Hammer the coal into a coarse powder.
Place your finger in the small end of the funnel and pour the coal into the large end of the funnel, keeping the coal in the funnel with your finger.
Turn the jar upside-down, and place it over the funnel.
While holding the funnel tight against the bottom of the jar, turn the jar upright and place it on a table.
Remove your finger and slowly fill the jar with water until the funnel is completely covered, being careful not to wash the coal out of the funnel.
Then fill the test tube with water and place it upside-down over the small end of the funnel, being careful not to let any air into the test tube.
Mark the water line on the test tube with the rubber band.
Observe the test tube over a two- to three-day period as it fills with methane gas.