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Expert-verified Found in: Page 359 ### Physics Principles with Applications

Book edition 7th
Author(s) Douglas C. Giancoli
Pages 978 pages
ISBN 978-0321625922 # Question 12: The principal virtue of Pyrex glass is that its coefficient of linear expansion is much smaller than that for ordinary glass (Table 13–1). Explain why this gives rise to the higher heat resistance of Pyrex.

Pyrex glass has a much higher heat resistance than ordinary glass because it expands less on heating. Thus, the chances of breaking get reduced.

See the step by step solution

## Step 1: Linear expansion

Most of the solid substances linearly expand on heating. When the temperature of a solid object of length $${l_0}$$ is increased by$$\Delta T$$, the length of the object increases by $$\Delta l$$ amount.

The change in the length of the object is given as:

$$\Delta l = \alpha {l_0}\Delta T$$

Here, $$\alpha$$ is known as the coefficient of linear expansion.

The coefficient of linear expansion of Pyrex glass is $$3 \times {10^{ - 6}}\;{\left( {{\rm{C}}^\circ } \right)^{ - 1}}$$, and ordinary glass is $$9 \times {10^{ - 6}}\;{\left( {{\rm{C}}^\circ } \right)^{ - 1}}$$.

## Step 2: Explanation for the higher heat resistance of Pyrex

The value of the coefficient of linear expansion of Pyrex glass is much smaller than that of ordinary glass. Thus, on heating, the expansion in ordinary glass will be much more than the Pyrex glass. Therefore, when heated rapidly, much higher thermal stress will develop in the ordinary glass, and thus there will be more chances of crossing the breaking stress. So, there are more chances of the ordinary glass breaking as compared to the Pyrex glass when heated rapidly.

Thus, you can say that Pyrex glass will not easily break when heated to a higher temperature. Therefore, the heat resistance of Pyrex glass is much higher than that of ordinary glass. ### Want to see more solutions like these? 