posted by Ashleigh on .
Compressing gases requires work and the resulting energy is usually converted to heat; if this heat does not escape, the gas's temperature will rise. This effect is used in diesel engines: The compressed air gets so hot that when the fuel is injected, it ignites without any spark plugs.
As an example, consider a cylinder in a diesel engine in which air is compressed to one twentieth of its original volume while the pressure rises from 1 atm to 40 atm (absolute not gauge). Note that because the air heats up while being compressed, its pressure rises more than twenty-fold.
If the air is taken into the cylinder at 11 degrees Celsius, how hot does it get after being compressed? Answer in degrees Celsius