Which of the following properties of a sand mold helps to avoid cracking when in contact with molten metal?

Thermal stability is a crucial property of a sand mold that helps prevent cracking when in contact with molten metal. When molten metal is poured into a mold, it experiences a significant temperature contrast. The sand mold must be able to withstand these high temperatures without deforming or breaking apart. If the mold does not have adequate thermal stability, it can become weakened or fail, leading to cracks that can compromise the integrity of the mold and affect the final casting.

Thermal stability enables the mold to maintain its structural integrity under extreme conditions, ensuring that it doesn’t expand or contract excessively, which can lead to the development of cracks. Thus, this property is essential for ensuring a successful casting process.

In contrast, while permeability allows gases to escape during the pouring process, and strength contributes to the mold's ability to hold its shape, they do not specifically address the issue of thermal stress that can lead to cracking. Reusability is also important for cost-effectiveness but does not directly relate to preventing cracks during the heat-induced stress of the casting process.