Question

Grapes hanging on the plant do not ferment but after being plucked from the plant can be fermented. Under what conditions do these grapes ferment? Is it a chemical or a physical?

Answer 1

Hint: Physical changes are those in which the physical properties of the substances change whereas chemical changes are those in which the chemical properties of the substances change. Chemical changes are not reversible whereas physical changes are reversible.

Complete answer:
Grapes which are hanging on the plants still have life so they do not ferment and hence as they are alive, their immune system is still working. But we plucked from the plant, they are now not alive; they are dead hence their immune system also stops working and hence they ferment.
The condition under which microorganisms like yeast ferments grapes and wine are known as anaerobic. This condition occurs in the fermentation vessel, once the oxygen is removed and replaced with $N_2$, $C{O}_2$, or another by-product of the fermentation process. It is usually a slower process. In this process, Anaerobes grow under the affirmative conditions used to less contamination during fermentations because they have unusual enzymes and catabolic pathways. As less amount of biomass is produced in anaerobic fermentations, thus more carbon can be converted as an end product and a higher amount of product is formed. Thus it is an irreversible process. So it is the chemical change.

Note:
Remember that physical changes are temporary change and reversible while chemical changes are permanent change and not reversible. In physical change, there is no formation of new products whereas in chemical change, there is formation of new products.