Activity - Conservation of Mass

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					Name_______________________                                                Period_________
Activity: Chemical Reactions - Conservation of Mass
Background:
Lavoisier formulated the “LAW OF CONSERVATION OF MASS”, which
states that matter can neither be created nor destroyed. During a chemical
reaction, atoms of the reactants are rearranged to form new substances
(products.) Because matter must be conserved, the total mass before and
after any change must remain the same. This can also be interpreted to
mean that the number of atoms before and after any reaction must be equal.
This is the basis for why and how we balance chemical equations.

Materials:
          1 l plastic bottle w/ cap                       Metal scoop
          Test tube                                       Steel Wool soaked in vinegar
          Electronic Balance                              1 - 250 ml Erlenmeyer flask
          4 “scoops” Baking Soda (NaHCO3)                 1 Balloon
          HCl (enough to fill test tube ¾ full)
Procedure:
Part 1 – Reaction in a Bottle
      1. Place 4 scoops of Baking Soda in the plastic bottle.
      2. Fill test tube ¾ full with Hydrochloric Acid.
      3. Carefully place test tube with acid into plastic bottle with Baking Soda and cap tightly.
      4. Mass plastic bottle and its contents.
      5. Tip bottle so acid is released and observe reaction.
      6. When reaction takes place mass plastic bottle and its contents again. Be sure you use
          the same scale.
Part 2 – Rusting Steel Wool
      1. Place a piece of steel wool soaked in vinegar and then dried in an Erlenmeyer flask.
      2. Cover flask with a balloon.
      3. Immediately measure the mass of flask and its contents.
      4. Mass flask again approximately 5 minutes before the end of class. Be sure you use the
          same scale.

Data/Observations:
                        Material                                             Mass
Part 1: Reaction in a bottle
Mass of bottle and contents before reaction
Mass of bottle and contents after reaction
Part 2: Rusting Steel Wool
Mass of flask, iron, and balloon before reaction
Mass of flask, iron, and balloon after reaction
Analysis:
1. What were the reactants in the “reaction in a bottle” experiment?
_____________________________________________________________________
2. What were the reactants in the “rusting steel wool” experiment?
________________________________________________________________

3. What were the products in the “reaction in a bottle” experiment?
_____________________________________________________________________
4. What were the products in the “rusting steel wool” experiment?
________________________________________________________________

5. What are 3 indicators that a chemical reaction has occurred?
      a. ________________________________________
       b. ________________________________________
       c. ________________________________________
6. The equation (reaction) of the “reaction in a bottle” experiment is:
                       NaHCO3 + HCl  NaCl + H2O + CO2
   If not already balanced, write the balanced equation:
   _________________________________________________________________________
7. The unbalanced equation (reaction) of the “rusting steel wool” experiment is:
                               Fe + O2  Fe2O3
   If not already balanced, write the balanced equation:
  _________________________________________________________________

Conclusion:
1. In the “reaction in a bottle” experiment, did your data support or not support the law of
   conservation of matter? Why or why not?



2. In the “rusting steel wool” experiment, did your data support or not support the law of
   conservation of matter? Why or why not?



3. Did you observe a physical or chemical change in the “reaction in a bottle”
   experiment? What is your evidence?



4. Did you observe a physical or chemical change in the “rusting steel” experiment?
   What is your evidence?

				
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