molecules arranged in horizontal layers. They stand vertically or can be on a tilt.
-nematic: Molecules arranged so that their long axis are parallel. They can only rotate along that
axis.
-these liquid crystals are used for LCD’s. Electric fields are used to line up the molecules. In
a screen, a small voltage can be applied to switch the liquid crystal between its transparency and
opaque form. These LC have low viscosity at room temperature and can stay in this liquid crystal
phase between -5 oF and 200 oF.
-cholesteric: Molecules are grouped into layers. On each layer the molecules are all parallel, but their
orientation can shift from one layer to another.
-these LC are used in mood rings since they vary in colour depending on their temperature.
They are also used as temperature indicator for the body or on machinery to show overheating.
Materials
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Cholesteryl oleyl carbonate
Cholesteryl pelargonate
Hot plate
Ice bath
Spatula
Watch glass
Weighing scale
Transparencies
Photo slides (only the metal frames)
Black cardboard
Safety Considerations (if necessary)
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Wear gloves, lab coat and lab goggles
Keep the hot plate on low.
Procedure
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Cut 3 equal square pieces of transparency, a little smaller then the slide frames
o Set aside
Cut a square piece of black cardboard the same size as the transparency pieces.
o Set aside
Weigh equal parts of cholesteryl oleyl carbonate and cholesteryl pelargonate. Each person
only needs a small amount of both chemicals: about 0.05g of each (perhaps even less… the
supervisor should test this before hands, to find the smallest quantity needed).
Put both chemicals onto the watch glass and put the watch glass on the hot plate.
Gently warm and mix the two chemicals until the mixture has the appearance of water. DO
NOT OVERHEAT NOR ALLOW THE MIXTURE TO PRODUCE SMOKE.
With the spatula, spread a THIN layer of the mixture onto one of the transparency piece.
Place this piece on top of the black cardboard. You should have 2 remaining transparency
pieces. Put one on top of the mixture, making sure there are no trapped bubbles. Put the
last piece underneath the cardboard. On each side, put a metal slide frame and try to clip
everything in place. Use tape on all four sides to seal everything. You have now a liquid
crystal frame.
Place the liquid crystal frame on ice, than slowly warm the frame with your fingers by
pressing gently. It should change colors: blue (warm), green, yellow, red (cold).
You can tape the liquid crystal frame around the participant’s forearm like a bracelet.
Wrap-Up/Debrief
Ask the participants:
 What was the best thing about this workshop?
 What was the hardest part of this activity?
 What do we use liquid crystals for?
 Do you think a mood ring can really tell you what mood you’re in?
The participants can also test the temperature on different parts of their bodies, such as fingers,
forearms, armpits, under the knee etc. to see which spots are colder/warmer.
The instructor could then show the temperature image of a human body (if available).
Further Resources (optional)
A lot of information as well as the procedure were found in the chemistry Mini-enrichment course
text book of the University of Ottawa: ‘What in the world isn’t chemistry?’ Look for experiment ‘This
is not as crystal clear as it seems to be’.
Also, http://www.opticsexcellence.org/SJ_TeamSite/pdfs/lcmoodpatch_lesplan_v3.pdf has a lot of
information on liquid crystals.