Page 1
Joke Juice
Recommended Grade Level(s):
Appropriate for: All grade levels
Time Requirements:
Activity Time: 10 minutes
Teaching Topics & Concepts:
Illustrate the effect of cross-linking on a polymer.
Background:
Polymerization is a critical chemical process that produces many prod-
ucts found in our everyday lives. Polymerization occurs when small
molecules (monomers) join to form long chains containing a repeating
group. Some polymers form naturally, while others are manufactured by
humans. In polymer chemistry, "cross-linking" refers to the use of cross-
links to cause a change in the polymers' physical properties. By selecting the monomer and controlling the amount of cross-link-
ing, chemists can pick and choose the properties of polymers they synthesize and develop exciting new polymers.
Students can complete this activity using a natural polymer, guar gum (a polysaccharide), to make an ooey-gooey mixture that
demonstrates cross-linking principles.
Materials:
• Guar gum
• Borax, sodium tetraborate decahydrate, Na2B4O7 • 10H2O
• Red food coloring
• Glass stirring rod
• Empty glass juice bottle (~300 mL)
• Distilled water
• 100 mL graduated cylinder
• 100 mL beaker
• Electronic balance
+
ward
'
s
science
Safety
• Read the SDS sheets for all chemicals before using them.
• Wear safety glasses and gloves.
• Remove the original label from the juice bottle and clearly label the container to ensure it is
not mistaken as drinkable juice.
!
