Final answer:
The duodenum is the first part of the small intestine where chemical digestion occurs.
Step-by-step explanation:
The duodenum is the first part of the small intestine, directly connected to the stomach. It is also the shortest part of the small intestine, averaging only about 25 cm (10 in.) in length in adults. Its main function is chemical digestion, and it is where most of the chemical digestion in the entire GI tract takes place.