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Q.

Why glass when heated cracks while metal does not ?

Tags: travel, heated cracks
Asked by raju, 01 Feb '13 12:54 pm
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Answers (9)

1.

The reason is because glass is heated up sand, where as metal is an ore, so when u heat u glass, it attempts to become its original state.
Answered by LIPSIKA, 01 Feb '13 12:58 pm

 
  
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2.

When the glass is heated the inner surface of the glass gets the heat first and expands more quickly than the outside. The pressure from this heated, expanded inside surface is so strong and so sudden as it hits the outside of the glass that the whole glass breaks.
Answered by ajay, 01 Feb '13 01:01 pm

 
  
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3.

Glass is a poor conductor of heat, but will expand upon heating. The combination of these two things means that if glass is heated quickly, it will develop stresses and may crack.
The glass used on stove tops is special glass with a low coefficient of expansion, so one of the danger factors above is missing.
Glass used as laboratory ware is often very thin, or made glass with a low coefficient of expansion.
Another technique used to make glass more heat-resistant (e.g. cups and pans) is to pre-stress it (tempered glass) so that the surface is under compression, and thus resistant to cracking.

Metal on the other hand, is not usually subject to brittle fracture, and it is usually a good conductor of heat.
Answered by anil garg, 09 Mar '13 08:46 pm

 
  
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4.

The reason is because glass is heated up sand, where as metal is an ore, so when u heat u glass, it attempts to become its original state.
Answered by Quest, 25 Feb '13 08:18 pm

 
  
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5.

Thin glass warms up more quickly because it IS thin and not subject to differences in temperature within the glass itself that cause internal stress. With thick glass, the surface may be hot, but the center may still be cold, and the difference in temperature will cause it to shatter or crack.
Answered by saranathan Narasimhan, 01 Feb '13 02:35 pm

 
  
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6.

This happens if proper Annealing is not done.
Answered by amitava duttamajumdar, 01 Feb '13 02:17 pm

 
  
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7.

As glass is a bad conductor of heat, only the affected portion gets heated, and hence expands, whereas that area which doesnot have direct contact with heat, doesnot expand, giving rise to tension in surface leading to cracking, whereas metals are good conductors of heat, and hence the whole metal gets equally heated, and expanded so there is no surface tension
Answered by rajnikant raiyarela, 01 Feb '13 01:06 pm

 
  
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8.

The atoms become free and collide with each other causing breaking of glass. in case of butter, it melts. however, glass melting temperature is above 1400 deg c.
Answered by Manoj M, 01 Feb '13 12:59 pm

 
  
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9.

The reason is because glass is heated up sand, wheras metal is an ore, so when u heat u glass, it attempts to become its origonal state
Answered by iqbal seth, 01 Feb '13 12:56 pm

 
  
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