The characteristics of two different types of reactions are shown below: Reaction A: Protons are gained or lost by the atom of an element.
Reaction B: The identity of the reacting element does not change.

Which statement is true about the two reactions?

A. Valence electrons are not involved in both Reaction A and Reaction B.

B. Valence electrons are involved in Reaction B but not in Reaction A.

C. Valence electrons are involved in both Reaction A and Reaction B.

D. Valence electrons are involved in Reaction A but not in Reaction B.

The correct answer is b

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. 

While unproven, it uses facts to support part of a conclusion. it is still factual and has predictive power, however.

Hbr dissociates to form h+ and br-ca(oh)2 dissociates to form ca2+ and 2oh-the h+ and oh- react to form waterassuming the reactants are dissolved in water, the net reaction is h+ + oh- —> h2oif you’re asked to show all components of the reaction, the complete reaction is 2hbr + ca(oh)2 —> cabr2 + 2h2o