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Laboratory popcorns
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Materials

      Corn grain for popcorns.
      Becker.
      Alcohol lamp.
      Tripod.
      Metal net.
 
Compounds

      Kitchen oil.
      Ethyl alcohol.
 
Videos:  
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Pictures:  








Procedure

     1. Pour some oil in the becker. (the oil should cover the whole surface of the becker)

     2. Heat the becker with the alcohol lamp flame.

     3. Put some corn grains in the becker. (be careful handling hot glass and oil. They can cause burns)

     4. Cover the becker with a paper leaf. (this way the popcorns can't jump out of the becker!)

     5. Observe the popcorns exploding. Very nice!
 
Why?

With this experiment we can verify that the corn grains are like bombs! The corn grains are a rigid external layer called pericarpo with starch and water inside. When the temperature increases, the water expands and occupies a higher volume and, consequently, the pressure inside the pericarpo increases gradually. In a certain moment, the pressure is so high that the pericarpo doesn't hold the pressure and explodes! On the other hand, the starch suffers an abrupt expansion, forming a white and delicious solid porous. Taste it and you will see that I am right.





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