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Arnoldi
Chemistry
Atomic Theory
Beanium Laboratory: An Atomic Mass Simulation
Atoms of the same element that have different masses are known as
isotopes. The difference in mass between isotopes is the result of these
atoms having different numbers of neutrons. An example of this is the
element Uranium. Uranium has three isotopes, each with a different mass.
In addition, each isotope occurs in a different abundance in nature. When
we say that the mass of Uranium is 238.029 amu, we have taken into account
the mass and percent abundance of each isotope. The mass of Uranium is
close to 238 amu because the isotope of Uranium – 238 occurs most
abundantly. The remaining 0.029 amu is the result of the other two rare,
and heavier, isotopes.
In this activity we will not examine the isotopes of Uranium, or any
other real element, because we do not have equipment that can handle the
miniscule size of atoms. Instead, we will examine the isotopes of Beanium,
Bn. Please understand, Beanium is not a real element, just your chemistry
teacher’s idea of a joke. We’re playing with beans, plain and simple.
Our Beanium exists in three isotopic forms: white, speckled, and
brown. While real atoms of a particular isotope will always have the same
mass, Beanium beans will not. However, by calculating the average mass of
each isotope form, we can obtain fairly accurate data.
Several calculations will be utilized in this activity. The most
important is the equation for finding atomic mass. Remember,
Atomic Mass = (Mass of Isotope A) X (Percent Abundance of Isotope A) + ...
100
MATERIALS:
Beans
Evaporating Dish
Balance
SAFETY:
Goggles are not necessary for this experiment, however, these beans
may be covered with anti-fungal agents. This is not a problem unless you eat
them – or don’t wash your hands when you are finished with the activity. So,
wash your hands, AND DON’T EAT THEM! :-)
PROCEDURE:
1. Measure the mass of a clean, dry, evaporating dish. Record here: _______ g
2. Use the dish to obtain a sample of Beanium. Count the total number of
beans on your sample. Record that value here:
________ total beans
3. Separate the sample of beans into the three isotopes. Count the number
of speckled beans, white beans, and brown beans. Record here:
number of speckled beans =
____________
number of white beans =
____________
number of brown beans =
____________
4. Place the white beans into the evaporating dish. Find the mass. Record
here:
mass of white beans and evaporating dish =
__________ g
5. Place the speckled beans into the evaporating dish.
Record here:
mass of speckled beans and evaporating dish =
Find the mass.
__________ g
6. Place the brown beans into the evaporating dish. Find the mass. Record
here:
mass of brown beans and evaporating dish =
__________ g
7. Return the beans to the container. Return the evaporating dishes. Wash
your hands.
Arnoldi
Chemistry
Atomic Theory Part One
Beanium Write-up
DATA
Record all calculations to TWO decimal places!
1. What was the mass of the empty evaporating dish?
2. Mass of Beans
Bean Type
Fill in the following data table:
Mass of Beans
Mass of Beans
and Dish
Alone
________________ g
Number of
Beans
Average Mass
of a Single Bean
White
Speckled
Brown
How did you find the mass of the beans alone? Show your work for the white bean only.
Word Equation
Number Equation (circle final answer)
How did you find the average mass of a single white bean?
Word Equation
Number Equation (circle final answer)
ANALYSIS
1. What was the total number of beans in your sample?
________________
2. Fill in the following data table:
Bean Type
Number of Beans
Percent Composition
of Sample
White
Speckled
Brown
How can you find the percent composition of each bean? Show your work for the white bean only.
Word Equation
Percent Composition of White Bean
Number Equation (circle final answer)
=
Number of White Beans
Total Number of Beans
X
100
3. Use the two previous tables to fill in the following table:
Bean Type
Mass of a Single
Bean Only
Percent Composition
of Sample
White
Speckled
Brown
How can you find the average atomic mass from this information? Show your work below.
Word Equation
Average Atomic Mass of Beanium =
(Mass of a Single White Bean) (% Composition of White Bean)
+
(Mass of a Single Speckled Bean) (% Composition of Speckled Bean)
+
(Mass of a Single Brown Bean) (% Composition of Brown Bean)
100
Number Equation (circle final answer)
4. What was your actual value for the atomic mass of Beanium?
______________
5. The theoretical value for the mass of Beanium is 0.49 amu. What is the percent error
for this laboratory?
Word Equation
Number Equation (circle final answer)
CONCLUSION
Even though we took the average mass of each isotope, each group did not get exactly the
average atomic mass. Why?