TEACHER BACKGROUND INFORMATION - STELLAR

© S & K Associates. May be copied with permission from Karen Ostlund or Sheryl Mercier.

© S & K Associates. May be copied with permission from Karen Ostlund or Sheryl Mercier.

© S & K Associates. May be copied with permission from Karen Ostlund or Sheryl Mercier.

© S & K Associates. May be copied with permission from Karen Ostlund or Sheryl Mercier.

5-Petal Flower Template
© S & K Associates. May be copied with permission from Karen Ostlund or Sheryl Mercier.

© S & K Associates. May be copied with permission from Karen Ostlund or Sheryl Mercier.

© S & K Associates. May be copied with permission from Karen Ostlund or Sheryl Mercier.

© S & K Associates. May be copied with permission from Karen Ostlund or Sheryl Mercier.

© S & K Associates. May be copied with permission from Karen Ostlund or Sheryl Mercier.

© S & K Associates. May be copied with permission from Karen Ostlund or Sheryl Mercier.

Paper is made of cellulose fibers. Cellulose is a polymer. A polymer is a compound
made of repeating units. The repeating units in cellulose are sugar molecules that
are linked together to form a chain. Cellulose is an organic compound because it
contains carbon. The generic chemical formula for cellulose is (C6 H10 0 5 )n.
When you bend the petals of the paper flowers, the cellulose chains in the fibers
move so the paper will bend without breaking. If paper is bent gently, it will go back
to its original position. When a substance can bend elastically, we say it is pliable.
When you put the paper flower in water, the cellulose fibers in
the paper are attracted to the water so the water enters
the chains of cellulose. Water makes the paper flower pliable.
The water absorbed by the cellulose in the paper flower
causes the paper petals to unfold.
Where the petals are bent, the swollen cellulose fibers push
the petals back to their original position.
Heat also makes the cellulose chains in paper more pliable. What do you think
would happen if you used warm water and cold water in your investigation?
How do real flower buds open?
Within each flower bud is a completely developed miniature flower (petals, sepals,
etc). In order to bloom, plants utilize a mechanism similar to how they grow other
cells. The cells in the flower petals swell from turgor pressure exerted by the
uptake of water. This expansion of cells is mediated by plant hormones, such as
the auxins, which affect the elasticity of the cell walls.
© S & K Associates. May be copied with permission from Karen Ostlund or Sheryl Mercier.

TEACHER BACKGROUND INFORMATION
Paper is mainly made of cellulose, a natural polymer
(molecule composed of many units), built by stringing
together thousands of individual sugar molecules into long
chains. The molecules that make up cellulose cling tightly to
one another at room temperature and make it rather stiff
and brittle just like the sugars that make up the molecular
units in cellulose. The chains of cellulose are so entangled
with one another that the cellulose couldn't pull apart even if its molecules didn't
cling so tightly. That is why it's so hard to reshape cellulose and why paper doesn't
melt; instead paper burns or decomposes. In contrast, chicle, the polymer in
chewing gum, can be reshaped easily at room temperature.
Even though melting can’t reshape pure cellulose, it can be softened with water
and heat. Like sugar, cellulose is attracted to water so water molecules easily
enter its chains. This water lubricates the chains so that the cellulose becomes
somewhat pliable (heat increases that pliability). When you iron a damp cotton or
linen shirt, both of which consist of cellulose fibers, you're taking advantage of
that enhanced pliability to reshape the fabric.
But even dry, fibrous materials such as paper have some pliability because thin
fibers of even brittle materials can bend significantly without breaking. If you bend
paper gently, its fibers will bend elastically and when you let the paper relax, it will
return to its original shape. When the cellulose in the paper flower absorbs water,
it causes the cellulose to swell where the petals are bent and the petals begin to
go back to their original position.
However, if you bend the paper and keep it bent for a long time, the cellulose chains
within the fibers will begin to move relative to one another and the fibers
themselves will begin to move relative to other fibers. Although both of these
motions can be affected by moisture and heat, time alone can get the job done at
room temperature. Over months or years, a sheet of paper in a tightly rolled shape
will rearrange its cellulose fibers until it adopts the rolled shape as its own.
However, when you remove the paper from its constraints, it won't spontaneously
flatten out. You have to reshape it again with time, moisture, and/or heat. If you
press it in a heavy book for another long period, the paper will adopt a flat shape
again.
© S & K Associates. May be copied with permission from Karen Ostlund or Sheryl Mercier.