pure substance X is solid at room temperature. If the substance is heated to 230 derajat celcius is melted gradually. if then cooled to room temperature , the liquid can not be frozen.
is it possible X of an element or a compound . Explain it
Does it a chemical change occured ? If so can it be said to undergo an endhotherm changing, based on the information provided.
can it be said that the liquid is an element , based on the information provided
Aswer:
Single chemical compound is a substance formed from multiple elements through chemical reactions and compounds also can be decomposed again into its constituent elements by chemical reactions. For example, dihydrogen monoxide (water, H2O) is a compound consisting of two hydrogen atoms for every oxygen atom.

Generally, this fixed ratio must be fixed because of the nature of physics, not the ratio of the chosen people. Therefore, materials such as brass, YBCO superconductors, semiconductors "aluminum gallium arsenide", or chocolate is considered as a mixture or alloy, not a compound.

The characteristics that distinguish compounds is that he has the chemical formula. The chemical formula gives the ratio of atoms in solids, and the number of atoms in a single molecule (hence the chemical formula C2H4 and ethene is not a CH2. The formula does not mention whether the compound is made ​​up of molecules; for example, sodium chloride (table salt, NaCl is an ionic compound .

Compounds can exist in several phases. Most compounds can be solids. Molecular compounds can also be a liquid or gas. All compounds will break down into smaller compounds or individual atoms if heated to a certain temperature (called the decomposition temperature).

Any chemical compound that has been described in the literature have a unique identification number, ie CAS number.