The mass of a fixed quantity of gas

Question

1. Increases when the volume increases at constant temperature

 

2. Decreases when the absolute temperature decreases at constant pressure

 

3. Increases when the volume is decreased and the temperature is decreased

 

4. Increases when the pressure is raised and the temperature is constant 

 

5. Does not change at any temperature and pressure

 

Which number is correct?

Answer 1

5

Why woul mass change in the absence of any chemical reaction?