Lab: The Atomic Mass of Candium



Lab: 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).

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 an isotope and what is different about the isotopes of Hydrogen?

2. What is one purpose of this lab?

How to calculate average Atomic Mass

Average Atomic Mass =

Example #1

Find the average atomic mass of carbon (C).

|Atomic Mass |Percent abundance |

|12.0 |98.90 |

|13.0 |1.10 |

Example #2

Find the average atomic mass and determine which element this data is for.

|Atomic Mass |Percent abundance |

|27.0 |92.23 |

|29.0 |4.67 |

|30.0 |3.10 |

Plan of Attack

In order to determine the average atomic mass of an element, what information will you need to collect? [Hint: look at the equation]

| |M&Mium |Skittlium |Reesium |

| | | | |

| | | | |

| | | | |

| | | | |

| | | | |

| | | | |

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

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: |Overall |

| |M&Mium |Skittlium |Reesesium |Total |

|[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 |

| | | | | |

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 your 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 not candy pieces but actual atoms, 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 the average mass of M&Mium, Skittlium or Reesium? Explain why.

8. Calculate your percent error using the expected value from your bag from Mr. Sharar.

Pre-AP: 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%)

Candium Lab Report Rubric Total: 50 pts.

Format

I. Title - Each lab must have a title at the top of a new page. It should describe the lab in a couple of words.

II. Purpose - A sentence or two that describe why we are doing the lab. Sentence starter: “The purpose of this lab was to…”

III. Procedure - A step-by-step list of 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.

IV. Materials – A list of all materials used in the lab

V. Data Table – Use the exact table from the lab handout and fill in the boxes appropriately.

VI. Calculations – Show your work for calculating the average mass and percent abundance of each isotope, as well as the work for calculating the average atomic mass (#1-3)

VII. Discussion - Follow the outline below

Lab Report Discussion Structure Guide      LPS Richmond

|Paragraphs |Parts of each paragraph |Optional Sentence Starters |

|1. Intro. ¶ |Purpose |The purpose of this lab was to... |

| | |This lab relates to the things we have been learning in class because.... |

| |Procedure |In this lab we… |

| | |In order to complete this experiment we… |

| | |To conduct this experiment we... |

|2. Analysis ¶ |Data |We recorded that… |

| | |The data indicates… |

| | |As a result of _______, we determined that... |

| |Explanation |These results do/do not make sense because… |

| |Error |Our percent error was ____, which means that… |

| | |One source of error may have been… |

|3. Conclusion ¶ |Summary |To summarize… |

| | |In conclusion… |

| | |In this lab we determined that… |

| |Future |This lab makes me wonder… |

| | |While our results demonstrate _______, I wonder what would happen if... |

| | |If we were to conduct this lab again, we would _______ because… |

| | |In the future, we could ______ because... |

Lab Report Rubric

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Bag # ____

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