The organ that primarily uses chemical digestion and absorption of food is the small intestine.

Here's why:

* Chemical Digestion: The small intestine receives partially digested food from the stomach. It then uses enzymes secreted by the pancreas and the lining of the small intestine itself to break down carbohydrates, proteins, and fats into smaller molecules that can be absorbed.

* Absorption: The small intestine has a large surface area due to folds, villi, and microvilli, which maximize the absorption of nutrients into the bloodstream.

While the stomach and mouth also play a role in digestion, their primary functions are mechanical breakdown and initial chemical digestion. The small intestine is where the majority of the absorption occurs, making it the key organ in the digestive process.