Is Matter Around Us Pure? — Science STD 9 — Question

Calculate the molar mass of the following compound:
Na₂CO₃

What name is given to the sound waves of frequency too low for humans to hear?

Name the law of chemical combination:
Which was given by Proust.

If the weight of a body on the earth is 6 N, what will it be on the moon?

Name the process you would use to separate ammonium chloride from a mixture of sodium chloride and ammonium chloride.

There are three small bones in the middle ear-anvil, hammer and stirrup:
Which of these bones is in touch with oval window?

What is the number of sub-atomic particles in this isotope?

What is the physical state of water at:

1. 250ºC
2. 100ºC

Classify each of the following, as a physical or a chemical change. Give reasons:
Change in the colour of black tea on adding lemon juice to it.