Hobbies And Interests
Making Borax Goop
Making goop is easy. Pour 1 1/2 cups of warm water into a container and then add in 2 cups of white glue. In another container, mix 1 1/3 cups warm water and 3 tsp. of borax. Mix both containers well. Then empty the second container into the first and mix again. You can put in a few drops of food coloring at this point if you like. Stir or knead the mixture by hand until all the liquid has been soaked up and the material looks thick. Some people find that borax irritates their skin, so you should wash your hands after working with it and, of course, never eat it.
Chemistry
White glue has a chemical ingredient called polyvinyl acetate (PVA). PVA is a polymer, meaning its molecules are very long and tangled together; which is why glue is so viscous. Borax combines with the PVA molecules and forms bonds between them known as cross-links. This makes the mix thicker than it was and also gives it some odd properties. The reason for these odd properties is that the crosslinked PVA molecules are now more tightly bound to one another than they were in the glue and so they will not flow past each other very readily.
A Non-Newtonian Fluid
Liquids that people commonly see, such as water, flow steadily no matter how quickly they are flowing. These are known as Newtonian fluids, in honor of the scientist Isaac Newton. Other fluids, however, demonstrate an increase in viscosity and become harder to move as more pressure is applied. These are known as non-Newtonian fluids and borax goop is one of these. The most amazing effect of this property in goop can be seen by picking up a handful and letting the goo slowly slip through your fingers like honey. If you then take another handful and quickly pull it apart, it will snap in two, like a broken rubber band.
An Experiment
A block of goop flows with a slow, steady pace down an incline and you can use this to show how glaciers would "flow" during past ice ages. Start with a block of goop about 2 by 6 inches and use a marker to make a line halfway down the top face of the block, from side to side. Sit the block of goop on an inclined plank and leave it for an hour or two. When you return, you will see the goop has slowly moved down the board. The mark on the block will also be distorted, showing that the middle of the goop moves more quickly than the sides. You can use this as an illustration of how a solid, such as a glacier, can move over time.