Investigation the Law of
Conservation of Mass-Energy

INTRODUCTION:

A scientific law describes a phenomenon of nature. One of the basic laws of science that concerns chemists is the law of conservation of mass-energy. This law states that mass (matter) and energy are always conserved in reactions and that their sum cannot be increased or decreased. Mass and energy can be converted from one form to another,
In this investigation you will use the scientific method to test the law of conservation of mass-energy. To test this law, you will carefully determine the mass of two compounds, called reactants, and allow them to react. After performing the steps in the procedure to your two products, you will then interpret your results to see if they support the law of conservation of mass-energy.

PURPOSE:

In this experiment you will
  1. measure the mass of compounds A and B,
  2. combine these two compounds and observe how they react,
  3. determine the mass of the products formed in the reactions, and
  4. interpret your results based on the law of conservation of mass-energy.

EQUIPMENT:

Goggles and apron
2 Beakers (250 mL)
Graduated cylinder
Electronic balance
Stirring rod
Hot plate
Beaker clamp
Funnel and filter paper

INSTRUCTIONS:

  1. Each person in your lab group must read every page in this online procedure. Along the way, there will be questions that you must answer.
  2. Designate one person in your group as the Data Recorder. This person should open the Google document Experiment 3 - The Law of Conservation of Mass-Energy for the approved answer template.
  3. When this Google document opens, sign in to your Google account.
  4. From the FILE Menu, choose Make a copy...
  5. From the FILE Menu, choose Rename...and rename the document as follows: Exp 3 - Period (1, 3, 6, or 8) - Group #.
  6. Share this document with the members of your group and with Mr. Skubis at HSTChemistry@gmail.com.
  7. As a group, answer all questions. Remember to use complete sentences and be mindful of grammar, spelling, and punctuation.
  8. REMEMBER: **Plagiarism** is a form of **Academic Dishonesty** which carries harsh consequences. DO YOUR OWN WORK!


PROCEDURE:

Using the data table in the accompanying Google Doc, RECORD OBSERVATIONS and/or DATA for each procedure step.
CAUTION: You will be working with unknown compounds. Avoid skin and eye contact. Do not inhale the fumes.
Goggles and aprons MUST be worn for this experiment.

  1. Turn on the hot plate so that it will warm up.
  2. Obtain a clean, dry 250 mL beaker and label it 1. Measure its mass to the nearest 0.01 g.
  3. Mass 2.00 g of compound A and place it in beaker 1. Now add 20 mL of distilled water to beaker 1 to dissolve compound A.
  4. Obtain another clean, dry 250 mL beaker and label it 2. Measure its mass to the nearest 0.01 g.
  5. To beaker 2 add exactly 1.99 g of compound B. Using the same method as in Step 3, add about 30 mL of distilled water to beaker 2 to dissolve compound B.
  6. Swirl the two solutions until the solids have dissolved. Warm the solutions gently if necessary.
  7. Add solution B slowly and in small portions to solution A. Stir continuously.
  8. Rinse beaker 2 with distilled water. Empty the washing into beaker 1. Repeat.
  9. Heat the contents of beaker 1 to the boiling point.
  10. Turn off the heat and let the solid material in the beaker settle. The solid material is called a precipitate.
  11. Measure the mass of a piece of filter paper to the nearest 0.01 g. Ask your teacher to show you how to fold the filter paper. Place the filter paper in a funnel and place the funnel in a support ring as shown in the diagram.
  12. Place the empty beaker under the funnel and decant the liquid into the funnel. Keep as much of the precipitate in the beaker as possible.
  13. Add 20 to 25 mL of distilled water to the precipitate, warm slightly, and swirl for about 30 seconds. Decant the liquid into the funnel as before.
  14. Again add about 20 mL of distilled water to the precipitate, warm, swirl, and decant into the funnel.
  15. When the filtering is complete, use forceps to remove the filter paper from the funnel and place it in the beaker with the precipitate. Let it dry overnight as directed by your teacher.
  16. Remove the water from the filtrate in the other beaker by warming the solution until the water has evaporated.
  17. When both beakers and precipitates are dry, measure their masses carefully.
  18. Place the solid product in beaker 1 into the trash. The contents of beaker 2 may be rinsed down the drain using plenty of water.


ANALYSIS

Use the table in the approved Google Document to organize your observations described in the procedure.

FOLLOW UP QUESTIONS

Write answers for the questions in the Google Document. Remember to use whole sentences. Pay close attention to grammar, spelling, and punctuation.