Question

Question: Thermal stresses caused by uneven cooling can easily break glass cookware. Explain why Pyrex®, a glass with a small coefficient of linear expansion, is less susceptible.

Short answer

Answer

Pyrex®, a glass with a small coefficient of linear expansion, is less susceptiblebecause the difference between the expansion in various parts of the cookware is minimum. These are made of borosilicate, which has higher thermal resistance makes them better for cooking work.

Step-by-step solution

Thermal expansion and stress

Thermal expansion is the increase or decrease of the body when there is a temperature change. And a constrained normal expansion creates thermal stress.

Thermal stress is the defect or internal reallocation of forces within an object due to a significant temperature variation. A thermal distribution may or may not be invariant, depending on the nature of the loading condition.

The coefficient of linear expansion

The coefficient of linear expansion is related to a change in a shape or dimensions of a solid body with a temperature change. When heat is applied to glass cookware it expands because it is a good conductor of heat and it tends to break easily.

Here, we are discussing Pyrex glasses. These are tempered glass and have more strength. And the glass with a small coefficient of linear expansion is less susceptible to breaking due to the difference between the expansion in a different part of the cookware is minimum.

Therefore, Pyrex does not shrink at the same pace as conventional glass due to its low coefficient of thermal expansion, hence the effects of uneven cooling are less noticeable.