What takes up more space, one cup of water or one cup of water that has evaporated into water vapor? Why?

Answer 1

The evaporated water takes up WAY WAY more space than the liquid water.

In chemistry we usually use metric measurements for this kind of calculation. So, 18 grams of water will take up about 22.4 liters of space when it is totally evaporated. (one of the other answers shows the exact calculations for this)

You probably know how big a liter is from the size of a coke bottle, right? So line up 22 or 23 of them. Thats how much water vapor you get if you evaporate 18g of water. A cup would hold about 250 grams of water. So, 18 grams is not even 1/10 of a cup.

This is a tremendous increase in volume from liquid to vapor. It happens because in the liquid form the molecules of water are very close to each other, packed very tightly and moving rather slowly. In the water vapor the molecules are split up, each one is travelling very fast speeding around.They bump into each other but they are spread quite far apart compared to their size.... In order to get them going so fast, you have to add a LOT of energy.... that's why it takes a lot of heat to boil a pan of water, or why water outdoors needs a lot of sun and wind to dry it up.

You have a good curiosity, so you will probably study about this when you take chemistry in high school. The main part of this idea is called Boyle's law and was discovered by Robert Boyle, a very smart but wacky English scientist in the 1600s.

Answer 2

Water vapor takes up more space. Gas in general takes up more space then liquid. Gas by definition is more highly excited then liquid and therefore the molecules are bouncing off each other at a higher rate. If you condense water vapor to the size it would occupy if it were liquid it will become liquid. If you rapidly expand it on the other hand it would be come cold, freeze in midair and fall to the ground. Liquid defies normal molecules in one area. When it becomes a solid it's supposed to get smaller but it gets bigger. Ice is larger then water of the same mass. Study boyles law if you want to know more which explains the relationship between pressure, volume, and temperature.

Answer 3

Vapor will take up more space, as the close contact between molecules is broken. Water's density as a liquid is right around 1 g/ml. As a gas, you can figure out its density from the Ideal Gas Law:

PV = gRT/MM
Density = g/V = P * MM /RT

If we use normal conditions (1 atm and 25 C), the density of water vapor is:

Density = 1 atm * 18.0 g/mol / (0.08206 * 298 K) = 0.736 g/L

So 1 gram of water takes up 1.35 L as the vapor, but only 1 ml as the liquid.

Answer 4

One cup of water is confined to the cup it is in. One cup of evapoated water to water vapor takes more space because it is now vapor that is in the air. It isn't just confined to the cup anymore. (Humidity in the summer for ex. it is everywhere)

Answer 5

Water vapor, because the water molecules are further apart.

Answer 6

water vapor... it is because of the nature of the molecules. The molecules of water are a lot closer to each other compared to those of water vapor.

Brush up on basic science. :-)

Answer 7

Wouldnt the water vapour take up the volume of the cup because its become a gas?

Answer 8

Vapor

Density = mass / volume

if the mass is fixed then higher density means lower volume

if you see the densities of water and water vapor, you can see the density of vapor is lower, means it'll have higher volume.

http://en.wikipedia.org/wiki/Density#Density_of_water

Answer 9

one cup of water, takes up more space. the one that evaporated had a physical change and took space in different dimension, i can't say it took up more space.