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Chemistry of Slime
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Chemistry Connections
The Chemistry of Slime
Episode #_1_
Welcome to Chemistry Connections, my name is Agathe and my name is Beck. We are your hosts for episode #1 called The Chemistry of Slime. Today we will be deep-diving into the chemistry of slime. We will discuss not only what slime is but also how it is made.
Segment 1: Introduction to Slime
Slime—something we all know and love. Typically, you see it on TikTok or Instagram, where someone mixes glue and an unknown clear substance in a bowl, ultimately creating a fun, rubbery material. It is enjoyable to play with, poke, stretch, and make large bubbles with, but what makes slime the way it is, and what allows it to behave like that?
Slime is made by mixing glue with an activator containing boric acid. Typically, people use borax, a common clothing cleaner, mixed with water and then add it to the glue.
But Beck, what if I don't have Borax, or what if my parents dont let me use such a strong cleaner, especially when I am making slime with my little sister
Others like myself, who prefer to avoid strong chemicals, tend to use baking soda and contact solution. Which works just as well and is much more accessible and safe. The resulting substance is rubbery and molten, yet not sticky, allowing it to be played with for hours. But the interesting question is why is slime the way it is, why is it moldable but not sticky.
Put a pin in that Beck we will talk about that later. Another fun aspect of slime is that it can be tailored to anyone's preferences, with its color, texture, and size changing depending on the added ingredients. This versatility makes slime a popular and customizable activity for many.
Segment 2: The Chemistry Behind Slime
Going back to your question from earlier beck Topic one: The formation of PVA/borate cross-linked polymer (How is Slime Made?)
glue is made up of PVA chains, which are basically long chains of CH2, Oxygen, carbon, and hydrogen. Then we have, borate ions which are found in the activator, which are made up of boron bonded to hydrogen and oxygen. When mixed together, the borate ions bond the PVA chains of the glue together, creating a fishnet structure which is called cross-linking. So beck, What type of bonds connect the Borate to PVA?
Well it is actually hydrogen bonds, which are a type of intermolecular dipole dipole force that is very strong. They are formed when hydrogen is bonded to a very electronegative element, either Nitrogen, oxygen, or fluorine. The resulting bond is very strong and allows slime to be formed. But one thing you will notice is that when making slime it actually get colder, why is that Agathe
Interestingly, the reaction is endothermic, meaning it absorbs energy in the form of heat from its surroundings to form new bonds, causing the slime to feel cold. The endothermic nature of the reaction is due to the formation of these hydrogen bonds, which requires a lot of energy to be created.
Wow! That is so interesting Agathe! Now I know how slime is made. You know, once I made slime and I stretched it so much that it created a big bubble, when it popped it got into my sister's hair.
That is insane! But how does slime get that stretchy? I thought hydrogen bonds were super strong
Topic 2: Why is slime stretchy?
Good question Agathe leading us to topic 2! Slimes' flexible nature is actually due the hydrogen bonds between the borate and PVC molecules.
No way! That seems so counterintuitive.
The hydrogen bonds within slime are strong enough to keep the slime intact when stretched but also flexible enough to allow movement within the polymer network.
Ahhh i see. Wait but last time I made slime with mr johnson he told me to add in lotion he said it would make it stretchier. I told him that didn't sound right to me. Who was right?
Mr Johnson actually is! Adding lotion to the slime introduces glycerin, which interacts with the hydrogen bonds.
Ugh whatever, what even is glycerin
It is an odorless carbohydrate liquid that has a sweet taste and a syrupy consistency. While glycerin occurs naturally in plants through the fermentation of sugars, most of the glycerin nowadays is produced from factories. They are able to form hydrogen bonds with the PVA.
Oh I see so the glycerin replaces some of the existing hydrogen bonds, instead hydrogen bonding to the PVA, making the whole substance weaker and more flexible. But not too much so that it becomes a liquid.
Yes, This results in the slime becoming even stretchier, as the weaker bonds can extend further while still maintaining the overall structure of the slime. Thus, the stretchiness is a balance between the strong, flexible bonds and the weakened bonds introduced by the lotion, providing both resilience and extensibility.
That's so cool. I love that!
Why are we here today
Segment 3: Personal Connections
Well Beck, we both loved the idea of the chemistry behind slime because it is such a simple thing to make that many kids love; however, we never thought of how these liquids turn into solids without heat or outside forces. Many times students don’t remember what is taught in school, however, I believe that when we focus on subjects we enjoy, this is what we will remember for the rest of our lives.
Thank you for listening to this episode of Chemistry Connections. For more student-run podcasts and digital content, make sure that you visit www.hvspn.com.
Sources:
https://stemium.com/slime-science-project/
https://www.ccmr.cornell.edu/wp-content/uploads/sites/2/2015/11/ScienceofSlime_student.pdf
Music Credits
Warm Nights by @LakeyInspired
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