среда, 31 августа 2016 г.

The Science Behind Edible Glass - Go Science Girls

The Science Behind Edible Glass - Go Science Girls
The Science Behind Edible Glass - Go Science Girls

How to make Edible Glass that really shatters

The idea for this activity came about when Jewel asked how glass is made. We explained that glass is made in a factory, where they get lots of tiny little grains of the purest sand, and heat it up until it is so hot that it becomes molten, and then it turns into glass.

But the questions kept coming. The next one was “What does molten mean?” We explained that molten is when something is so hot that it turns into a liquid. Different things become molten at different temperatures. Water becomes molten at 0oC. Sand needs a much higher temperature to become molten.

“But why doesn’t glass look like sand?” Hmm, that’s a trickier one to explain. Perhaps it’s easier to demonstrate. We’re not able to make actual glass in my own kitchen, but we can make a very close replica – edible sugar glass!

Homemade Edible Glass

Just like real glass, sugar glass is made from tiny opaque grains (of, in this case, sugar) which when molten and allowed to cool, transform into an amorphous transparent sheet, which is solid yet brittle. What does amorphous mean? We’ll get on to that later. First, let’s try making the stuff.

Try this science activity with 5-6 year olds and up. Jewel was 5 years, 2 months and Bumble was 2 years, 11 months old when we made this.

To make edible sugar glass, you need:

  • 1/2 cup caster sugar
  • 40ml glucose syrup (or corn syrup)
  • 60ml water
  • pinch cream of tartar
  • butter (or spray oil)
  • baking paper
  • cooking thermometer

The original recipe that we followed called for corn syrup, but that’s tricky to find in Australia, so we used glucose syrup instead. Since it’s mainly the water component which differs between these syrups, which will be boiled off anyway, I think you should be able to use either. You’ll also need some common household items like a large saucepan, spoon for stirring, baking tray, measuring spoons, etc.

What to do

1. Line a baking tray with baking paper, and grease with butter (or cooking spray).

2. Measure out the sugar, glucose syrup, water and cream of tartar into a large saucepan.

The kids can help with this bit. You might want to point out how the sugar looks like fine white (opaque) grains at this point.

Measuring out ingredients for edible glass

3. Slowly bring the mixture to the boil, until it reaches 150oC (300oF)..

This part is best done by an adult – firstly because 150oC is very hot. And secondly, because this part is not very exciting and requires a lot of patience. The key word here is to heat the mixture “slowly”. If you heat it too fast, it will start to caramelise and become yellow.

Once the water has boiled off, the temperature will start to rise. The amount of time this takes may vary – it’s more about the temperature reached than the time taken. A candy thermometer which clips onto the saucepan would be perfect, but Mr Banya used our

Drop the glass onto the baking paper, and watch it shatter into shards, just like real glass! (Be careful, some of those shards may be sharp enough to cut.) Taste it! It’s very sweet.

The science behind edible glass

6. Store any left over sugar glass in a sealed container in the fridge.

Because sugar glass is hygroscopic (meaning it attracts water from the surrounding environment), it will quickly soften and lose it’s brittle quality if exposed to humidity.

Plastic Container with shards of edible glass

Real glass is created by heating sand (which is mostly silicon dioxide) to 1700°C (3090°F). Wow, that’s really, really hot! When the molten sand cools, it transforms into a special kind of substance called an amorphous solid. Usually when things are solid, their molecules and atoms are arranged in an orderly structure. With amorphous solids, the molecules are arranged in a disorganised structure, which is more like the structure you’d usually find in a liquid. It’s this disorganised structure that makes amorphous solids transparent and brittle. You can simulate creating glass in your kitchen by melting sugar instead of sand. Molten sugar turns into another amorphous solid, called edible glass or candy glass, and has a glassy, translucent appearance.

How to make Edible Glass - fun science in the kitchen

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Original article and pictures take http://gosciencegirls.com/sugar-glass-edible-science-kids/ site

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