Unit 3 Law of Conservation Lab AHS Instructor Ms. Kasia Room 109

NAME:______DATE:______

Unit 3 Law of Conservation Lab AHS Instructor Ms. Kasia Room 109

TOTAL POINTS /25

Laboratory Conduct (the student kept the work area clean and exhibited exemplary laboratory discipline) /5

Procedure (the student correctly followed the procedure, and complete the data collection section) /10

Discussion Questions (the student completed the questions showing appropriate work) /10

Law of Conservation Lab

INTRODUCTION No matter how things change, some things just stay the same. This idea is seen in the Law of Conservation of Mass, which will be investigated in this lab. Even when there is a chemical change, all the atoms at the beginning are still present at the end; they are simply rearranged. In this lab, you will be looking at a chemical change involving copper salts, which are responsible for the beautiful colors of gemstones such as azurite and turquoise. While observing this reaction, you will also be determining if mass if conserved.

MATERIALS

Triple beam balance

100mL beaker

Large Ziploc bag

Small Ziploc bag

Goggles

Potassium Bitartrate (KC4H5O6)

Hydrogen Peroxide (H2O2)

Copper Sulfate (CuSO4)

PROCEDURE

1. IN THE LARGE ZIPLOC BAG:

o  Measure ½ teaspoon of potassium bitartrate into the LARGE Ziploc bag.

o  Measure about 25 mL of hydrogen peroxide into the 100mL beaker and pour it into the LARGE Ziploc bag.

o  Mix these two ingredients well by kneading the outside of the bag with your fingers.

2. IN THE small ZIPLOC BAG:

o  Pour 1 teaspoon of copper sulfate solution into the small Ziploc bag.

o  Seal the small bag completely, and place it upside-down inside the LARGE bag.

o  Seal the LARGE Ziploc bag with the small Ziploc bag inside it.

o  Weigh the LARGE-small Ziploc bag combo on the triple beam balance. Record this mass in the table in the Data Collection and Analysis Section to the nearest 0.1 grams.

3. REACTION:

o  Without opening the LARGE bag, open the small bag from the outside and pour the copper sulfate solution into the LARGE bag with the mixture of potassium bitartrate and hydrogen peroxide.

o  Observe the reaction that happens when these chemicals mix, but BE CAREFUL because the bag will get VERY HOT!!

o  Record your observations in the space in the Data Collection and Analysis Section. Write down everything that you noticed (anything that indicates whether this was a physical or chemical change).

o  Once the reaction is complete, weigh the bag again on the triple beam balance. Record this mass in the table in the Data Collection and Analysis Section to the nearest 0.1 grams.

o  Throw away the entire reaction, with the large bag still sealed, in the trash can at the front of the lab.

o  Clean your work area, including the baker you used.

DATA COLLECTION AND ANALYSIS

Table 1: Reaction Mass Data

Observations

DISCUSSION QUESTIONS

1. The change that occurred in the reaction was a chemical change. Cite two pieces of evidence that tell you that it is a chemical change.

a. ______

b. ______

2. Do your initial and final masses of the Ziploc bags demonstrate the Law of Conservation of Mass? Why or why not?

3. If the lab had been done in a beaker instead of in Ziploc bags, what would be different? Would the results (initial and final masses) have been the same? Why or why not?

4. Percent Error Calculation

The mass before the reaction should equal to the mass after the reaction. Calculate the percent error you encountered.

5. Explain why you encountered this Percent Error.