Airdate: Nov 02, 2010
Scientist: Dr. Daniel A. Savin
Material Science - Silly Putty
Silly Putty - is a liquid or a solid?
You remember Silly Putty a science toy we all grew up with. Would you say it's a liquid or a solid? I'm Jim Metaner and this is the Pulse of the Planet. Daniel Savin is an assistant professor at the University of Southern Mississippi.
DS: So what happens to the silly putty when I drop it? It bounces back up to my hand. So over short times it behaves like a solid.
DS: But I can also take the silly putty and I can start to stretch it out like taffy. And if I stretch it out like taffy slowly it'll just keep stretching as long as I'm pulling. But if I take the same silly putty and I rub it back together and I pull on it quickly, what do you think is gonna happen? It breaks in 2 pieces. So it behaves like a solid over short times but it behaves like a liquid over long times. In fact I could take these 2 edges and put them back together and I could start to pull on it again. And it doesnâ€™t break it behaves as if that break never happened.
DS: Silly putty like all polymers behaves differently over different time scales. We're gonna take some pieces of the silly putty, and we're gonna hit it with a hammer and we're gonna see what happens. So Silly behaves like a solid over short times - What do you think would happen if you took an ice cube and hit it with a hammer? Well it would probably do the same thing. But could you take an ice cube and form it into a ball and have it be a nice rubbery ball that bounces? And then stretch it out? You certainly would not be able to do that with ice but this is something you can do with polymers.
Besides Silly Putty, there are many kinds of polymers with many different special properties and they're all part of the palette of materials that a materials scientist works with. Materials science is one of the science topics in this year's Kids Science Challenge our free nationwide competition for 3rd to 6th graders; check out kidsciencechallenge.com. Pulse of the Planet is made possible by the National Science Foundation. I'm Jim Metzner.