Fuel fuel. They are also used to start a coal fire. Liquid fuels are combustible or energy-generating molecules that can be harnessed to create mechanical energy, usually producing kinetic energy; they also must take the shape of their container. It is the fumes of liquid fuels that are flammable instead of the fluid. Most liquid fuels in widespread use are derived from the fossilized remains of dead plants and animals by exposure to heat and pressure inside the Earth's crust. However, there are several types, such as hydrogen fuel (for automotive uses), ethanol, jet fuel and bio-diesel which are all categorized
Interlanguage fossilization 1) why fossilization occurs, 2) the precipitating conditions, 3) what kind of linguistic material is likely to be fossilized, and 4) what type of learners are more prone to fossilize. However, there has been almost no investigation by SLA theorists on the possibilities of preventing or overcoming fossilization, and little explanation related to those adult second language learners who overcome one or more "areas of stability" in interlanguage—those learners whose interlanguage does not fossilize, and who reach a high level of proficiency in the second language. One factor of obvious relevance is motivation, and studies have been conducted regarding motivation