Question

Focusing on the bonds, explain how glass becomes softer when heated.

1) Stronger bonds break first, causing glass to soften gradually.
2) Weaker bonds break first, causing glass to soften gradually.
3) As the glass is heated the length of the bonds increases.
4) The longer bonds break first.
5) Stronger bonds gain energy when heated causing them to break quickly, which leads to softer glass.

Answer 1

Glass softens when heated due to the gradual breaking of weaker bonds before the stronger ones, leading to a range of softening temperatures. Amorphous materials like glass have variable bond strengths, so as thermal energy increases, these weaker bonds break, causing softening over a broad temperature range.

Step-by-step explanation:

When glass is heated, it becomes softer due to the breaking of its weaker bonds first, allowing it to soften gradually. This process occurs because glass is an amorphous solid, which means its molecules are not all equivalent in structure, causing a variety of different bond strengths within the material. During heating, the addition of thermal energy increases vibrational motions of atoms.

The weakest intermolecular attractions break first with the increase in temperature, and as the heating continues, the stronger bonds also start to give way. This results in a wider range of temperatures over which the material softens, rather than a single melting point as seen with crystalline solids. In contrast, items such as Pyrex®, which have a small coefficient of linear expansion, are less susceptible to thermal stress and breakage because the material expands and contracts less when subjected to changes in temperature.