Fun Explanation of Polymers and Chemical Reactions

Kristen Byrnes
8th Kingston Guides
Kingston, ON

Polymer explanation - Polymers are long-chained molecules with repeating units. They are be formed by reacting monomers (the repeating part of the chain) in a process known as polymerization. These reactions fall into 2 main groups - addition polmerization and condensation polymerization. Addition polymerization is adding monomers together to form the chain. In condensation polymerization, a small molecule, often water, is removed as part of the process. Examples of polymers include: polyethylene (plastic shopping bags, toys), polycarbonate (CD's), polystyrene (clear stiff plastic cups), polypropylene (film, rope), Teflon (non-stick coatings), polyester (clothing), nylon (clothing, rope, rugs), spandex (swim suits, biking shorts), kevlar (canoes)

An easy way to explain polymers is the "Mingle Game" - one of my sister's friends came up with it - its funny and a great way to explain molecules and polymers. Some of the kids will likely know about molecules from science tv shows. You can ask the girls questions to get them thinking in the right direction. I've never worked with Brownies but questions we use with Guides which can be adapted include: Holding up a piece of wood or whatever (nothing polymeric - that could come later - I usually start from small to large) - you ask what is the item made of? They'll likely state the obvious (cloth, wood, etc.). Right! But what is wood made of? (the answer is atoms but if they guess molecules then say Right and go smaller) If no one knows, then give them clues - say its soooo small you can't see it..... (any guesses?) Then say there is 3 main parts - the moving part is electrons (any guesses?) the middle part is made up of neutrons and protons (any guesses?)

If you didn't want to ask them questions - I've only worked with Brownies a few times..... You could explain that everything in the whole universe is made up of atoms. Atoms are always moving. And then follow the game/demo.

Basically all the girls are atoms - we explain when atoms are cold they move really slowly [ice is a great example of this] - they all move in slow motion - and then we explain when the get warm the atoms move around more - they bounce up and down in their spot - then we explain when atoms become hot they become excited and can bump into each other - they gently bump into each other [boiling water is a great example of this]- So the different types of atoms are mingling together and they find another atom who want to share some of their electrons. - tell the girls to get into pairs - the pair of atoms is a small molecule (a molecule being more then one atom) - they continue joining other molecules (we usually say that they want to be in groups of 4 or 6 or whatever next - an additive reaction (although there are different ways to make a polymer besides this one)) until they become one long chain of molecules - or a polymer. So then you explain that a polymer is basically molecules joined together to form a long chain. [if you wanted you could explain that most atoms wanted to share electrons with another atom to form a molecule but they had to share the right number so they had the same amount of electrons as protons - you could then have the girls form pairs with girls depending on hair or eye colour as an example)]

[The reason it was called a mingle game is the girls say mingle mingle mingle while joining with other atoms or small molecules. It is also a great way to meet others in your group (we have done different exercises like interviewing or making statues or monsters etc. with different group sizes).]

Chemical reaction explaination- A basic definition is: Reactants (or thing(s) to be reacted) are mixed under certain conditions to cause the atoms to rearrange and form another compound.

You could have a group of molecules (from the above game) and ask them to form one shape - tell them they are being heated by the hot sun (or whatever) and the atoms want to move as they get excited - they break their current bonds and make new ones - have them rearrange themselves in a different shape.

Demos help a lot - a simple reaction to show is viniger and baking soda -they react to form Carbon dioxide. This is an acid-base reaction. I like this demo as there are 3 phases (solid, liquid, gas). You can explain that the liquid viniger and the solid baking soda combine to form carbon dioxide gas, sodium acetate and water.

It would be fairly simple to have the girls act this out chemically too. You could tape the parts of the reaction onto their uniform.
The full reaction is:

2CH3COOH (viniger) + NaHCO3 (baking soda) ----> CO2 (carbon dioxide) + H2O (water)+ 2NaCH3COO (sodium acetate - disolved)

Since there is quite a few atoms - it would be best to put on sections. From the viniger two girls could have CH3COO (acetate) taped to them and 2 girls could have an H (hydrogen) on them. For the Baking Soda one girl (or depending you could have 2 girls each with a Na) could have 2 Na (sodium), one girl would have C (carbon), and three girls (or two girls - one would have 2O and the other would be 1 O) would have an O (oxygen) each. Put the two groups together and they rearrange themselves to make carbon dioxide, water and sodium acetate (which is disolved in the water). The equation should be posted on the wall or the floor so the girls know how it should look when finished.

You could also mention or have them give examples of a fast reaction (like an explosion or your demo is relatively fast) and a slow reaction (like rusting of metal).

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