What is an isomer?

No. CaCl2 is neither ans isomer, nor does it have isomers.

Ethanol has no structural isomer because of its short chain

C2H6 and isomer would have the same simple chemical formula. In the case of this molecule though, an isomer is not possible.

Because , Cis isomer are same group on same side of the c=c bond . & those are bulky group on the same side , they are formed steric repulsion to each other then Cis isomer are less stable than trans isomer is same group of opposite side of c=c bond no formation of steric repulsion to each other. and trans isomer is more stable than Cis isomer.....

Yes it is. It's structural isomer is ethanol C2H5OH

Yes. Ethanol is a structural isomer of dimethyl ether. CH3OCH3.

An isomer shares the same number of the same atoms, but they are configured differently.

If you mean what is an isomer then it is a compound with the same chemical formula but with a different structure

No, it is NOT either both. Besides 'benzenepropanol' is not an official name.

Isomer is the term used for chemical compounds having the same molecular formula, in physics the term isomer is meaningless although the term Isotope is used.

Z isomer are cis isomer it has the tow groups at the same side around the double bond but the E isomer are trance isomer it has the tow groups at opposite side around the double bond.

methoxy methane is a functional group isomer of ethanol. CH3-O-CH3

yes, it is functional isomer of diethyl ether and methylpropyl ether.

Ammonia (NH3) hasn't an isomer. The solution of ammonia in water is called ammonium hydroxide.

I'm guessing it's because butane is an alkane, which means it only consists of single bonds, so you can't form a geometric isomer because it will be the isomer no matter how you change it.