DIY experiments are a great, hands-on way to get your kids excited about science. Instead of giving them a dusty old textbook full of abstract scientific concepts they may not understand, learning through experiments lets them see for themselves how ideas translate to reality.
If your child is always asking where things come from, a few experiments in engineering can illuminate the answers while giving you an afternoon of fun together. Plastics engineering, for example, utilizes a lot of concepts that you can easily illustrate using things you already have at home, so you can learn all about where everyday objects like plastic baggies, shower curtains, beach balls and inner tubes come from. You don’t have to visit an industrial manufacturing plant to try your hand at plastics engineering-with a few simple at-home experiments like these, you’ll be melting and melding like a pro!
Hot Air Welding
What you need: Cellophane wrap, cookie, hair dryer
When manufacturers use hot air welding to meld plastics together, they blast them with a concentrated stream of extremely hot compressed air. If you want to show your child what compressed air is, you can buy it by the can at office supply stores-domestically, it’s often used to clean out keyboards and circuitry. Otherwise, you could use a bike tire pump or a car tire air kiosk at the gas station. Because you can’t heat compressed air like they do in the hot air sealing plant, though, you’ll be demonstrating a less-refined version of the process.
Place a cookie on a large, rectangular piece of cellophane. Fold the cellophane over itself, over the top of the cookie, like a book. Then, hold your hair dryer a few inches over the cellophane and turn it on. As you move it over the cellophane, the plastic wrap will heat up, shrink and melt-since it is folded over on itself, the plastic will melt together, forming a seal around the cookie. This is how hot air welding works, although it is much more precise than your hair dryer!
RF Welding
What you need: One large jar, two types of colored sand, one spoon, two plastic knives, rubber cement
Radio frequency heat sealing, or RF welding, is a process that uses high frequency waves to alter the molecular structure of two pieces of plastic. While you can’t imitate this process at home, you can conduct a simple demonstration to teach your child about molecules, how they make up matter and how they can be altered to create new matter.
Begin with an empty jar and two types of colored sand. Explain that each grain of sand represents a molecule, which is a tiny, microscopic building block that is found in everything. A molecule by itself is very small, but when enough of them are together in one place, they make a whole. Pour one of your colored sands into the jar-they represent the molecules in a single piece of plastic.
Pour your other colored sand into the jar. It should sit right on top of the other one, without the grains mixing. This colored sand represents a different piece of plastic-the two can touch, but their molecules are going to stay separate.
Finally, stick your spoon into the jar and start swirling it around. The spoon is a high frequency wave, which passes through the plastics and mixes up their molecules. As you swirl the spoon around, it should mix up the two colored sands until they are completely mixed together, and you can pull out the spoon. Explain that the molecules are so mixed up that they can never come apart-like the grains of sand, there are too many, and they’re too small for you to separate them. You have combined them, creating something totally new that didn’t exist before: A solid structure, with a whole new molecular composition.
Solvent Bonding
You can use the sand experiment to explain how solvent bonding works, too. When plastic manufacturing companies use solvents to join plastics, they are performing a process similar in spirit to RF welding. The solvent is applied to the materials, which it superficially melts. As they melt, they are pressed together, and the molecules rearrange together in a process spiritually similar to RF welding and your sand experiment.
You may explain how these solvents are different from domestic solvents by using rubber cement to attach two pieces of plastic. Smear rubber cement on two plastic knives and press them together. When it sets, you can demonstrate that they are stuck together, but by assertively pulling them apart, they split. You can even peel the dried rubber cement right off. Compare that to the irreversibly-mixed jar of multicolored sand, and you can demonstrate that household glues simply create a sticky layer that can be removed, while chemical solvent binding actually rearranges the molecules of the materials and blends them together.
More Science Resources
Making At-Home Experiments Fun and Easy!
- National Geographic Kids
- Simple experiments you can perform at home
- RF Welding
- More information about plastic engineering
- PBS Zoom
- Experiments in engineering for kids
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