Explanation: In chemistry, substances are classified into three main categories based on their pH: acids, bases, and salts. Acids have a pH less than 7, bases have a pH greater than 7, and salts have a pH of 7 (neutral). The pH scale is a logarithmic scale used to specify the acidity or basicity of an aqueous solution.
Bases are characterized by their soapy and slippery feel. This property is due to the presence of hydroxide ions (OH-) in the solution. When a base is dissolved in water, it dissociates into hydroxide ions and a positive ion. The hydroxide ions are responsible for the soapy feel and the ability of bases to neutralize acids. Bases can be strong or weak, depending on the extent of their dissociation in water.
Acids, on the other hand, have a sour taste and can be corrosive. They are characterized by the presence of hydrogen ions (H+) in solution. Acids can also be strong or weak, depending on the extent of their dissociation in water. Acids do not have a soapy feel and are not slippery to touch.
Salts are the products of neutralization reactions between acids and bases. They do not have a soapy feel and are not slippery to touch. However, some salts can be used in soaps and detergents, but the soapy feel is due to the base component, not the salt itself.
Minerals are naturally occurring inorganic substances and do not have a soapy feel. Some minerals can be used in soaps and detergents, but the soapy feel is due to the base component, not the mineral itself.
In summary, the substances that are soapy to touch are bases. This is because bases have a pH greater than 7 and are characterized by their soapy and slippery feel due to the presence of hydroxide ions in solution. This property is distinct from acids, salts, and minerals, which do not have a soapy feel. Understanding the properties of acids, bases, and salts is crucial for various applications in chemistry, including the formulation of soaps and detergents.