Final answer:
You have likely discovered unrefined petroleum (crude oil), given its detailed properties and composition. This material can be refined into various products like gasoline and petrochemicals, and its identity is supported by analytical techniques such as combustion analysis.
Step-by-step explanation:
If you discover a material under Earth with the properties of being liquid, flammable, having a low combustion rate, the ability to ignite at low temperatures, a strong odor, dark brown or black color, thick, sticky, and semi-fluid in nature, with a composition including compounds with a long chain of carbon and hydrogen atoms bonded together, you're likely describing a form of unrefined petroleum or crude oil. These properties are characteristic of hydrocarbons, which are the main components of petroleum.
Many of these properties, such as flammability and the presence of long chains of carbon and hydrogen atoms, suggest the material could be processed into various petroleum products, such as gasoline, diesel, and other petrochemicals. The description matches well with the known properties of crude oil, which is the raw material used in the production of many energy and chemical products.
The evidence supporting this claim includes the composition analysis, such as those detailed in combustion analysis, where hydrocarbons yield carbon dioxide and water upon complete combustion. These procedures help identify the elemental makeup and ratios in compounds, further confirming the substance as a hydrocarbon.