Final answer:
The substance that all detergents contain to reduce surface tension between soil and the surface to be cleaned is known as a surfactant, which is the correct answer (A) to the question.
Step-by-step explanation:
All detergents contain a surfactant that reduces surface tension between the soil and the surface being cleaned. The correct answer to the question is A) Surfactant.
Surfactants or surface-active agents are a group of chemical compounds that disrupt the attractive intermolecular interactions between the molecules of a liquid, such as water. This action significantly reduces the surface tension of the water, which allows the surfactant molecules to interact with both hydrophobic substances, like oils and grease, and hydrophilic substances, like water. This is critical in the cleaning process, as it enables the detergent to emulsify and dissolve dirt, facilitating its removal.
In laundry detergents, surfactants absorb and emulsify soil into the water. By reducing the surface tension, they enhance the wetting of the fabric, which helps lift dirt off and disperse it in water, preventing soils from re-depositing onto clothing.
Hand dishwashing detergents also utilize surfactants for their primary cleaning role. Their ability to lower the surface tension of dishwashing water improves the solubility of modern surfactant mixtures and allows water to run off dishes quickly, facilitating the drying process.