Heating water in a sealed bottle

In summary, pressure in a bottle of water is related to the temperature and the amount of air in the headspace. The pressure is the same regardless of the volume of the water.
  • #1
redargon
368
0
Say I want to put a bottle of water in the microwave and heat it up. How do I determine the pressure in the bottle as a relation to the temperature of the water? Assuming that there is a headspace of air between the liquid and the bottle cap. Is it dependant on the volume of the air space? ie. would a half filled bottle experince a greater pressure at the same temperature than a bottle that is 90% filled?

I'm trying to use partial pressures, but I'm battling to find out how much of the water is turned into vapour at certain temperatures.
 
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  • #2
As long as the headspace is large enough,
as long as the amount of water is large enough,
the amount of headpace will not influence the pressure​
otherwise
all the water could be varporised​
otherwise
the the dilatation of water could make the pressure increase much faster with temperature​
end
 
Last edited:
  • #3
lalbatros said:
As long as the headspace is large enough,
as long as the amount of water is large enough,
the amount of headpace will not influence the pressure​
otherwise
all the water could be varporised​
otherwise
the the dilatation of water could make the pressure increase much faster with temperature​
end

ummm... I said a bottle of water in a microwave. Think, standard sealed bottle of water. The rest of your post wasn't helpful, but thanks anyway.
 
  • #4
Boiling steam at atmospheric pressure has a partial pressure equal to atmospheric pressure. Use the ideal gas law to calculate the pressure of the air and add the two together. lalbatros is right that the volume of air is irrelevant...unless you intend to heat it past boiling, which I wouldn't recommend. But you can find the associated pressure with a steam table: http://www.efunda.com/materials/water/steamtable_sat.cfm
 
  • #5
So I found out that the vapour pressure of water is about 0.198bar at 60°C (using steam tables as suggested). Now what density do I use for the ideal gas law for calculating the pressure of the air? 1.28kg/m³ (STP) or the value for air at 60°C or the density of the air/water avpour mixture. I'm running myself in circles here because I can't frikkin remember my basic chem... :(
 
  • #6
Also, if I'm using ideal gas laws, couldn't I just use P1/T1=P2/T2. As in, the pressure of gas in the volume of the sealed bottle is atmospheric at 21°C, I stick it in the microwave and the temperature rises to 60°C, so the pressure rises accordingly.
 
  • #7
d'oh. if the volume and the mass stay the same (as they are in the closed bottle), then the density must be constant. Sorry, I think I had a brain fart there.
 
  • #8
Id say that the headspace air does quite a lot.

Consider two cases

One where there is very little air in the bottle. Heating it in the microwave will dilate the water the bottle and the air. Assuming the bottle dilates less then water then pressure will go up and it will compress the air some, plus the dilation of the air.

And one where the there is very little water. So dilation of the water adds very little to bottle pressure but the heating of the air ( by contact to the water or anyway) will be the sole significant contributor.

I'm sure that 1 cm3 of extra air in the headspace doesn't do much but it will be different.

quote from Goldmember: Fat Bastard: "Let's all take o whiff o that" :))
 

1. What happens when you heat water in a sealed bottle?

When water is heated in a sealed bottle, the molecules of water begin to move faster and collide with each other more frequently. This causes the water to expand and create pressure inside the bottle.

2. Is it safe to heat water in a sealed bottle?

Heating water in a sealed bottle can be dangerous as the pressure inside the bottle can build up and cause the bottle to burst. It is important to use caution and follow proper safety precautions when heating water in a sealed bottle.

3. Why does the bottle sometimes expand when heating water?

The bottle expands when heating water due to the increase in pressure caused by the expanding water molecules. The bottle's material may also play a role in how much it expands.

4. Can heating water in a sealed bottle cause an explosion?

Yes, heating water in a sealed bottle can potentially cause an explosion if the pressure inside the bottle becomes too great. It is important to use caution and avoid heating the bottle for too long or with high heat.

5. How long should I heat water in a sealed bottle for?

The amount of time needed to heat water in a sealed bottle will vary depending on the heat source and the size of the bottle. It is important to monitor the bottle closely and stop heating once the desired temperature is reached to avoid potential hazards.

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