Questions

Milk is not a pure substance since it has so many constituents that can be separated physically.

Compounds are pure substances formed from elements unlike mixtures.

Air Pressure can be defined as the pressure of air in the earth's atmosphere. It reaches a maximum of about 100,000 Pa near sea level and decreases as altitude increases.

The barometer is an instrument which is used for measuring Air pressure.

Physics instruments and their uses:

Barkometer  - - - Tanning liquors used in tanning leather

Bolometer  - - - Electromagnetic radiation

Spectrometer - - -  Properties of light.

Dull means not sharp, not shining, not bright, ...

Hence, the given words are all that means the opposite of dull.

This orbital velocity at the moon is less because orbital velocity = rg

where 'r ' is the orbital radius. i.e the distance of the body from the center of the earth and 'g' is the acceleration due to gravity on the body in question. In the case of the moon, both r and g are less than in the case of the earth.