A. Phase changing. When phase changes nothing chemically changes about the substance, its still the same thing.
A double bond in chemistry is a chemical bond between two chemical elements involving four bonding electrons<span> instead of the usual two. The most common double bond, that is between two </span>carbon atoms<span>, can be found in </span>alkenes<span>. Many types of double bonds exist between two different elements.</span>
Answer:
C) is correct answer . <em /><em />