Gizmos Student Exploration: Moles Answer Key (2025)

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Ma

Name: Lee Arthur Date:

Student Exploration: Moles
Directions: Follow the instructions to go through the simulation. Respond to the questions andprompts in the
orange boxes.
Vocabulary: atomic mass, Avogadro constant, conversion factor, dimensional analysis, mole, molar mass,molecular mass,
scientific notation, significant figures, unified atomic mass unit
Prior Knowledge Questions (Do these BEFORE using the Gizmo.)
1. In the image to the right, note a dozen eggs, a dozen donuts and a dozen roses.How
many of each item do you have?

12

2. Would a dozen of each object have the same mass?

No

3. Suppose you have a dozen carbon atoms, a dozen gold atoms, and a dozen iron atoms. Even though youhave the
same number of each, would you expect them all to have the same mass? Explain.

No the mass of each one should be different

Gizmo Warm-up
When counting roses, eggs, or donuts, a dozen is a good unit to use. If you are counting atoms,
however, a dozen is not much help. In the Moles Gizmo, you will learnabout a unit used to count
atoms.
On the AVOGADRO CONSTANT tab, place the copper (Cu) atom on the nano-balance on the
left, which will show the average atomic mass of copper rather than the mass of a single copper
atom.
1. What is the average mass of a copper atom?

63.546u

The unit “u” refers to unified atomic mass units. A single proton or neutron has a mass of approximatelyone atomic
mass unit. (Officially, 1 u is one-twelfth the mass of a C-12 atom.)
2. To gain an idea as to how many atoms are in a gram or so of copper, use the larger balance on the right. Press Add
atoms to put a scoop of atoms in the weighing dish, and keep adding until the balance registersbetween 1 and 2 grams.
If you don’t seem to be making much progress, adjust the exponent using the slider, which will make the scoop size
bigger. How many atoms did you need to add?

2.21

, Get the Gizmo ready:
Activity A:
● Select the AVOGADRO CONSTANT tab.
Molar Mass ● Turn on Show hints and check that Copper (Cu)
is selected.

Introduction: Since atoms are so tiny, chemists have devised a unit known as the mole. A mole represents amacroscopic
quantity of matter that can be used in the laboratory. One mole of any element has the same mass in grams as its atomic
mass in u.

Question: How many particles are in a mole?

1. Explore: Note the average atomic mass of copper on the nano-balance. Add atoms to the larger balance until it
registers the same number (in g) as the reading on the nano-balance (in u). Use the Exponent sliderto help get the
correct amount. Stop adding atoms when the readings on both balances match exactly (to the nearest 0.001 g).

How many atoms did you need to add?

6.02214076 x 10^23

2. Explore: Repeat the same procedure with carbon, then sulfur and aluminum.

A. For each element, how many atoms did youneed 6.0221 x 10 ^23
to add?

Same atoms needed
B. What do you notice about the number of
atoms in one mole?

3. Discover: In each case, you measured out one mole of atoms, since the mass of one mole of any element, in grams, is
equal to its atomic mass, in u. One mole of any element contains the same number of atoms, a number known as the
Avogadro constant.

What is the exact value of the Avogadro constant?

6.02214076 x 10^23

4. Illustrate: The Avogadro constant is so large it is normally written in scientific notation. To get an idea ofthe
enormity of the Avogadro constant, write it out in standard form. (You will need to move the decimal place to the
right 23 times, so you will need to add a lot of zeros!)

602,214,179,300,000,000,000,000

5. Compare: While the number of atoms in a mole is constant, the number of grams in a mole changes basedon the
element. The number of grams in a mole (g/mol) is known as its molar mass, and has the same