Why do scientists measure and record mass instead of weight

Mass is easier to get than the weight. weight is something that can change on the spot.

The mass of our body remains constant everywhere...let it be on moon, sun or jupiter whereas weight changes everytime the gravitational force of a place changes. For example: if we are on moon, our mass is the same as in earth but our weight is 1/6 of the one on earth. To find our weight, knowing our mass is essential. So, mass is easier to find than weight. We must know that mass and weight are complete different things.

Bar graph

Yes it would be a physical change.