Silica sand is the most commonly used mineral for molding and core making applications in foundry technology due to its availability, thermal and chemical attributes. However, there are many additional requirements foundry sands need to meet regarding their sizing, chemical purity, physical durability and thermal properties. This research studies the thermophysical properties of a foundry silica sand comprehensively. After separating one sand batch into numerous grain size ranges, the chemical composition and thermophysical properties of the fractions were investigated, respectively. By means of this approach, the chemical properties and thermal behavior can be directly linked. The silicon dioxide content shows a strong correlation with the thermal expansion properties of the various fractions. The results give a better understanding of the high temperature behavior of foundry silica sands and clarify the role of factors affecting their thermophysical properties.