Why are tropical air masses warmer than cold air masses? What region is responsible for warm, humid weather at times during the summer in the Central Plains states?

What region is responsible for cool, humid weather at times during winter for eastern states?

What region is responsible for hot, dry weather during the summer in the desert southwest?

Mass is the amount of matter in an object.  weight is the measurement of the pull of gravity on an object.  say for example, you travel to the moon which has a different gravitational field compared to the gravitational field of earth. (gravitational fields: earth = 1, moon = 0.165)  now when you are on the moon, the pull of gravity on you is different than on the earth. and as weight is the measurement of the pull of gravity on an object, that means yes, your weight can and will change on the moon.  however, on the moon, on earth or even on jupiter, the amount of mass inside of you remains the same. meaning your physical mass remains constant.  in conclusion it is possible for your weight to change as your mass remains constant. 

Iron reacts with oxygen in a chemical hand-warmer. how should this reaction be categorized? the correct answer is: a). as an exothermic process because it releases heat