Question

While teaching the topic of physical and chemical changes, Mahima's teacher listed the conditions that take place during a change.
A) Change in state
B)Change in colour
C) Evolution of a gas
D)Change in temperature
He then asked Mahima to identify the conditions based on which it can be said with certainty that a particular change is chemical in nature. Among the changes that are listed by the teacher, which changes should be selected by Mahima?

Answer 1

Hint :The atoms are rearranged during chemical reactions, and the reaction is followed by an energy shift as new products are produced. The reaction of sodium with water to create sodium hydroxide and hydrogen is an example of a chemical transition. Since there is so much energy emitted, the hydrogen gas released spontaneously burns in the atmosphere. Since the final products are chemically different from the compounds before the chemical reaction, this is an example of a chemical change.

Complete Step By Step Answer:
Physical change
Physical changes affect a chemical substance's appearance but not its chemical composition. Physical changes may be used to isolate mixtures into their constituent compounds, but not to separate compounds into chemical elements or simpler compounds.
Physical changes arise when an entity or material undergoes a change that does not alter its chemical composition. This is in contrast to chemical transition, which occurs when a substance's composition changes or when one or more substances merge or break apart to create new substances. In most cases, a physical change may be reversed by physical means.
Chemical change
Chemical changes occur when a substance mixes with another to create a new substance, a process known as chemical synthesis, or when a substance decomposes into two or more distinct substances, a process known as chemical decomposition. These processes are known as chemical reactions, and they are generally irreversible unless they are followed by more chemical reactions. Some reactions generate heat and are referred to as exothermic reactions, while others require heat to take place and are referred to as endothermic reactions. Chemical changes are an essential aspect of the study of chemistry.
The atoms are rearranged during chemical reactions, and the reaction is followed by an energy shift as new products are produced. The reaction of sodium with water to create sodium hydroxide and hydrogen is an example of a chemical transition. Since there is so much energy emitted, the hydrogen gas released spontaneously burns in the atmosphere. Since the final products are chemically different from the compounds before the chemical reaction, this is an example of a chemical change.
A chemical change is described as any change that is followed by the evolution of gas. As a result, if a gas is produced in a process, it is certain that a chemical change has occurred.
Both physical and chemical changes may cause a change in state. Changes in colour, for example, can occur in both types of changes. For example, when iron is heated, its colour changes to red, and when an iron rod is dipped in a blue copper sulphate solution, the solution turns green due to the formation of iron (II) sulphate.
Similarly, temperature changes can occur as a result of both physical and chemical changes.
So, B is the right answer.

Note :
Both physical and chemical changes may cause a change in state. Changes in colour, for example, can occur in both types of changes. For example, when iron is heated, its colour changes to red, and when an iron rod is dipped in a blue copper sulphate solution, the solution turns green due to the formation of iron (II) sulphate.