Chemistry-
General
Easy
Question
Which of the following is a chemical change?
- Baking of cake
- Evaporation of salt solution
- Heating of a piece of a paper
- Both (A) and (C).
Hint:
- In a physical change the appearance or form of the matter changes but the kind of matter in the substance does not. However in a chemical change, the kind of matter changes and at least one new substance with new properties is formed.
The correct answer is: Baking of cake
- When a substance undergoes a physical change, its composition remains the same despite its molecules being rearranged. When a substance undergoes a chemical change, its molecular composition is changed entirely. Thus, chemical changes involve the formation of new substances.
-
The process of obtaining salt by the evaporation of sea water is a process of crystallization which is a reversible process and a physical change, these crystals will convert again in salt solution (seawater) by dissolving them in water.
- Burning of paper is a chemical change because as a result of burning, ash is formed as a new chemical substance. During burning, Carbon react with hydrogen and oxygen, turning them into Carbon dioxide ( ) and water. These changes are irreversible and ash can not be converted back to the original substance.
- For baking a cake, we first make the batter and then put it in the oven. Heat is provided inside the oven and then this batter changes into a cake. Once the cake is formed, we cannot get back the original batter and the chemical composition of cake is different from that of batter. In any physical change, the chemical composition of a substance does not change. Hence baking of cake is not a physical change but a chemical change.
The process of obtaining salt by the evaporation of sea water is a process of crystallization which is a reversible process and a physical change, these crystals will convert again in salt solution (seawater) by dissolving them in water.
- Burning of paper is a chemical change because as a result of burning, ash is formed as a new chemical substance. During burning, Carbon react with hydrogen and oxygen, turning them into Carbon dioxide ( ) and water. These changes are irreversible and ash can not be converted back to the original substance.
- For baking a cake, we first make the batter and then put it in the oven. Heat is provided inside the oven and then this batter changes into a cake. Once the cake is formed, we cannot get back the original batter and the chemical composition of cake is different from that of batter. In any physical change, the chemical composition of a substance does not change. Hence baking of cake is not a physical change but a chemical change.
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