Step-by-step explanation:
Sodium stearate , is the soap , it a ionic compound , hence , can easily break to cation and anion , and therefore is soluble in water .It works on the principle of micelle formation .
Tristearin and stearic acid are fatty acids , and have are carboxyl group and have a very huge hydrocarbon chain , making it non polar in nature ,hence is is insoluble in water , since , water is a polar molecule .