Question

Which of these is not a chemical reaction?

• A. Digestion of food
• B. Baking of a cake
• C. Tearing of paper
• D. Fermentation of grapes

Answer 1

The correct option is C

Tearing of paper

Explanation for the correct option:

1. Physical change: A change where no new substances are formed, and can be reversed easily is called physical change.
2. Chemical change: A change where new substances are formed, and it can't be reversed easily is called chemical change.
3. Among the given options, Digestion of food, Baking of a cake and Fermentation of grapes involves the changes where new substances are forming and also it can't be reversed. Therefore, they undergo chemical reaction.
4. Since, tearing of paper doesn't involve a change where any new substance is forming, so it is a physical change and not a chemical reaction.

Explanation for the incorrect options:

1. Option (A) is incorrect because in the digestion of food, enzymatic breakdown takes place which converts food into energy. Our saliva, pancreas, stomach, and intestine contain enzymes that break down lipids, proteins, and carbs in our bodies to produce energy, which is then used for cell development and repair. This process is a chemical reaction because it can't be reversed.
2. Option (B) is incorrect because baking of a cake is a chemical reaction, When cake batter heats up, sugar breaks down into glucose and fructose giving the cake its color which is light brown. This process give rise to a new substance and it is irreversible in nature.
3. Option (D) is incorrect because fermentation of grapes is a chemical reaction as the yeast which are responsible for the fermentation breaks down the sugar in the grapes and form alcohol, which a irreversible change. And also a new substance is formed.

Hence, option (C) is correct. i.e., tearing of paper is not a chemical reaction.