You walk in the front door of your house. you smell an onion that someone is cutting in the kitchen. explain why you are able to smell it, what this process is called, and what other types of substances exhibit this behavior.

Plants let out volatile organic compounds as a chemical defense and first aid. this can be found when the plant is being injured; like cutting grass and chopping an onion.

Wind will blow from one direction to another.

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.