Why don't chemists use weight as a measure of the quantity of matter presented in a sample?

Answer 1

Weight is not the same thing as mass. Weight is the gravitational force exerted on the object, (or, equivalantly, the force needed to to counteract the gravitational force, like the force of a spring needed to hold the object up). On the surface of the earth, this is basically only dependant on the object's mass (although the earth is not a perfect sphere of uniform density, which means the weight of an object depends on where you are, and the spinning of the earth requires a centripital acceleration which reduces the apparant weight of an object more at the equator than at the poles. Also, the atmosphere can affect weight measurements. This effect is not significant for dense objects, but is responsible for giving helium balloons an apparant negative weight, and reduces the apparant weight of lesss dense objects more strongly than dense ones) However, an objects weight would change enormously depending on whether it is on the earth, the moon, Jupiter, or somewhere else. It is the mass of the object that would remain unchanged in all of these instances. Mass is used as a measure of the quantity of matter present.

Answer 2

Because chemical reactions depend on a sample's mass, not on its weight.

The sample's weight is a pretty good indicator of its mass, but it's not perfect because weight varies from place to place. For example, a gram of salt weighs more at the north pole than it does at the equator (because of the shape & rotation of the earth).

Also, any measurements you make of the sample's weight become meaningless if you take the sample off the earth completely.

Answer 3

Weight varies based on the force of gravity in a certain area, whereas mass is constant everywhere.

Answer 4

because weight can change depending on the surroundings--for example you would weigh a LOT less on the moon than you do on earth, but your mass would stay the same. so they use mass because its always constant no matter where you are.

Answer 5

Because it is irrelevant. Does size matter? It would depend on the products application.

Answer 6

they do how do you think they find grams but thats deceptive because what they are really doing is mole to weight thing not just weight

Answer 7

A lb. of feathers takes up much more room than a lb. of bricks, right?

Answer 8

They do, it's given in grams.