Cracking when heating the cold

[ramdisc]

Hello,

 

You know how you go to the refrigerator and take out the bottle of ketchup and it is cold and sealed tightly? So you think a little warm water would ease it. When you turn on the tap and stick the bottle neck onto the warm water, the bottle neck cracks!

 

Here are my questions:

 

1. What is the term to describe this?

 

2. Why does this happen?

 

3. Can it happen vice versa? Say I stick a very hot stick of tempering metal into the ice-cold water as opposed to room temperature water. Would it crack!?

[YT2095]

Here are my questions:

 

1. What is the term to describe this?

 

2. Why does this happen?

 

3. Can it happen vice versa? Say I stick a very hot stick of tempering metal into the ice-cold water as opposed to room temperature water. Would it crack!?

 

1. Bad Luck.

2. Expansion, when things are cold, they shrink a little, when you warm them, they expand. Now if the Outside of the bottle is warmed and expanding but the heat hasn`t gotten to the inside of the glass equaly, you can see how a pressure or tension is built up, this can be enough to break the glass, it`s way of releiving this pressure.

3. it sure can, it`s the same as in point 2 but in reverse, but for metals it`s less likely to occur, infact this principal is an advantage with some metal treatment procedures, I wouldn`t try it with Glass though!

[vrus]

Hello' date='

 

You know how you go to the refrigerator and take out the bottle of ketchup and it is cold and sealed tightly? So you think a little warm water would ease it. When you turn on the tap and stick the bottle neck onto the warm water, the bottle neck cracks!

[/quote']

 

I think it is called unequal expansion of solids. Honestly, I don't know how it happens, but I think it could be because there is such a large temperature change and since the glass is a bad conductor of heat, in the warmed region, molecules are gaining lots of KE much faster than the others causing a large fluctuation in energy levels. Can someone confirm this pls. ?

[dttom]

2) When matter is heated, it almost expands, while when matter is cooled, it almost contracts. The phenomenon described by you can be explained by this theory: matter took out from the refrigerator, particles in it are mostly contracted, but when it is suddenly put into warm water, those particles inside will be suddenly expanded, this probably destructs its original structure, thus cracked.

3) I'm not sure about that, but I think it should be reversible, that is, when matter with a fixed structure is heated to a very high temperature, and is suddenly inserted into icy water, then the highly expanded matter will contract in a few second, suring the contraction, if its structure is broken, it cracks.

[mezarashi]

Heat like most other physical processes must diffuse into or out of a material. Cracking occurs when the temperature gradient along the cross-section of a material is great enough to produce strains beyond the material's elastic range.

 

Metals generally won't crack because they allow very large strains (they are very elastic), and also have a yielding range where they tend to deform rather than fracture.

[YT2095]

maybe I`m wrong here, but aren`t the last few posts just a rehash of what I said in the 1`st place?

[mezarashi]

maybe I`m wrong here, but aren`t the last few posts just a rehash of what I said in the 1`st place?

 

Not including the ambiguous "unequal expansion of solids" theory and the "large fluctuation in energy levels" idea, I would agree. I just wanted to put it in more scientific terms ^^