a)When silver nitrate comes in contact with skin, it is reduced to white color metallic silver.In most cases, a black stain appears due to formation of finely divided silver which has black color.

The black color is due to the decomposition of the Ag+ ion into Ag, silver. Silver nitrate will slowly decompose with the silver ion reverting to elemental silver. The microscopic particles of silver are so small that they absorb light instead of reflecting it, and so appear black, instead of silver....

It is theoretically possible for a substance to have a negative value of cubical expansivity, which means that the substance would contract rather than expand when the temperature increases. However, it is very rare for a substance to have a negative value of cubical expansivity over a significant range of temperatures.

One example of a substance that has a negative value of cubical expansivity over a limited range of temperatures is water. Water has a positive value of cubical expansivity at...

Matter is anything that possesses mass, occupies space and may be perceived through one or more senses.

                           The physical divisions of matter are:

1. Solid : Solid matter is composed of tightly packed particles. A solid will retain its shape; the particles are not free to move around.

2. Liquid : Liquid matter is made of more loosely packed particles. It will take the shape of its container. Particles can...