Chemistry is fun but the word chemistry is very scary to most people. In order to get people involved I find the following three experiments to peak the interest of most adults and children. Of course, blowing things up is always another eye catcher. These are all safe and easy to do experiments with a tangible reward in the end. The three experiments are the magic nylon rope trick, slime and liquid nitrogen ice cream. These are all attention drawers when trying to do an outside event to get interest in chemistry.
The Magic Nylon Rope Trick
Jar with lid, glass rod with hooked end.
Solution "A" (0.5 M hexamethylenediamine ( H2N(CH2)6NH2, also called 1,6-diaminohexane) and 0.5 M sodium hydroxide in water),
Solution "B" (0.2 M sebacoyl chloride ( ClOC(CH2)8COCl ) in hexane).
How to make Solution A and B
Make solution "A" by placing a bottle of hexamethylenediamine in warm water to melt it (m.p. 39-40C). Dispense 6.0 g of the hexamethylenediamine into a bottle. Add 2.0 g of sodium hydroxide and add 100 mL of DI water to the bottle. Cap the bottle tightly and shake to dissolve and mix.
Make solution "B" by dispensing 2.0 g (1.6 mL) of sebacoyl chloride into a bottle, add 100 mL of hexane to the bottle. Cap the bottle tightly and shake to mix.
Now the magic can begin
1. Add 25-50 mL of solution "A" to the jar.
2. Place the glass rod in the center of the jar with the hook down.
3. Carefully pour the same volume of solution "B" as solution "A" down the glass rod, so as not to disturb the interface between the two solutions.
4. After solution "B" has been added, pull the glass rod out of the jar. The hook will snag the nylon that has formed at the interface of the two solutions.
5. Wrap the strand of nylon around the roller and wind the nylon strand onto the roller with a steady pace.
6. When you are done winding the nylon, close the jar to minimize the hexane fumes.
Chemistry behind the magic nylon rope trick
The word "nylon" is used to represent synthetic polyamides. The various nylons are described by a numbering system that indicates the number of carbon atoms in the monomer chains. Nylons from diamines and dibasic acids are designated by two numbers, the first representing the diamine and the second the dibasic acid . The nylon formed in this demonstration would be 6-10 nylon.
n H2N(CH2)6NH2 + n ClCO(CH2)8COCl [-NH(CH2)6NH-CO(CH2)8CO-]n + 2n HCl
Liquid Nitrogen Ice Cream
- 5 or more liters of liquid nitrogen and associated safety gear
- 2 quarts (1.9 liters) of Half and Half
- 1 cup (237 ml) of sugar
- 4 teaspoons (20 ml) of vanilla (optional)
- 2 cups (473 ml) of strawberries (or whatever flavor you like)
- wooden spoon
- wire wisk
- large plastic punch bowl
1. Mix the Half and Half, sugar and vanilla in a large plastic punch bowl with a wire wisk.
2. Add the flavoring. Wire wisk the mixture further if needed.
3. Pour a small amount (about 250 ml) of liquid nitrogen directly into the plastic punch bowl.
4. Stir the mixture with a wooden spoon. Be careful not to splash! (Make sure you have your gloves and goggles on)
5. Keep adding small amounts of liquid nitrogen until the mixture becomes too thick to stir.
6. Allow any excess liquid nitrogen to boil off before serving.
5 liters of liquid nitrogen should make two batches of ice cream.
Chemistry behind the ice cream
Liquid nitrogen is -320F or -196C. While liquid nitrogen is used for many temperature-related applications, it's particularly useful for freezing foods because nitrogen is odorless, colorless and tasteless. The secret to the creamy ice cream is all in the rapid freezing of the mixture. The liquid nitrogen causes the fat and the water particles to stay very small, giving the ice cream it's creamy consistency. The faster you freeze, the less you destroy tissue structures that could lead to a more rapid loss
Jar, lid and stirring rod
Borax Sodium tetraborate
PVA Polyvinyl Alcohol
How to make the Borax and PVA solutions
Both the PVA and the borax are sold as dry powders. Both need to be dissolved in water to make separate solutions. Use 40g of PVA for each liter of water, and 5g of borax per 100ml of water. This is enough for 20 people.
The PVA is the more difficult of the two to dissolve. If you have a magnetic stirrer/hot plate, you can simply heat the water to about 90oC, start the stir bar, and sprinkle in the powder. If you don't have a hot plate, don't attempt to mix the powder manually - it will take forever! Instead, you can use a crock pot at a low setting. Sprinkle in the PVA powder, stir, and cover. Stir again in a half hour, and every half hour or so until the powder is dissolved. When the PVA is completely dissolved, there will be no evidence of particles in the water. The particles are clear, so check for them under bright light.
To mix the borax solution, dissolve the borax in warm distilled water. Allow to cool, and transfer to a labeled storage bottle.
Let's make slime
1. Pour 50ml of PVA in jar can add color at this point
2. Add 5 ml of Borax while stirring
3. Place lid on jar and shake
Chemistry behind slime
This is what happens when a solution of Polyvinyl Alcohol (PVA) and a solution of Sodium Metaborate (Borax) are mixed together. Polyvinyl Alcohol is a repeating chain or polymer of the Vinyl Alcohol unit:
When the PVA is dissolved in water, the vinyl alcohol units link up to form chains of about 2,000 units! This results in a thick, syrupy appearance to the solution. When borax is added to the PVA solution, the chains of PVA cross - link to form a viscoelastic gel. The cross linking is weak, so the links continually form and break under the weight of the gel, or with handling. Leave a ball of the slime on a flat surface, and it slowly flattens out as the molecular chains slide over each other, rearrange themselves and reconnect. But if you pull suddenly on the material, it snaps.