3.5. (a) What is the fictive temperature of a glass?

(b) Why do glasses have coefficients of expansion more like liquids above the fictive temperature and more like crystalline solids below the fictive temperature?

(c) What would you predict would happen to the fictive temperature of a silica if a function of Na₂O content, NaF content?

3.6. (a) If you were asked to obtain a glass (liquid) at 800C with the highest mole percent silicon dioxide and you were restricted to only one other oxide in addition to silica, what additional material would you choose? Give an explanation.

(b) Why does quartz melt at a temperature below the melting point of crystobalite?