Engine cylinder has an area of 0.01 m2. The gas exerts a constant pressure of 7.5 * 105 Pa on the piston and moves the piston to a distance of 0.04 m. Is work done on the gas or by the gas?

The positive sign indicates that work is done by the gas.

Explanation:

Let consider that gas inside the cylinder behaves ideally and process is isothermal, so that change in internal energy can be neglected. The engine cylinder is modelled after the First Law of Thermodynamics:

The positive sign indicates that work is done by the gas.

they are non-matter

explanation:

they are non-matter. basically, any type of energy or any abstract concept is an example of something that does not matter. other examples include dreams, magnetism, radio, and hate