Solve this:
Short answer type questions
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 change?
Ans 1)When the grapes are attached to the plants, they are still considered as living. They have their immune system intact, due to which they cannot undergo fermentation. After the grapes are plucked, microbes are made to attack them, in the absence of air, to form alcohol. This process is called fermentation and it is a chemical process.
Ans2)(a) This is a Physical change.
Petrol just changes its state from the liquid form to the gaseous form because of the presence of energy in the form of heat. A change of state is a reversible reaction and hence, this is a Physical change.
(b) This is a Chemical change.
Burning of Liquefied Petroleum Gas releases energy and heat as its by products which cannot be converted back to the original reactant. The chemical composition of LPG has changed. Hence, it is a chemical reaction.
(c) This is a Physical change.
The temperature affects the metal temporarily. On reversing the temperature change, the metal goes back to its previous state. Hence, it is a physical state.
(d) This is a Chemical change.
The process of curdling of milk takes place due to bacteria. It is an irreversible reaction in which the composition of milk is changed and hence, a chemical change.
(e) This is a Physical change.
Energy in the form of heat has prompted solid ammonium chloride to evaporate. On reversing the temperature, it goes back to its previous solid state. Hence, this is a physical change.
Hope my answer are right
Ans2)(a) This is a Physical change.
Petrol just changes its state from the liquid form to the gaseous form because of the presence of energy in the form of heat. A change of state is a reversible reaction and hence, this is a Physical change.
(b) This is a Chemical change.
Burning of Liquefied Petroleum Gas releases energy and heat as its by products which cannot be converted back to the original reactant. The chemical composition of LPG has changed. Hence, it is a chemical reaction.
(c) This is a Physical change.
The temperature affects the metal temporarily. On reversing the temperature change, the metal goes back to its previous state. Hence, it is a physical state.
(d) This is a Chemical change.
The process of curdling of milk takes place due to bacteria. It is an irreversible reaction in which the composition of milk is changed and hence, a chemical change.
(e) This is a Physical change.
Energy in the form of heat has prompted solid ammonium chloride to evaporate. On reversing the temperature, it goes back to its previous solid state. Hence, this is a physical change.
Hope my answer are right