This unit explores a recent and controversial theory of the origin of much of the Earth's natural gas and oil. The materials provided will give students the opportunity to: (1) gain an understanding of science and what is involved in the acceptance or rejection of theories; (2) learn about fossil fuels, especially natural gas; (3) learn the traditional and abiogenic theories of natural gas formation; (4) evaluate the merits of the two theories; and (5) evaluate the knowledge gained about natural gas and its origin. Included in the unit are an introduction, with objectives; an outline and notes to the teacher; an activity on the controversy of science; a fossil fuel and natural gas fact sheet and activities; an article on theories and questions for discussion and review; a viewing guide and discussion questions to use with a related videotape; a critical thinking activity for debate or role play; a quiz; and an evaluative worksheet. An appendix on the supply of natural gas, a list of additional available materials, and a glossary complete the unit. (RT)