Matter in Our Surroundings — Science STD 9 — Question

What is a mixture? Give two example of mixtures.

Calculate the molecular masses of H₂ , O₂ , Cl₂ , CO₂ , CH₄ , C₂H₆ , C₂H₄ , NH₃ , CH₃OH.

Define ‘formula unit’ of an ionic compound. What is the formula unit of:

1. Sodium chloride
2. Magnesium chloride?

You have been given a suspension and a solution. How could you tell the difference between them by their appearance?

Classify the following into solution, suspensions and colloids:
Soda-water, Milk, Brine, Blood, Ink, Smoke in air, Chalk water mixture, Milk of Magnesia, Shaving cream, Muddy river water.

Define dispersion medium.

Name two solid, two liquids and two gaseous elements at the room temperature.

What is the significance of the formula of a substance?

A student placed a gas jar containing air in the upside down position over a gas jar full of red-brown bromine vapours. He observed that the red brown colour spread upwards into the jar containing air. Based on this observation, the student concluded that it is only the bromine vapour which moves up and diffuses into air in the upper jar, the air from the upper jar does not move down by diffusion into the lower jar containing bromine vapours. Do you agree with this conclusion of the student? Give reason for your answer.

What is meant by ‘diffusion’? Give one example of diffusion in gases.