Question

How do you say that the process of digestion is a chemical change.

Answer 1

because in digestion the HCL hydrochloric acid break all the nutrients into its simplest form like protein into amino acids

but amino acids can't be converted into protein again

in digestion the oxygen burns the food and a gas name the CO2 is released these all are the feature of chemical change

Answer 2

The process of digestion is a bio-chemical change because it involves enzyme pepsin (pepsinogen in its inactive form) and the action of hydrochloric acid......
Carbohydrates to glucose,
protein to amino acid and
fats to fatty acids and glycerol are the end products of digestion....
As in a chemical reaction new substances are formed in this also new products are formed....
Hence it is a chemical change.