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

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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
ItemSubstanceAtoms in the modelSeparate particles?
Hand sanitizerEthanol2 C, 6 H, 1 O in each groupYes: groups of 9
Water bottleWater2 H, 1 O in each groupYes: groups of 3
Climbing chalkMagnesium carbonate1 Mg : 1 C : 3 ONo
CarabinerAluminumAl onlyNo
Rope fiberNylon12 C, 22 H, 2 N, 2 O per unitYes: long chains
SunscreenZinc oxide1 Zn : 1 ONo
1.

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

2.
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?
Question 2 options

Modeling the chalk

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

3.
Which formula fits the model of magnesium carbonate in Table 1?
Question 3 options
4.
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?
Question 4 options
5.

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

6.
Which model best describes the liquid chalk inside its bottle, before it is used?
Question 6 options
7.
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?
Question 7 options

Rope, carabiners and sunscreen

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

8.
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.

9.
Underline each item whose model has no separate particles, only a pattern that repeats out to the edges of the sample.

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?
Question 10 options
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?
Question 11 options
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.