A laboratory simulation of the atmospheric conditions on early Earth uses a gas mixture containing methane (CH4CH_4CH4) and propene (C3H6C_3H_6C3H6).
Explain how methane, a greenhouse gas, acts to keep the simulated planetary surface warmer than it would be without an atmosphere. You should refer to radiation and wavelengths in your answer.
Explain how a researcher could chemically confirm that propene is an unsaturated hydrocarbon. State the reagent used and the observation that would confirm this.