MCQ Detailed View

Blotting paper is a highly porous material designed to quickly absorb and retain liquid. The main physical process responsible for this absorption is known as capillary action. Capillary action occurs when a liquid moves upward or through narrow spaces in porous materials without the assistance of external forces and sometimes even against gravity. This is caused by the combined effects of cohesive forces between liquid molecules and adhesive forces between the liquid and the solid surface.

When blotting paper comes into contact with a drop of liquid, the adhesion between the liquid molecules and the fibers of the paper allows the liquid to spread. At the same time, cohesion among liquid molecules helps pull more liquid into the narrow pores of the paper. The small diameter of the capillaries in the blotting paper fibers enhances this effect, allowing the liquid to rise or spread rapidly.

Other options are not correct:

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  Surface action is a general term and does not specifically explain the absorption process.

  
  


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  Viscosity refers to the internal resistance of a liquid to flow and is unrelated to how blotting paper absorbs liquids.

  
  


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  Boldness has no scientific relevance to liquid absorption.

  
  

Capillary action is a well-known phenomenon not only in blotting paper but also in various natural and industrial processes. For example, it is responsible for the upward movement of water in soil and in plant roots and stems. In laboratories, capillary action is utilized in paper chromatography for separating mixtures based on solubility.

In physical chemistry, understanding capillarity is essential because it explains how liquids interact with solid surfaces, wetting behavior, and the effects of surface tension in narrow tubes or porous substances. Blotting paper is a simple, everyday example of this important physical phenomenon.