Final answer:
Soaps with a pH above 9.5 are highly alkaline and contain compounds that act as Brønsted-Lowry bases, resulting in a slippery feel. However, strong bases can be harmful to organisms and materials.
Step-by-step explanation:
Soaps containing a pH above 9.5 are considered to be highly alkaline. This high pH indicates that the soap contains compounds that act as Brønsted-Lowry bases, which accept protons from H₂O, creating an excess of hydroxide (OH-) ions.
This excess of OH- ions is what imparts the soap's basic characteristics and is responsible for the slippery feel often associated with soap solutions. It is important to note that like strong acids, strong bases can harm organisms and damage materials, such as causing burns to the skin or removing colors from cloth, hence the necessity for caution when using highly alkaline soaps.