PVA to Gak
A study of hydrogen bonding.
can use the long polymers in PVA glue to make Gak. Gak is viscoelastic
material that can be squeezed and stretched.
|Place 15 ml of PVA glue into a beaker.
|Add 25 ml of water.
|Now add 5 ml of talcum powder and stir thoroughly. The more talcum powder that is used the less the putty will flow and be stretched.
|Add one drop of food dye.
|Add 5 ml of borax solution. The mixture should immediately thicken and adhere to the spoon. Stir the mixture and remove the putty from the spoon
|Work the putty in your hands until it is dry and smooth.
of senior chemistry to explain the formation of Gaki stuff.
As soon as the borax is placed into the PVA the mixture thickens. Something is holding the long PVA polymers together. But at the same time they are not permanently held in place as the putty is allowed to run and form new shapes. The chemistry behind this is very simple. Below is a diagram of how this occurs. The borate ion form temporary bonds with the polymers. These bonds are formed by hydrogen bonding and can be easily broken and reformed. These allows the polymers to slide past each other while still being kept together.
|On the right is an animation of how hydrogen bonding breaks and reforms as the polymers slide past the borate ions. Click to see a larger image of the animation.
Consider the animation above.
Between what two atoms does
hydrogen bonding occur?
|When hydrogen and oxygen bond together small charges appear on the oxygen and hydrogen atoms. A small positive charge appears on the hydrogen and a small negative charge appears on the oxygen. These charges attract each other as shown on the right. The attraction is known as hydrogen bonding.
Click to see an explanation of how hydrogen bonding comes about and answer the following questions.
The atom that attracts the
electrons the strongest has