11. Sandwich bag dart boards
• Materials
– Pint or quart-size
plastic bags
– Several sharpened
pencils
– Water
– Sink, pan or bucket
12. What is happening?
• Most plastics are made
of very long molecules
called polymers.
• Sandwich bags are
made of polyethylene
which consists of many
polymers forming a
web of molecules.
• The molecular web,
with all its connections,
resists being torn.
14. Salt engineering
• Materials
– Ruler
– Cardboard tube
– Tissue paper or
wax paper
– Rubber bands or
masking tape
– Table salt
– Broomstick
15. What is happening?
• The tiny salt crystals
transfer most of the force
we apply toward the walls
of the cardboard cylinder
instead of straight down.
• Trusses and beams
made for bridges and tall
building use similar
designs to spread or
change the direction of
forces and loads.
17. Take a stab at it!
• Materials
– Potato
– Straw
18. What is happening?
• The air trapped inside the
straw gives the straw
enough strength to
penetrate the skin of the
potato.
• As the straw enters the
potato, the potato plug
compresses the air inside
the straw, increasing the
air pressure, and
strengthening the straw.
20. Alka Seltzer Rockets
• Materials
– Film canister with a
snap-on lid
– Water
– Alka-Seltzer tablet
21. What is happening?
• A chemical reaction
occurs between the
water and the Alka-
Seltzer tablet creating
carbon dioxide
bubbles.
• The CO2 gas builds up
pressure inside the
film canister until the
force is so great that it
has to escape.
