Video title: What is glass made of?
This is the biggest glass building in the world.
It's the Crystal Cathedral, in California.
Crystal Cathedral
California, USA
It has over 10,000 glass windows.
But what is glass made of?
What is glass made of?
Most glass is made from three raw materials that must undergo a chemical reaction or change.
Rough grains of silica sand...
silica sand
The white powder sodium carbonate...
sodium carbonate
And the soft white solid lime, also called calcium carbonate.
lime
calcium carbonate
The three raw materials of glass are then mixed together to form a grey lumpy powder.
Only when heated to a very high temperature, of about 1400 degrees Celsius, do they chemically react together to produce glass.
1400°C
Reactions that absorb heat are known as endothermic reactions.
endothermic reactions
absorb heat
Glass has many properties that are very different to those of its ingredients ... sand, sodium carbonate and lime.
Glass has a smooth texture.
It's transparent, meaning you can see through it.
transparent
It can be coloured with dye to produce stained glass.
When hot it can be moulded into many different shapes.
But when it cools it becomes rigid and smashes easily.
The properties of glass make it ideal for many uses, from fish tanks...
To magnifying glasses...
Bottles...
To buildings.
It's thanks to its transparent properties that the architect chose it as the building material for the Crystal Cathedral.
Glass lets in so much sunlight that during the day there's no need for the cathedral to use any electric lights.
Chemical reactions can change the properties of materials.
We use glass every day, but how is is made?
Learning points
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