FAQs on L3 : Chemical Change - Physical & Chemical Changes, Science, Class 7

Question 1

1. What is a chemical change?

Accepted Answer

Ans. A chemical change, also known as a chemical reaction, is a process in which one or more substances are transformed into different substances with new properties. It involves the breaking and formation of chemical bonds, resulting in a new arrangement of atoms.

Question 2

2. What is the difference between a physical change and a chemical change?

Accepted Answer

Ans. A physical change involves a change in the physical properties of a substance, such as shape, size, or phase, without any change in its chemical composition. On the other hand, a chemical change involves the formation of new substances with different chemical properties.

Question 3

3. How can we identify if a change is a chemical change?

Accepted Answer

Ans. There are several indicators of a chemical change. Some common signs include the evolution of gas, formation of a precipitate, change in color or odor, release or absorption of heat, and production of light or sound. These observations suggest that a chemical reaction has taken place.

Question 4

4. What are some examples of chemical changes?

Accepted Answer

Ans. Examples of chemical changes include burning of wood, rusting of iron, cooking food, digestion of food in our body, and souring of milk. In each of these cases, new substances are formed with different chemical properties.

Question 5

5. Can a physical change be reversed, unlike a chemical change?

Accepted Answer

Ans. Yes, a physical change can often be reversed by applying appropriate physical conditions. For example, melting ice can be reversed by cooling it, and boiling water can be reversed by condensing the steam. In contrast, a chemical change is usually irreversible, as it involves the formation of new substances.

L3 Chemical Change - Physical & Chemical Changes, Science, Class 7 Video

Physical Sciences for Grade 10

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