Yes, according to the provided reference, soap is a mixture.
The reference lists the following as mixture substances: Sugar solution, Air, Soil, Coal, Blood, and Soap. The reference specifies that these mixture substances "can be compounds or elements which can have a variable composition." This is consistent with the definition of a mixture.
In essence, soap is created through a chemical process (saponification) that combines fats or oils with an alkali, such as lye. However, the resulting soap product isn't a single, pure substance. Instead, it's a blend of different fatty acid salts, along with other components depending on the specific formulation (e.g., glycerin, water, fragrances, colorants). Because the composition can vary, soap fits the definition of a mixture as outlined in the reference.
