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Sandy_dkk

Kemarin jam 01:36:12 PM
bukan rumit kang Farabi, tapi memang tidak bisa.

peterkusuma

Agustus 25, 2014, 10:03:23 PM
Teman2, ada yg tau kelarutan aluminium klorida dalam benzena ga?
Thx
 

Farabi

Agustus 25, 2014, 01:42:52 AM
Jadi penasaran, bisa ga tuh dipecahkan? Perkalian ya bukan pertambahan. Rumit banget kayaknya.
 

Sandy_dkk

Agustus 24, 2014, 11:58:59 PM
oh, ada yg nanya to d bawah? saya gak liat.
ada 3 variabel dan hanya ada 1 persamaan, maka mustahil mengetahui nilai setiap variabel. kecuali yang ditanyakan adalah hasil operasi dari variabel-variabel tsb, formula operasi tertentu masih mungkin ketemu hasilnya tanpa harus mengetahui nilai setiap v
 

Monox D. I-Fly

Agustus 24, 2014, 09:39:37 PM
bukannya 2p.3q.5r itu maksudnya 2p x 3q x 5r ya? Jadinya 1125000 = 30pqr
 

Sandy_dkk

Agustus 24, 2014, 04:04:27 PM
emang Farabi berpikir tentang apa?
 

Farabi

Agustus 21, 2014, 09:27:23 AM
2p+3q+5r totalnya ada 10 bagian. 2/10 *1125000 untuk p 3/10*1125000 untuk q dan 5/10 *1125000 untuk r. Gitu bukan? Yang kepikiran begitu.

keziakeren17

Agustus 18, 2014, 07:14:43 PM
gk ada yg mau jwb pertanyaan ku di topik
 

reborn

Agustus 18, 2014, 06:47:27 PM
@keziakeren17 bisa post di http://www.forumsains.com/fisika/ atau http://www.forumsains.com/fisika-smu/ ,. Selamat bergabung!

keziakeren17

Agustus 18, 2014, 06:39:36 PM
ada yg bisa bantu jwb soal fisika??

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Penulis Topik: Fact or Fiction : Glass Is a (Supercooled) Liquid  (Dibaca 4264 kali)

0 Anggota dan 1 Pengunjung sedang melihat topik ini.

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Fact or Fiction : Glass Is a (Supercooled) Liquid
« pada: Pebruari 28, 2007, 06:03:23 AM »
Gimana nih penjelasannya *lirik2 alinc  ::) jadi kaca/silica itu masuk kategori mana, benda padat apa benda cair?

Kutip
Fact or Fiction?: Glass Is a (Supercooled) Liquid
By Ciara Curtin

In medieval European cathedrals, the glass sometimes looks odd. Some panes are thicker at the bottom than they are at the top. The seemingly solid glass appears to have melted. This is evidence, say tour guides, Internet rumors and even high school chemistry teachers, that glass is actually a liquid. And, because glass is hard, it must be a supercooled liquid.

Glass, however, is actually neither a liquid—supercooled or otherwise—nor a solid. It is an amorphous solid—a state somewhere between those two states of matter. And yet glass's liquidlike properties are not enough to explain the thicker-bottomed windows, because glass atoms move too slowly for changes to be visible.

Solids are highly organized structures. They include crystals, like sugar and salt, with their millions of atoms lined up in a row, explains Mark Ediger, a chemistry professor at the University of Wisconsin–Madison. "Liquids and glasses don't have that order," he notes. Glasses, though more organized than liquids, do not attain the rigid order of crystals. "Amorphous means it doesnt have that long-range order," Ediger says. With a "solid—if you grab it, it holds its shape," he adds.

When glass is made, the material (often containing silica) is quickly cooled from its liquid state but does not solidify when its temperature drops below its melting point. At this stage, the material is a supercooled liquid, an intermediate state between liquid and glass. To become an amorphous solid, the material is cooled further, below the glass-transition temperature. Past this point, the molecular movement of the material's atoms has slowed to nearly a stop and the material is now a glass. This new structure is not as organized as a crystal, because it did not freeze, but it is more organized than a liquid. For practical purposes, such as holding a drink, glass is like a solid, Ediger says, although a disorganized one.

Like liquids, these disorganized solids can flow, albeit very slowly. Over long periods of time, the molecules making up the glass shift themselves to settle into a more stable, crystallike formation, explains Ediger. The closer the glass is to its glass-transition temperature, the more it shifts; the further away from that changeover point, the slower its molecules move and the more solid it seems.

Whatever flow glass manages, however, does not explain why some antique windows are thicker at the bottom. Other, even older glasses do not share the same melted look. In fact, ancient Egyptian vessels have none of this sagging, says Robert Brill, an antique glass researcher at the Corning Museum of Glass in Corning, N.Y. Furthermore, cathedral glass should not flow because it is hundreds of degrees below its glass-transition temperature, Ediger adds. A mathematical model shows it would take longer than the universe has existed for room temperature cathedral glass to rearrange itself to appear melted.

Why old European glass is thicker at one end probably depends on how the glass was made. At that time, glassblowers created glass cylinders that were then flattened to make panes of glass. The resulting pieces may never have been uniformly flat and workers installing the windows preferred, for one reason or another, to put the thicker sides of the pane at the bottom. This gives them a melted look, but does not mean glass is a true liquid.



adjie

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Re: Fact or Fiction : Glass Is a (Supercooled) Liquid
« Jawab #1 pada: Pebruari 28, 2007, 05:19:20 PM »
Aku rasa sifatnya sama seperti Hg. pada kondisi tertentu dia liquid, dan pada kondisi tertentu dia padat. Yah, sama dengan airlah..

Hmm.. mikir lagi.. ada jawaban lagi yang laen?

Offline reborn

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Re: Fact or Fiction : Glass Is a (Supercooled) Liquid
« Jawab #2 pada: Pebruari 28, 2007, 07:15:27 PM »
hmm... *pura2 mikir :P

nunggu ahlinya aja deh. Gw bener2 buta kimia :(

 

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