What Metal Makes a New Penny

Chemistry Name______Mr. Stanger / Mr. Lutz Block______Conservation of Mass

Lab Report Format:

Heading:

Chemistry Name______Teacher’s Name Block______

Conservation of Mass

The law of conservation of mass states that matter is neither created nor destroyed during a chemical reaction and that the mass of a system should therefore remain constant during any chemical process. This means that during any reaction the sum of the masses of the products of a reaction must be the same as the sum of the masses of the reactants. For example, imagine using a spark to ignite a match in a glass jar which is so tightly sealed that no matter can enter or escape. As the match burns, flammable substances from the match and some oxygen from the air are transformed into water, carbon dioxide and other substances. Measurements taken before and after the match burned would show that the total mass remains the same.

Although this concept may seem obvious, it was not always so. When early scientists first began exploring chemical changes, they frequently did not consider the effects of the air and other gases. Similarly, the equipment originally used often did not take into account the possibility that a gas could be a product or a reactant.

Purpose:

Relate observations of a chemical reaction to the law of conservation of mass. Design an experiment to support the law of conservation of mass.

Materials:

Part 1: Part 2:

Baking Soda (NaHCO3) Dependent on your design Vinegar Plastic Cups – 2 100 mL Graduated Cylinder Balance Goggles Apron Weighing Paper Page 1 of 3 0242389e2b463abc2cadb1c9e0a74634.doc 5/8/2018 Procedure:

Part 1:

1. Make a data table with four columns and three rows. Label the boxes in the first row of the second, third and fourth columns Initial Mass (g), Final Mass (g) and Change in mass (g). Label the boxes in the second and third rows of the first column Part 1 and Part 2. Below the table leave room for observations about the reactions.

2. Place a piece of weighing paper on the laboratory balance. Place approximately 5 grams of baking soda on the weighing paper. Carefully transfer the baking soda to a plastic cup.

3. Measure approximately 100 mL of vinegar. Pour the vinegar into the second plastic cup.

4. Place both cups on the balance, and determine the initial total mass of the system. Record the mass in your data table. (If the balance pan cannot hold both cups, measure the mass of one cup, and then the other. Add these masses to find the initial total mass of the system.

5. Take the cups off the balance. Slowly and carefully pour the vinegar into the cup that contains the baking soda. Gently stir or swirl the cup to make sure the reactants are well mixed. Record your observations.

6. When the reaction has finished, place both cups back on the balance to determine the final mass of the system. Record the final mass in your data table. Calculate any change in mass.

Part 2:

1. Develop a procedure that will test the law of conservation of mass more accurately than does the procedure in Part 1. When you think you have a plan, you must get your teacher’s approval before proceeding. (Hint: Do not use more than 50 mL of vinegar in this procedure.)

2. Implement your procedure. You may use the same quantity of baking soda as in Part 1. Record all data in your data table.

3. If you are successful in Part 2, your results reflect that mass is conserved. If mass was not conserved, redesign your experiment and repeat Part 2.

4. All products can be disposed of down the sink with water. Clean all equipment and your lab station. Thoroughly wash your hands after completing the lab work. Page 2 of 3 0242389e2b463abc2cadb1c9e0a74634.doc 5/8/2018 Questions:

1. What evidence did you observe that indicated a chemical change occurred in this experiment?

2. Was the law of conservation of mass really violated in Part 1? Explain your answer.

3. Explain why the results for Part 2 were different from those for Part 1.

4. What is the system in Part 1? What is the system in Part 2? How do they differ?

5. When a log burns, the resulting ash obviously has less mass than the log did. Explain whether this loss of mass violates the law of conservation of mass.

Grading Criteria:

. Word Processed with Correct Format (10 points)

. Correct Spelling Used with Complete Sentences (10 points)

. Purpose Correctly Stated (10 points)

. Materials Correctly Stated (10 points)

. Procedure Correctly Stated (10 points)

. Observations/Data Tables (20 points)

. Sample Calculations (can be hand written) (5 points)

. Analysis & Conclusions (25 points)

of 3 0242389e2b463abc2cadb1c9e0a74634.doc 5/8/2018