Glass

[diane1]

Tonight in the car my son asked- what is glass made of? yikkes i remember doing something in school but did not want to get it all wrong so i said i'd ask my chums at answer bank - don't let me down now!

[ukkid76]

Sand

[Gef]

Glass is indeed made from sand. Most glass is what is known as soda-lime glass and is a complex mixture of silicon dioxide (silica) which comes from the sand, sodium silicate and calcium silicate. Other compounds can be added for specific uses eg lead oxide (for lead-crystal glass) and boron oxide (for borosilicate heat resistant glass known as Pyrex in the UK).

[whiskygalore]

Diane, I'd like to recommend ScienceNet to you. It is a free website and telephone helpline that is brilliant for answering all those questions asked by children, such as, "Why is the sky blue?". You just get in touch with ScienceNet, ask them the question, and they will email or call you with an answer in 'layman's terms'. They are fantastic. You can find them here: http://www.sciencenet.org.uk/

[ukkid76]

Another thing about glass is it's a liquid if you leave it long enough it would run in to a pool on the floor but you would have to leave it a long time though!!!!

[sddsddean]

Did you know, that the speed of a crack in glass is well over 3000mph.

[diane1]

I knew i could rely on you all, as i told my son all your answers he listened carefully then said -you must be the cleverest mum in the world!!!- made me feel great, thanks sooo much everyone.

[KARL]

It is correct to say that glass flows (you can see this in old glass which has been in the same window for many decades - refraction shows up ripples due to sag). However, I am not entirely certain that it would be correct to call it a liquid, rather that it is a plastic solid which changes shape under long term action of a force. It is an interesting phenomenon which can be seen in lots of solid materials, such as rocks, etc. The accumulation of infinitesimal increments (small enough not to cause a crack) over and over again through eons of time makes you stop in awe sometimes - just look at layers of rock each several metres thick which have been bent double a bit lice a stack of a few sheets of paper in out hands.

[KARL]

Isn't it amazing how you can misspell words when you rush to put your thoughts down: like becomes lice - something to do with brainwaves, perhaps adversely affected by gravity.

[Squirrel]

Or that our brains are made of glass? That would explain the sagging over time, and the mysterious way that they are often transparent to infomartion.

What does make some substances almost transparent, by the way?

[KARL]

A small afterthought: The way apparently immovable rock can be bent, completely against expectations, may serve as a very useful example in demonstrating to children how perserverence, patience, etc. can bear the most amazing fruit.