| 2023-05-12 | C2H6 compound |
| 2022-09-17 | Compound that becomes a man's name when its last letter is removed |
| 2021-07-01 | C2H6 |
| 2021-05-15 | Odorless hydrocarbon |
| 2020-09-26 | Flammable compound with two carbons |
| 2019-11-20 | Gas that's a man's name + E |
| 2019-09-29 | Simple hydrocarbon |
| 2019-08-19 | Component of natural gas |
| 2018-10-14 | Natural gas component |
| 2018-06-26 | Gas in fuel |
| 2018-05-27 | Component of natural gas |
| 2017-11-23 | C2H6, familiarly |
| 2015-10-13 | Component of natural gas |
| 2015-09-06 | Byproduct in petroleum refining |
| 2014-11-09 | Byproduct of petroleum refining |
| 2013-12-12 | Gas with or without an "m" |
| 2013-03-29 | Second-simplest hydrocarbon |
| 2012-12-09 | Petroleum component |
| 2012-10-13 | Crude component |
| 2012-04-22 | Natural gas component |
| 2011-09-13 | Gaseous hydrocarbon |
| 2010-10-17 | Flammable fuel |
| 2010-10-16 | Hydrocarbon with two carbons |
| 2010-05-14 | Crude component |
| 2009-01-26 | Flammable gas |
| 2008-06-13 | Cryogenic refrigerant |
| 2007-11-11 | Flammable gas |
| 2007-02-28 | Colorless gas |
| 2006-08-16 | Simple hydrocarbon |
| 2002-12-29 | C2H6 |
| 2002-03-24 | Crude petroleum component |
| 2001-06-26 | Odorless gas |
| 2001-03-18 | Constituent of natural gas |
| 2000-04-28 | Fuel gas |
| 1999-12-27 | Flammable fuel |
| 1999-09-21 | Natural gas ingredient |
| 1998-06-06 | Natural gas component |
| 1998-04-06 | Component of natural gas |
| 1998-02-18 | Fuel gas |
| 1998-01-25 | Natural gas component |
| 1997-03-10 | C2H6 |
| 1997-01-22 | Odorless gas |
| 1994-08-28 | Gas fuel |