NCERT Question 2 - Chapter 6 Class 7 - Physical and Chemical Changes

State whether the following statements are true or false. In case a statement is false, write the corrected statement in your notebook.

1. Cutting a log of wood into pieces is a chemical change. (True/False)
2. Formation of manure from leaves is a physical change. (True/False)
3. Iron pipes coated with zinc do not get rusted easily. (True/False)
4. Iron and rust are the same substances. (True/False)
5. Condensation of steam is not a chemical change. (True/False)

Answer:

(a) Cutting a log of wood into pieces is a physical change as it results in the formation of no new substances , and no changes in the chemical properties of wood.

• Hence, the statement is false.

(b) Formation of manure from leaves is a chemical change. It is irreversible , and a new substance (manure) is formed.

• Hence, the statement is false .

(c)   Iron pipes coated with zinc do not get rusted easily. The process is called Galvanisation . It is used to prevent iron pipes from rusting .

• Hence, the statement is true .

(d) Iron reacts with water and oxygen to form Iron Oxide . This Iron Oxide (reddish brown in colour is known as Rust . 

• Hence, the statement is false .

(e) Condensation of steam is a physical change as water only changes its state , and the process is reversible .

• Hence, the statement is true .