Thermal and elctrical conductivity of a solid is same in different directions.
Name the phenomenon involved

Write two different vectors having same direction.

Assertion : In crystalline solids, the value of resistance is different in different directions. Reason : Crystalline solids are isotropic in nature.

Refractive index of a solid is observed to have the same value along all directions. Comment on the nature of this solid. Would it show cleavage property?

There are two compounds of sodium whose formulae are different by one H atom. Both the compounds can be prepared by the same process. One compound can be used for washing purpose and other can be used in fire extinguishes. Name the method of preparation.