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Flammable Liquid (Scantlin)

Author

Shayleen Scantlin

Principle(s) Illustrated

  1. Flammability
  2. High Specific Heat of water

Standards

  • Grade 6 Earth Science: 3b.Students know that when fuel is consumed, most of the energy released becomes heat energy.

  • Grade 9-12 ChemistryChemical Thermodynamics 7 d. Students know how to solve problems involving heat flow and temperature changes, using known values of specific heat and latent heat of phase change.
  • Grade 9-12 Chemistry: Chemical Thermodynamics 7 c Students know energy is released when a material condenses or freezes and is absorbed when a material evaporates or melts.

Questioning Script

Prior knowledge & experience:

Students know that paper money can eaisly burn if caught on fire. They also know that alcohol is a flammable liquid. 

Root question:

If this money catches on fire will it burn after soaking in a solution of water and alcohol?

Target response:

The money will catch on fire but will not burn. 

Common Misconceptions:

Many people would think that the money would burn compltetly because it does catch on fire. Other people may also think that the money will not catch on fire at all because it is wet. 

Procedure: 

Make a solution of 50% alcohol to 50% water. If you are using 70% isopropyl alcohol then there is already 30% of water. In that case you would need to use 70 mL of alcohol and 40mL of water. Make sure you stir the solution thoroughly to mix them.

Then put the money in the solution and let it soak it up.

After the money is damp take it out and out it over a flame.

The alcohol will burn a nice blue color and then will go out once it has all burned. To the students amazement the money will not burn. Alcohol, which has a high vapor pressure, will remain on the outside of the bill and is what burns. The heat from this fire is not hot enough to evaporate the water that the paper bill absorbed.  This is because the water absorbed into the bill and it has such a high heat capacity that it will not dry out the bill with the little bit of heat that the alcohol put off. 


Extensions: 

You also can boil water in a paper cup. The paper part of the cup will burn but wherever the water is it will not catch on fire. 

You also can light the water and alcohol solution on fire and the top layer of the water will burn. It will burn until the alcohol is all burned up and then the water will put it out. 

Photographs and Movies


YouTube Video

YouTube Video


References

Helmenstine, A. Burning Money- Chemistry Demnstration. About.com Guide. 2011. http://chemistry.about.com/od/demonstrationsexperiments/ss/burnmoney.htm 

Hubb. How to Light Money or Your Hand on Fire Without It Burning
http://cocopreme.hubpages.com/hub/MagicTrickLightingMoneyorYourHandonFireWithoutItBurning
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