What is conserved when two objects collide in a closed system

An insulated 40 ft^3 rigid tank contains air at 50 psia and 120°f. a valve connected to the tank is now opened, and air is allowed to escape until the pressure inside drops to 25 psia. the air temperature during this process is kept constant by an electric resistance heater placed in the tank. determine the electrical work done during this process.

Which insurance would contradict the big bang theory

What can change the speed of sound as it travels through the ocean? a. salinity only b. density and salinity c. salinity and distance from land d. density and distance from land