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Hotchalk Global

news & tips

A collection of helpful articles on teachers and teaching

Amazing Glass

A friend sent me a You Tube video on the future applications of glass that sent my head spinning. From the touch screens of the new tablets to walls that adjust to light to tables that interact the future of this material is deeply immersed in technology applications.

First, glass is good old silicon (the2nd most abundant element in the Earth’s crust) with oxygen (the most abundant element). Most of the glass we encounter in daily life is about 75% silicon dioxide, SiO2. The new glass materials can have a host of other chemicals as the backbone and lots of other additives. The key is that the material to be called glass is a solid that is non-crystalline in structure and goes through a glass transition when heated. A glass transition is a fancy way of saying that the material goes from being hard and brittle to being softer and more rubbery.
Most glass has soda lime (from limestone) in it to lower the glass transition temperature. But, the glass folks can add lead and other metals to increase the refractivity of glass. This makes the glass appear more brilliant. Think about cut glass here to get the idea. They use thorium oxide and other compounds to produce high quality lenses.
Once the glass is chemically produced they can add surface materials to improve the strength or to alter the appearance. They put some treatments inside the glass of autos and bank teller windows to make them stronger even to the point of bullet proof in the banks. That makes glass pretty versatile. To make it stronger they put glass through a heating and cooling process called annealing.

To show kids in the classroom what annealing is you can use a simple Bunsen burner and a common bobby pin. This process is detailed well at the Chemical Education site from Wisconsin.

This heating and cooling is a great way to show that the atomic structure of materials is important. With one structure the metal in a bobby pin breaks easily and with another it is soft and flexible. Then yet another treatment and the pin becomes strong and springy. For most students it is tough to imagine the atomic level of atoms lining up in different ways for different purposes. In this lab I have my students draw what they think the structure might look like in the 3 different bobby pin treatments. We compare them to sites on the web and that is a great place to begin a discussion about using simple materials for more complex applications and that leads us to glass.
There is a description of a new glass used in lasers developed by NASA at this site.

There is a museum of glass run by the folks at Corning with an interesting site. At this site go to “collections” then “glass innovations center” to find a game that does a very nice job of connecting chemistry to glass making.

Glass is something that every student will have encountered and there are lots of misconceptions about this ubiquitous material. The final piece in this post is the link to the video that made me think of glass in a thousand different ways. This is technology fused with materials science and powerful.

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