Question

Which of the following elements are commonly added to sand when making glass, to improve its thermal properties? Select all that apply.

a) Sodium (Na)
b) Calcium (Ca)
c) Aluminum (Al)
d) Boron (B)

Answer 1

When making glass, Sodium (Na) is added to reduce the melting point, Calcium (Ca) is added for hardness and durability, and Boron (B) is included for superior thermal shock resistance, making borosilicate glass particularly resilient.

Step-by-step explanation:

When making glass, certain elements are added to sand to improve its thermal properties. These include:

• Sodium (Na) - Often added in the form of sodium oxide (Na2O) to lower the melting point and ease the glassmaking process.
• Calcium (Ca) - Typically added as calcium oxide (CaO), it improves the hardness and durability of the glass.
• Boron (B) - Borosilicate glasses, which contain boron, are noted for their excellent resistance to thermal shock and high-temperature durability.

Aluminum (Al) is not commonly added with the primary intent of improving thermal properties but may be present as a minor component in some glass compositions. The addition of boron, specifically, results in borosilicate glass, which is especially resistant to cracking or shattering under extreme temperature changes. This type of glass is used in applications requiring a high degree of thermal resistance.