What always forms when a chemical reaction occurs?

A physical change always forms when a chemical reaction occurs - Physical changes are often changes that effect the form of any chemical substance except its chemical composition.

as resources become scarce because of population growth, the growth decreases after few years due to lack of resources and food.

imagine a line passing through the center of earth that goes through both the north pole and the south pole. this imaginary line is called an axis. earth spins around its axis, just as a top spins around its spindle. this spinning movement is called earth's rotation. at the same time that the earth spins on its axis, it also orbits, or revolves around the sun. this movement is called revolution.