Worksheet

Chalk, Rope and Carabiners: Atom Models at the Climbing Gym

Grade 7 physical science: model the atoms in hand sanitizer, climbing chalk, liquid chalk, rope and carabiners, and judge which models show molecules or extended structures.

Grade 7ScienceInteractive · Printable

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Single worksheet
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1 NGSS standard
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12 questions
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Details

Format: Interactive · Printable
Grade: Grade 7
Subject: Science
Question types: Fill in the blank, Multiple choice, Circle the answer, Short answer

About this worksheet

What students practice

Students use model descriptions to count the atoms in molecules and in pieces of extended structures.
Students judge whether a model correctly shows a substance as separate molecules or as an extended structure.

How to use

If you have a molecule model kit, let students build the ethanol and chalk models before answering. Use question 12 to discuss the difference between a substance and a mixture.

Curriculum

NGSS standard covered

MS-PS1-1

Model the atoms in simple molecules and in extended structures such as crystals.

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Chalk, Rope and Carabiners: Atom Models at the Climbing Gym

Build and judge models of the molecules and extended structures in a climbing bag.

Molecules in the climbing bag

Read the passage and Table 1. Then answer questions 1–2.

What's in the Climbing Bag?

1The climbing team at Alder Point Middle School trains twice a week at a local climbing gym. Their coach, Ms. Thandiwe Mokoena, studied chemistry before she started coaching. Before the team's first competition, she gave climbers Paloma Iturbe and Viktor Hadžić a molecule model kit and a challenge: build models of the atoms in the things they carry in their climbing bags. In the kit, black balls stand for carbon atoms, white for hydrogen, red for oxygen, blue for nitrogen and gray for magnesium, and short sticks stand for the bonds that join atoms.

2The gel hand sanitizer the team uses is mostly ethanol and water. Each ethanol particle is a group of 9 atoms joined by bonds: 2 carbon, 6 hydrogen and 1 oxygen. The groups are separate from one another, so each group is one molecule.

3Climbing chalk is mostly magnesium carbonate. In it, each carbon atom is joined to 3 oxygen atoms in a small group called a carbonate group. These carbonate groups take turns with magnesium atoms in a pattern that repeats in every direction, out to the edges of each grain. There are no separate molecules: a bigger grain just has more of the same pattern. The team also uses liquid chalk, which is chalk powder stirred into ethanol. A climber rubs a few drops on her hands, the ethanol evaporates within a minute, and a thin white layer of chalk is left behind.

4The carabiners that clip the rope to the wall are made mostly of aluminum, with atoms packed in layers that repeat in every direction. The rope is woven from nylon fibers. Nylon is made of very long chain molecules. Each chain is built from a unit of 12 carbon, 22 hydrogen, 2 nitrogen and 2 oxygen atoms, repeated hundreds of times in a row. Each chain has two ends, and the chains lie close to one another without being joined like the atoms inside a chain. For an outdoor climbing trip, Paloma also packed a sunscreen made with zinc oxide, in which zinc and oxygen atoms take turns in a pattern that repeats in every direction.

Table 1. The Team's Model Cards
Item	Substance	Atoms in the model	Separate particles?
Hand sanitizer	Ethanol	2 C, 6 H, 1 O in each group	Yes: groups of 9
Water bottle	Water	2 H, 1 O in each group	Yes: groups of 3
Climbing chalk	Magnesium carbonate	1 Mg : 1 C : 3 O	No
Carabiner	Aluminum	Al only	No
Rope fiber	Nylon	12 C, 22 H, 2 N, 2 O per unit	Yes: long chains
Sunscreen	Zinc oxide	1 Zn : 1 O	No

One ethanol molecule has atoms. A model of 20 separate ethanol molecules needs black balls.

Viktor makes his first ethanol model by dropping 2 black, 6 white and 1 red ball loosely into a cup, with no sticks. What does his model fail to show that a model with sticks would show?

A. How many atoms of each kind are in one ethanol molecule
B. That the 9 atoms are joined together into one particle
C. That ethanol has more hydrogen atoms than carbon atoms
D. That ethanol is made of three different kinds of atoms

Modeling the chalk

Use paragraph 3 and Table 1 to answer questions 3–7.

Which formula fits the model of magnesium carbonate in Table 1?

A. MgCO₃
B. MgC₃O
C. Mg₃CO
D. Mg₃C₃O

Paloma builds a chalk model from 5 balls: 1 gray ball and 1 black ball, with 3 red balls around the black ball. She joins all five with sticks and labels it "one molecule of chalk." Which change would make her model match paragraph 3?

A. Repeat the same pattern in every direction, so it is a piece of a grain, not a molecule.
B. Join the gray ball to 3 red balls of its own, so each atom has the same number of sticks.
C. Take out all the sticks, so the gray, black and red balls sit loose next to each other.
D. Swap the black ball for a second gray ball, since chalk is made of only one kind of atom.

Viktor builds a chunk of the chalk pattern with 40 gray balls. His chunk needs black balls and red balls, for balls in all.

Which model best describes the liquid chalk inside its bottle, before it is used?

A. Loose magnesium, carbon and oxygen atoms floating among separate ethanol molecules
B. Tiny grains of the magnesium carbonate pattern, spread among separate ethanol molecules
C. Ethanol molecules joined by bonds to the chalk pattern, making one new network
D. Chalk molecules of 5 atoms each, spread out among separate ethanol molecules

A climber rubs liquid chalk on her hands, and a minute later only a dry white layer is left. Which model of what happened fits the passage best?

A. The carbonate groups left with the ethanol, and the magnesium atoms stayed on her skin.
B. The chalk grains turned into ethanol molecules, which then rose into the air.
C. Whole ethanol molecules moved off into the air, and the chalk pattern stayed on her skin.
D. The ethanol molecules broke into carbon, hydrogen and oxygen atoms that joined the chalk.

Rope, carabiners and sunscreen

Use paragraph 4 and Table 1 to answer questions 8–12.

Ignore the few extra atoms at the two ends of a chain.

One nylon chain has 200 units in a row. The chain has nitrogen atoms and atoms in all.

Underline each item whose model has no separate particles, only a pattern that repeats out to the edges of the sample.

Hand sanitizerClimbing chalkRope fiberCarabinerWater bottleSunscreen

10.

The team wants one model for the gym's display case that shows aluminum is an extended structure. Which model would show this best?

A. Two balls joined by one stick, labeled "Al₂"
B. A long row of balls with two ends, like a nylon chain
C. One large ball labeled "Al", set on a stand by itself
D. A block of many balls packed in layers right out to every edge

11.

Viktor says the rope is an extended structure, like the carabiner, because nylon repeats the same unit hundreds of times. Which evidence best shows he is wrong?

A. Each nylon unit has 22 hydrogen atoms, more than any other kind of atom.
B. Table 1 lists both nylon and aluminum as having no separate particles.
C. Each nylon chain has two ends and is not joined by bonds to the chains beside it.
D. Nylon contains four kinds of atoms, while the carabiner is mostly one kind.

12.

Paloma says, "Liquid chalk is one pure substance: chalk molecules dissolved in ethanol." Do you agree? Write a claim, use evidence from paragraph 3 and Table 1, and explain your reasoning with atom models.