What is the material present at the tips of the nozzles for freon?

The correct answer is wax. In freon cooling systems, the tips of the nozzles are typically made of wax because it has specific thermal properties that allow it to effectively manage the flow of refrigerants, such as freon. The wax can melt or change state at certain temperatures, facilitating a controlled release of refrigerant or the adjustment of nozzle function in response to varying operating conditions.

In contrast, materials like plastic, metal, or rubber would not provide the same benefits. Plastic may not withstand the low temperatures associated with refrigerants, while metal might not have the appropriate flexibility or thermal response required for efficient operation. Rubber could also struggle with the extreme conditions and might degrade more quickly than wax in this context. Thus, wax is the optimal choice for ensuring effective and safe performance in freon nozzle applications.