Elmers glue and other comparable school glues are polyvinyl adhesive (PVA). Slime is made by mixing PVA glue with a solution of borax. Slime is a polymer, which is a chemical consisting of large molecules made of a linked series of repeating units called monomers.
The polymer slime produced is not as runny as the PVA glue and borax solution used to made the slime. Actually, scientist prefer to use the term viscous instead of “runny.” So, a more scientific description would be:
The reason for this increase in viscosity is that borax forms links between the PVA molecules. Visualize a ladder with the vertical sides being PVA molecules and the steps of the ladder being borax links.
Slime can be described as being made of cross-linked polymer chains. These cross-linked molecules have less flexibility than do the unlinked PVA molecules or watery borax solution. Thus, without links, the glue molecules are able to flow over and around each other while the linked PVA molecules that make up slime cannot. This is why slime is more viscous–less runny–than PVA glue.
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