Lab: The Atomic Mass of Candium - LPS Puma Chemistry



Lab 3: The Atomic Mass of Candium

Background information:

Isotopes are different forms of the same element. Therefore, they have the same number of protons and electrons, but they each have a different number of neutrons. For example, think of the three isotopes of hydrogen:

o H-1 is “regular” hydrogen

o H-2 is called deuterium

o H-3 is known as tritium.

They are all types of hydrogen with only one proton in the nucleus and one electron in the electron cloud, but all three have different numbers of neutrons in their nuclei.

In this lab, the “element” is called Candium. The three types of candy you will use are M&Ms, Skittles, and Reese’s Pieces. You will call the three forms (isotopes) of Candium “M&Mium,” “Skittlium,” and “Reesium.”

Each isotope of an element has a mass with a natural percent abundance. The atomic mass of the element listed on the periodic table represents the masses of each isotope and their percent abundances (how much of all the existing element is of that isotope – think iPod analogy).

For every element, each atom of a given isotope has the same mass; however you know that each M&M does not have the same mass just like each skittle does not have the same mass. Thus, in this lab you will determine the average mass of one atom of each isotope of Candium.

The two main purposes of this lab are to use a Candium model to explain the concept of atomic mass and to analyze the “isotopes of Candium” and calculate its average atomic mass.

Comprehension Questions:

1. What is different about the three isotopes of hydrogen?

2. What is one purpose of this lab?

Safety Requirements:

Do not eat the candies before, during or after the experiment. Contamination has occurred in this lab. You must return your back with the exact number of “atoms” that you received.

Materials:

- Sample of “Candium” - Calculator

- Electronic balance - Weighing tray

Procedure:

1. Obtain a sample of Candium from your teacher and record the Bag # in the box below.

2. Separate the three isotopes (M&Mium, Skittlium, and Reesium).

3. Measure the mass of each isotope. Record in Row 1 of Data Table

4. Count the number of atoms of each isotope by counting the number of M& M’s, Skittles, and Reese’s Pieces. Record in Row 2 of Data Table.

Data:

| |Isotope: |Isotope: |Isotope: |Total |

| |M&Mium |Skittlium |Reesesium | |

|[Row 1] | | | |X |

|Total Mass | | | | |

|of Atoms (g) | | | | |

|[Row 2] | | | | |

|Total Number of Atoms | | | | |

|Average Mass (g) | | | |X |

|(Row 1/Row 2) | | | | |

|4. Percent Abundance (%) | | | |X |

|(Box 2/Total Atoms) | | | | |

Analysis: Show at least one sample set-up in lab report notebook for each type of calculation for #1 and #2.

1. Calculate the average mass for each isotope (answers in row 3)

Average Mass = total mass of atoms

total number of atoms

2. Calculate the percent abundance of each isotope (answers in row 4)

% Abundance = number of particles of isotope x 100

total number of particles

3. Calculate the average atomic mass of this element, Candium.

Average atomic mass of Candium =

4. In box ‘3D’ in your data table, you calculated a number called the total “average mass.” How does this number compare to the average mass you calculated in Analysis Question #3. Which one is more accurate, and why? Why is the one you did not chose inaccurate?

5. If the isotopes of Candium were truly isotopes (not candy pieces), what characteristics would they have in common? What would be different about each isotope?

6. Get the average atomic mass of Candium from two other groups. What are at least two reasons why the average atomic mass of your Candium element that you calculated may not match the average atomic mass of any other lab group?

Group 1: __________________ Group 2: __________________

7. Is your calculated average atomic mass for Candium closest to one the average mass of one of your “isotopes”? Explain why.

9. The four isotopes of lead and its abundances are: Pb-204, 1.37%; Pb-206, 26.26%; Pb-207, 20.82%; and Pb-208, 51.55%. Calculate lead’s approximate average atomic mass.

GRIT: A laboratory finds four isotopes of iron below, but does not know the exact mass of the last isotope. Using the known mass on the periodic table, what is the mass of the last isotope?

Iron – 56 (91.75%) Iron – 58 (0.28%)

Iron – 57 (2.12%) Iron - ??? (5.85%)

Conclusion:

See the Lab Report grading guide on the next page for additional details on the rubric that will be used to grade your lab report.

Also, use the space below as an outline to draft your conclusion before you write it in paragraph format in your lab report.

Recall what your group did during this lab (briefly discuss the procedure)

Explain why you did this lab and what you were trying to find out (refer to the purpose). This should be no more than one sentence.

Reflect on the lab's meaning and your results (what did you determine). Show your data (average atomic mass) in this portion of the report and discuss its importance.

Uncertainty (discuss your % error and causes of the error. Think about human errors and experimental errors that you could change next time to increase the accuracy of your data)

New questions or new discoveries (list 2 questions or discoveries from this lab that you would want to do differently or ask if you were to repeat the lab again)

Use the following guideline that Mr. Sharar uses to grade your lab. Your lab report, should meet and surpass all the below expectations and requirements. You will not be penalized for mistakes that have been corrected. All straight lines (axes, best fit graphs, underlines, data tables) should be drawn with a ruler/straight edge.

Total: 50 pts.

I. Title, Date, (2 pts.)- Each lab must have a title and date at the top of a new page. The title should describe the lab in a couple of words. The date should be the date of the lab. Record the first and last names of each of your lab partners.

II. Purpose (2 pts.)- A sentence or two that describe why we are doing the lab, paraphrased from the handout and not copied.

III. Materials (1 pt) – List the materials that you used in this lab.

IV. Procedure (7 pts.)- A numbered list of steps describing the methods used to setup the experiment and gather data. Anyone who reads your report should be able to repeat the experiment just by reading your procedure. The procedure must always be in your own words and be specific instructions.

V. Data (8 pts.)- This is usually in table form, drawn with a ruler. These are the measurements you have made of the independent and dependent variables. Every number must be listed with appropriate decimal places and units (no “naked numbers”!).

VI. Analysis (15 pts.)- Here, this is referring to the analysis questions. Your numbers must be correct based on your data and all units must be shown. You need to show all work with correct steps and units. Box in your final answers. Analysis questions that ask for complete sentence responses must be grammatically correct, and the best answer are very specific and detailed.

VII. Conclusion (10 pts)- Generally 2 paragraphs (sometimes more, when needed) in which you summarize the experiment, state any key findings, and discuss sources of error. If you have a graph, you will explain what the graph means and what physical principle has been demonstrated. If the lab has prompts for the conclusion, be sure to address all prompts.

VIII. Neatness, grammar, clarity of writing, general appeal to the reader (5 pts.)

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Bag # _______

50

Letter

Grade:

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