Theoretical basics of Inorganic chemistry

Investigation into Conservation of Mass

Purpose of the work:

To discover and write the meaning of the Law of Conservation of Mass by observing the masses before and after a physical change and chemical change.

Materials:

·         2 Beakers

·         2 Ziploc Bags

·         Vinegar (10mL each)

·         Baking Soda (2 scoops each)

·         1 Electronic Balance

·         1 Scoopula

·         Safety Goggles

Procedure:

Part A: Baking soda (NaHCO₃) and vinegar (C₂H₄O₂) in a closed Ziploc bag

1.      Safety glasses were put on

2.      Ziploc bags were labelled “Ziploc bag 1” and “Ziploc bag 2”

3.      10ml of baking soda was measured into a small beaker.

4.      The measured 5,8ml of baking soda was poured into Ziploc Bag 1.

5.      15ml of vinegar was measured into a graduated cylinder.

6.      The measured 10ml of vinegar was poured into a clean beaker.

7.      The beaker of 10ml of vinegar was cautiously and carefully placed into Ziploc Bag 1 and then sealed. It was made sure that the beaker’s contents did not spill.

8.      The bag was placed on the balance and then the total mass of the bag, container and its contents, were measured and recorded.

9.      The vinegar add baking soda were gently mixed together by knocking over the beaker and letting the vinegar spill into the baking soda. The bag was not opened.

10.  Ziploc bag 1 was set aside until there were no bubbles, signaling that the chemical reaction was finished.

11.  The total mass of bag 1 and its contents were measured and recorded. It was made sure that the bag remained sealed the entire time.

Part B: Baking soda (NaHCO₃) and vinegar (C₂H₄O₂) in an open Ziploc bag

12.  Steps 3-9 were repeated with Ziploc Bag 2.

13.  The bag was immediately opened after mixing and set aside until there were no bubbles, signaling that the chemical reaction was finished.

14.  The total mass of the bag 2 and its contents was measured and recorded.

Questions:

1.      How did the mass of the baggie before reaction compare with the mass after reaction?

2.      If a change of mass was recorded, give a valid explanation that will account for this change.

3.      If a change of mass was not recorded, give a valid explanation that will account for this.

4.      What gas was produced by each of the reactions in this lab? Explain.

5.      What law is obeyed in this lab? Explain the meaning of the law in your own words.

6.      When the solutions were mixed, did a chemical change occur? What was the evidence in the observations?