In the scenario you described, where a heavy piece of concrete is lifted and placed on a case filled with gas, and the case is slowly compressed due to the weight of the concrete, the gas inside the case would experience an increase in temperature. This increase in temperature is a result of the compression work done on the gas.
When the gas is compressed, its volume decreases, and as a result, the gas molecules collide more frequently with each other and the walls of the container. These collisions result in an increase in the kinetic energy of the gas molecules, which corresponds to an increase in temperature.
However, it's important to note that the energy required to lift the piece of concrete initially is not directly converted into heat energy inside the case. The work done to lift the concrete is stored as potential energy in the gravitational field, not as heat energy. When the concrete is lowered onto the case, the potential energy is transferred to the concrete-case system, and part of that energy is converted into heat due to the compression of the gas.
In an ideal scenario where there are no energy losses due to factors such as friction or inefficiencies, the energy used to lift the concrete should be equal to the increase in energy of the gas due to compression. However, in real-world scenarios, there are typically energy losses, so the energy obtained from the compressed gas may be less than the initial energy used to lift the concrete. Energy losses can occur due to factors like heat dissipation, mechanical inefficiencies, or other losses in the system.
It's important to consider the conservation of energy in any system, but it's unlikely that compressing the gas in the case through the described process would result in obtaining more energy than was initially used to lift the concrete.