**Adsorption:**

Adsorption is a surface phenomenon in which particles or molecules from a gas, liquid, or solution adhere to the surface of a solid material. It occurs when the attractive forces between the adsorbate (the substance being adsorbed) and the adsorbent (the material on which adsorption occurs) are stronger than the cohesive forces within the adsorbate. The process of adsorption is usually accompanied by a decrease in the entropy of the system.

**Types of Adsorption:**

1. Physical Adsorption (Physisorption): In physical adsorption, the adsorbate is held onto the surface of the adsorbent by weak van der Waals forces. It is reversible and occurs at low temperatures. The adsorbent-adsorbate interaction is non-specific, and multiple layers of adsorbate can be formed.

2. Chemical Adsorption (Chemisorption): Chemical adsorption involves the formation of chemical bonds between the adsorbate and the adsorbent surface. It is a highly specific process and occurs at higher temperatures. The adsorption is usually irreversible, and only a monolayer of adsorbate is formed.

**Applications of Adsorption:**

- Adsorption is widely used in processes such as gas purification, water treatment, and separation of mixtures.
- Activated carbon is commonly used as an adsorbent to remove impurities and contaminants from gases and liquids.
- Adsorption is also utilized in chromatographic techniques for the separation and analysis of compounds.

**Absorption:**

Absorption refers to the process in which one substance is taken up or dissolved by another substance. It involves the penetration and assimilation of the absorbed substance throughout the bulk of the absorbent. Unlike adsorption, absorption occurs in bulk rather than just at the surface.

**Types of Absorption:**

1. Physical Absorption: Physical absorption, also known as dissolution, occurs when the absorbed substance is taken up by the absorbent without any chemical reaction. The absorbed substance remains in its original molecular form within the absorbent.

2. Chemical Absorption: Chemical absorption involves a chemical reaction between the absorbed substance and the absorbent. The absorbed substance undergoes a chemical transformation, resulting in the formation of new compounds.

**Applications of Absorption:**

- Absorption is commonly observed in biological processes, such as the absorption of nutrients by cells in the human digestive system.
- It is utilized in various industrial processes, including the absorption of gases in scrubbers for air pollution control.
- Absorption is also important in pharmaceutical formulations, where drugs are absorbed by the body to exert their therapeutic effects.