Question

The gas in the piston is being heated, and the piston has moved upward. The observation will be summarized in a row of the incomplete table below.
A container with a piston inside it. An arrow above the piston points upward.

Row
Name
Observation
Variables
1
Boyle's law
Volume increases when
pressure decreases
?
2
Charles’s law
?
?
3
Gay-Lussac’s law
?
Temperature, pressure
4
Combined gas law
?
?

What are the variables for this piston?
temperature only
temperature and volume
pressure and number of molecules
volume and number of molecules

Answer 1

Temperature and volume.

Heating the gas raises its temperature and the piston moves up so the gas volume increases. The pressure stays essentially constant (piston free to move), so the changing variables are temperature and volume.