For each of the following pairs of materials, decide which has the larger thermal conductivity. Justify your choices.

(a) Pure silver; sterling silver (92.5 wt% Ag7.5 wt% Cu)

(b) Fused silica; polycrystalline silica

(c) Linear and syndiotactic poly(vinyl chloride) (DP = 1000); linear and syndiotactic polystyrene (DP =1000)

(d) Atactic polypropylene ( = 106 g/mol); isotactic polypropylene ( = 105 g/mol)