[Portomar1970]

I did a project for my chemistry class that involved the absorbency of sanitary napkins and whether more expensive brands absorb better.

Here is how I did the project:

I purchased 4 different sanitary napkin brands and started the experiment by weighing each one's initial weight on a scale. I then put each napkin into a bowl with water (300 ml each bowl). After the duration of one hour, I once again weighed each napkin and recorded it. I subtracted the initial weights of the pads from the weights with the water to reach the conclusion on which pad absorbed better. So my whole project, data tables, charts, procedures and such, I used the word "weight gained" but after thinking about it a little more, should it be mass instead of weight gained?? I already did the whole project and was just about ready to paste everything to the poster board, but now I am not sure.

Thanks
Stella

[mikasaur]

Mass is a measurement of the amount of matter something contains, while weight is the measurement of the pull of gravity on an object. Since you did all of your experiments on the surface of the earth, I think it's okay to use either. Though you'll usually see mass instead of weight for chemistry/physics labs (I think).

I'll let one of the actual scientists weigh in (no pun intended) on which is more appropriate for an experiment like that.

[Burner]

I am not an actual chemist, but to me it depends on the unit of the quantity you measured. If you measured the 'weight' of your napkins in grams/kilograms(a unit of mass), then you should use the term 'mass'. If you measured it as Newton(a unit of weight, commonly used in spring balances, but who will use a spring balance in Chemistry experiments??), then you should use 'weight'.

[magician4]

if you were very picky, you would argue that using "mass" would require to show your result as " kgs " ( or parts thereof), and if you were using "weight" (assuming that the effective gravitational pull at your very place is "normal", i.e. 9,81 kgs m / sec² ), you should show "N" instaed
(note: 1 kg results the weight of 9,81 N [on earth's surface, on average] )

for all practical purposes, nobody does so in chemistry: we all talk "mass" ( and the respective unit thereof), as determined by using ( more or less well-calibrated) scales, i.e. after really measuring "weight"

regards

Ingo

[Corribus]

Weight incorporates the force due to gravity. Your balance is (should be) calibrated for whatever your current elevation is. The units it gives are likely in grams or the equivalent, so the appropriate way to describe the measure is the mass. Weight would have a unit of force.  Although confusingly enough, the accepted verb for measuring mass is weighing something, so go figure.

[Borek]

Your balance is (should be) calibrated for whatever your current elevation is.

If it is a spring or electronic balance.

[sasa4m]

mass refers loosely to the amount of "matter" in an object (though "matter" may be difficult to define)
 weight refers to the force experienced by an object due to gravity.