The statement “force equals mass times acceleration” is newton’s second law of motion. why is this a law rather than a theory?

It will always be true.  It applies to everything and it is literally proven to be true.  

Well, both latitude and intensity of light affect temperature because, the higher the light intensity, the higher the temperature and since latitude is the measure of how close you are to the equator, then the closer to the equator you are, the higher the temperature is.