MEDIUM
7th CBSE
IMPORTANT
Earn 100

Write the valency of the following element 

Calcium

Important Questions on Chemicals and Chemical Changes

EASY
7th CBSE
IMPORTANT

Write the valency of the following element

Copper

EASY
7th CBSE
IMPORTANT

Write the valency of the following element

Oxygen

MEDIUM
7th CBSE
IMPORTANT

Balance the following chemical equation:

FeS+O2Fe2O3+SO2

EASY
7th CBSE
IMPORTANT

Balance the following chemical equation:

Na + Cl2  NaCl

MEDIUM
7th CBSE
IMPORTANT

Balance the following chemical equation: 

CO2+CaOH2CaCO3+H2O

EASY
7th CBSE
IMPORTANT
It is Diwali time. Rajat is having school holidays. He wants to help his parents with the work at home. He noticed that the iron grills of the windows have turned reddish-brown and are looking bad. So he asks his father what they could do to make them look good again. What suggestion will you give to Rajat? Why?
MEDIUM
7th CBSE
IMPORTANT
Manisha was at home on account of school holiday. In the evening when her father returned from work, she decided to prepare a cup of tea for him. She poured hot boiling tea in a glass cup and the cup cracked. She was upset but her father consoled her and told her the reason of the cup cracking. What was the reason? What kind of change is it?
EASY
7th CBSE
IMPORTANT
Melting of butter is a physical change.