Final answer:
The relationship between the two different samples that decompose when heated, with only one of them being soluble in water, is that they are two different compounds.
Step-by-step explanation:
When heating two different samples, if only one of them is soluble in water, it indicates a difference in their chemical composition. This means that the samples are not the same element or compound and therefore, option d. Both the same compound, is incorrect.
Since elements contain only one type of atom and compounds contain two or more types of atoms, we can eliminate options a. Both the same element and c. Two different elements. Therefore, the correct answer is b. Two different compounds.
For example, if we have Sample A and Sample B and only Sample A is soluble in water, it suggests that Sample A is a compound that dissolves in water while Sample B is another compound that does not dissolve in water.