Thermal expansion of a gas causes a change in the of the gas. A. Radioactiveness
B. Density
C. Mass
D. Altitude

B. Density

Explanation:

Thermal expansion of a gas will cause a definite change in the density of the gas.

It is product of an increase in the average kinetic energy of the system in which molecules are found.

Therefore, thermal expansion of gas will cause a change in the density of the gas.