why does 1cm3 of water always have a mass of 1 gram?

Ollie20

any ideas?
thanks
xXx

Reply 1

EierVonSatan

Ollie20

any ideas?
thanks
xXx

because the definition of a gram is 1 mL of water (at room temperature, different volume at different temperatures)

Reply 2

Ollie20

thanks, but do you know why in terms of particles?

Reply 3

Sanjetti

Ollie20

thanks, but do you know why in terms of particles?

What do you mean?

Reply 4

Slumpy

Because water has a density of 1000 kg per cubic metre?

Reply 5

TheLostProphet

Cause at standard conditions the number of particles will be the same [1]. Under standard temp, pressure, etc., the particles will have the same average energy. Therefore the distance between them will also be on average the same.

Not sure if this is exactly 1gram, it might not be, the Kilogram is defined as the mass of a Platinum-Iridium alloy and a gram is 1/1000 of that. If it's not exactly 1g [1.00000000000000 and so on forever], then obviously it's just used for convenience when you do calculations.

Reply 6

charco

Study Forum Helper

The exact density of water is temperature dependent - it is not 1.0000 g cm^-3

Water's maximum density is 0.999973 g cm^-3 which it achieves at 4ºC

Reply 7

Fabregas1989

because that's the definition of a gram!!!!!!!!!!!!!!!!!!!!!!!!!

Reply 8

Chrrye

^LOL

Reply 9

Reue

"Why do 100 centimetres fit exactly into a metre?"

See the similarity?

Reply 10

charco

Study Forum Helper

not quite - water does not have a density of 1.0000 g cm^-3 (see above)

Reply 11

ashy

charco

not quite - water does not have a density of 1.0000 g cm^-3 (see above)

I think it is when assumed at standard temperature and pressure.

Reply 12

charco

Study Forum Helper

ashy

I think it is when assumed at standard temperature and pressure.

At STP the density of water is 0.997

Here is a water density table at different temperatures

Reply 13

fisherman

charco

At STP the density of water is 0.997

Here is a water density table at different temperatures

Yep, charco is right, and the OP's question is wrong, 1cm3 of water does not always weight 1g.

Reply 14

qgujxj39

Well obviously experimental errors were made when creating the definition, so I suppose they've stuck. Getting exactly 1 when the actual answer is 0.999973 isn't too bad, really.

Reply 15

ashy

charco

At STP the density of water is 0.997

Here is a water density table at different temperatures

Fair enough, then :smile:

Reply 16

Clickers

fisherman

Yep, charco is right, and the OP's question is wrong, 1cm3 of water does not always weight 1g.

It depends on the tempeture, air pressure.

Reply 17

Daniel327

I'm not saying you are wrong, but if this is so then why do we rely on a physical entity to define 1kg rather than simply stating that it is the mass of 1000ml of water?

Reply 18

Pigster

Original post by Daniel327

I'm not saying you are wrong, but if this is so then why do we rely on a physical entity to define 1kg rather than simply stating that it is the mass of 1000ml of water?

I'm fairly sure that after more than ten years, you're unlikely to move this conversation on, much. Better to just start a new conversation of your own. Also, welcome to TSR.

Reply 19

Dylann

Original post by Daniel327

I'm not saying you are wrong, but if this is so then why do we rely on a physical entity to define 1kg rather than simply stating that it is the mass of 1000ml of water?