Question

What describes only a physical change during digestion?

A: Hydrochloric acid in the stomach breaks down proteins.
B: Chewing in the mouth breaks food into smaller pieces.
C: Enzymes in saliva start the digestion of starches before food is swallowed.
D: Bacteria in the intestines convert dietary fiber into fats.

Answer 1

Chewing in the mouth breaks food into smaller pieces represents only a physical change during digestion, as it is a mechanical process with no chemical alteration of the food.

Step-by-step explanation:

What describes only a physical change during digestion? The correct answer is B: Chewing in the mouth breaks food into smaller pieces. This is because chewing, also known as mastication, is a mechanical process that does not chemically alter the structure of the food. It's an important first step in the digestion process, making it easier for the body to subsequently digest and absorb nutrients. Unlike the other options, chewing doesn't involve chemical reactions; hydrochloric acid and enzymes such as pepsin contribute to chemical changes, breaking down food on a molecular level, which is not a mere physical change.

Answer 2

B: Chewing in the mouth breaks food into smaller pieces. describes only a physical change during digestion.

Step-by-step explanation:

B:Chewing in the mouth breaking down food into smaller pieces is the only option that describes a physical change during digestion. Physical changes involve alterations in the physical state or appearance of a substance without changing its chemical composition. Chewing mechanically breaks down large food particles into smaller ones, increasing the surface area for enzymatic action but without altering the chemical composition of the food.

Option A involves a chemical change as hydrochloric acid breaks down proteins into simpler molecules. Option C also describes a chemical change as enzymes in saliva initiate the digestion of starches into simpler carbohydrates.

Option D mentions the conversion of dietary fiber into fats by bacteria in the intestines, which is a biochemical process involving the transformation of one chemical compound into another. Therefore, option B is the only one that specifically represents a physical change in the digestive process.

Understanding the distinction between physical and chemical changes during digestion is essential for grasping the complex processes involved in breaking down food for nutrient absorption. Physical changes, like chewing, play a crucial role in increasing the efficiency of chemical digestion by providing a larger surface area for enzymes to work on, facilitating the overall digestive process.