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Visual of ETH vs Water

Posted: Mon May 06, 2024 3:02 am
by EricTheRed
https://www.facebook.com/reel/438667965519065

Now you can see the different boiling points! :D

Re: Visual of ETH vs Water

Posted: Wed May 08, 2024 1:31 am
by CeLox
That is some very nonesense "experiment", just some dumb reels or whatever they are called.
We don't know anything from the materials they used and their properties.

Actually, you don't see the boiling point here. What we see is the effect of the specific heat capacity: it is the amount of energy (heat) you need to put into a material to increase the temperature of 1 kg material to 1 °C or 1 °K.

For example: water has the 2nd highest specific heat capacity known on Earth! with 4.18 kJ/kg*K -- and this actually means, you need to put 4.18 kJ worth of energy to 1 kg of water to increase its temperature 1 °C (or 1 °K). H2 (hydrogen) has the highest specific heat capacity with 14.3 kJ/kg*K
On the other hand, ethanol has a value of 2.43 kJ/kg*K.

Assuming it is pure Ethanol in the experiment and pure H2O, the temperature of Ethanol will increase much faster and - for sure - start to evaporate earlier and thus, less amount of Ethanol is available and thus, the temperature will start to increase again faster.

if somebody wants to have a look on thermodynamics, please enjoy yourself: https://en.wikipedia.org/wiki/Specific_heat_capacity

Re: Visual of ETH vs Water

Posted: Wed May 08, 2024 3:56 pm
by zach
The magnitude of the change in sensible heat or specific heat capacity is relatively small compared to the energy required for phase change .

For example it takes 1 Btu to increase 1 lb of water 1 degree F. At atmospheric pressure it takes 970 Btu per pound to vaporize water at 212 F. (100 C)

So the energy to heat 1 lb of water 60 F to 212 F is 152 Btu's. To change that pound from liquid to vapor at 212 F it takes 6 times more energy.

For ethanol, the latent heat of vaporization is 364 Btu/lb. So the boiling rate is nearly 3 times the rate of water with the same heat input.

This is why we see the drop off in production in batch distillation, as the ethanol concentration drops in the boiler. It takes more energy to vaporize water.

Cool video by the way Red!