Lavoisier would have taken mercury and heated it up to 350 degrees centigrade in air and then found that a new compound was formed a red or yellow mineral which would be mercury oxide so the experimental observation would be the change in color of the mercury and the formation of a mineral with different properties from pure mercury.
The independent variable should be the plants you used.
The greenhouse is the cause of most climate warming and glacier retreat in the past 50 years, however, related causes like farming, burning fossil e.t.c are also causing glacier retreat
