Why does heat make objects break?

[albert.mck]

Homework Statement

I need to proove that temperature changes make objects break. I used a stone, and heated it for about 10 minutes. After that I put it in cold water. According to my teacher that should've broken the stone, but it didn't. I had to give it a few hits, not too many or too strong, with a hammer until it broke in half. Why does this happen? I know it's because it expands and then contracts too fast, but I don't know what physical terms I need to use or a physical explanation.

 

[berkeman]

Homework Statement

I need to proove that temperature changes make objects break. I used a stone, and heated it for about 10 minutes. After that I put it in cold water. According to my teacher that should've broken the stone, but it didn't. I had to give it a few hits, not too many or too strong, with a hammer until it broke in half. Why does this happen? I know it's because it expands and then contracts too fast, but I don't know what physical terms I need to use or a physical explanation.

Welcome to the PF.

What research and reading have you done on this so far? I would start with a Google search using terms like Thermal Stress Fracture Crack Brake, and so on. Let us know what you find...

 

[albert.mck]

I found that it happens when a thermal gradient causes different parts of the object to expand by different amounts. And that the stress of the expansion may overcome the strength of the object, causing a crack to form.
But I still don't get why it causes it to break. Or what is the "stress of the expansion"

 

[Nidum]

https://www.google.co.uk/search?q=thermal+shock+&ie=utf-8&oe=utf-8&gws_rd=cr&ei=XUE1Vv_fJoKwa8GDrYAB