My chemistry portfolio!

Law of Conservation of Mass

on January 14, 2013


Krystal Knight

January 8, 2013

Class D


Law of Conservation of Mass



-Law of Conservation of Mass is a relation stating that in a chemical reaction, the mass of the products equals the mass of the reactants.

-The real mass changes are when something more is added to the substance.  In this lab, the lead nitrate was added to the potassium iodide, changing the mass.  The apparent changes are the ones we see as obvious and may think the mass changes when it really does not. 

-When I mixed the solutions in activity 1, the liquid turned bright yellow.  However, the mass did not change.

-When the vinegar and baking soda combined, the reaction was foaming and the bag filling up with air.  This change did affect the mass because the air was added making the bag heavier.  You could let the air out and then mass the bag to account for the change. 

-The heating of the steel wool did affect its appearance.  When it got hot, the wool turned a blue color.  However, I did not get a change in mass.  The reason for no change in mass was due to the little pieces flying off while it was burning.

-The apparent changes in mass in experiments can be proved or disproved with just massing every material before and after the reaction happens. 

-To modify such experiments, the scientist should mass all substances and materials before doing anything with them.


            I have learned about the law of conservation of mass in this lab. The main thing that was important to take from doing these experiments was that the mass the the sunstance was the same before and after the reaction happened.  This refers to the products and reacants being equal in mass.  I have also learned how to account for changes in mass.  For example, during the steel wool over the burner, the mass was supposed to change.  Ours did not because we stuck the wool in the flame and little pieces came off, decreasing the mass.  I enjoyed doing the three experiments in this lab, and learned many things in the end. 

-Potassium Iodide and Lead Nitrate= 39.91 g before and after, no change in mass.

-Vinegar and Baking Soda= 198.9 g before, 198 g after.  .9 g change in mass.

-Steel Wool= 1.31 g before and after, no change in mass.

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