Answer: Water is the only known substance on Earth that exists naturally in three states: solid, liquid, and gas.
Explanation:
<span>A substance that can be separated into two or more substances only by a chemical change is </span><span>known as a </span><span>heterogeneous</span><span> mixture</span>
Cu2S is the one that is going to form a precipitate and Cu(NO3)2 will not form a precipitate because it is soluble. It is a fact that those that are insoluble will form a precipitate. I hope that this is the answer that you were looking for and the answer has actually come to your desired help.
D. A set of steps that help scientists gather knowledge