Table A: Calculation of Density for Regularly Shaped Solids Table
tennis
ball
Golf
ball
Mass
(g)
Diameter
(cm)
Radius
(cm)
Estimated volume
(cm3
)
Estimated density
(g/cm3
)
Prediction of buoyancy
Circle one.
Float Sink Float Sink
Observation of buoyancy
Circle one.
Float Sink Float Sink
Initial volume of water
(cm3
)
Final volume of water
(cm3
)
Change in volume
(cm3
)
Calculated density
(g/cm3
)
Error
(%)
Table B: Calculation of Density for Irregularly Shaped Solids

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. 

☆ionisation energy increases across a period from na -> ar☆ionisation energy decreases down a group from li -> fr☆ionic radius decreases across a period from na -> cl☆ionic radius increases down a groupfrom f -> ii hope it clarifies your doubts

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

Answerhund's rule;