Lipids is the answer to this question. The main reason why you can tell that this is lipids is because of the reaction of water with the other liquid. They separated from each other. Lipids are unable to mix with water properly. If in case you are not too familiar with what lipids are, you can find them in various forms.
They can be in the form of fat, wax, or even oil. Lipids are known to contain different elements like hydrogen, oxygen, and carbon. Take note that lipids can help improve the function of living cells. Can you imagine if you do not have any living cells?