Is dissolving a solid a physical or chemical change

Dissolving a solid in liquid is a physical change . For eg table salt in water is a physical change because only the state of the matter has changed. Allowing the water to evaporate will return the salt to a solid state. Thus, dissolving a solid is a physical change.

the answer is c.the valence of the atoms combine .

on passing the small ampere of electric current through the tube made of ar and hg of cfl generates uv rays which excites the fluorescent and thus emits the high radiation by consumption of just 5- 12 w in comparison to incandescent light which requires more power such as around 40 - 55 w to lighten.

moreover the life span of fluorescent or cfl is around 8000 h whereas the life span of incandescent is around 1200 h

hence, the building installed with incandescent lights bears more electricity bill.