Conservation of Mass

By Accessible Science on Jan 29, 2014

Purpose:

To illustrate the law of conservation of mass that states that matter is neither created nor destroyed during a chemical change

Background information:

This is one of the classic experiments using baking soda and vinegar. The expansion of the balloon with gas provides a tactile experience as the gas is captured rather than being released into the air. The evidence of conservation of mass is supported by the collection of data, by weighing the masses of the reactants before and after the experiment.

Preparation:

Have students practice using talking scales or pan balances, funnels, and measuring of dry and liquid ingredients is helpful before undertaking this experiment. However this experiment also provides opportunities to practice those skills!

Materials

  • Tray
  • Baking soda
  • Vinegar
  • Balloon
  • Funnel
  • Approximately 20 oz. plastic bottle with small neck
  • Talking scale or pan balance
  • Measuring cups

Procedure

  1. Measure about ¼ cup vinegar into a balloon. Placing the balloon in a beaker to hold it and using a funnel makes it easier to pour into the balloon. This part of the activity probably will require an extra set of hands to be sure no vinegar is spilled out of the balloon after it is filled.
  2. Measure ¼ cup baking soda into the plastic bottle. Using a dry funnel is also helpful here.
  3. Attach the balloon to the top of the plastic bottle, letting the balloon hang down to one side, so that no vinegar is coming in contact with the baking soda.
  4. Find the total mass of the container, balloon, baking soda and vinegar, and record the data.
  5. Lift up the balloon and the vinegar will pour into the container and mix with the baking soda. A chemical reaction will take place.
    Write equation here
    The force of the gas entering the balloon may have enough force to separate the balloon from the bottle so holding the balloon onto the neck of the bottle is advised! Hold the other hand on the expanding balloon.
  6. When the reaction has ceased, measure the total mass of the balloon, bottle, set up. Record the data and compare this mass to the mass before the reaction. The numbers should be very close.

conservation collage

 

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