Worksheet

What the Robot Smells: Models of Gases and Crystals

Grade 7 physical science: use particle models from a robot team's app to compare gas molecules, a mixture of gases and the extended structures of metal and sapphire.

Grade 7ScienceInteractive · Printable

Aligned toMS-PS1-1

Play online Play as a game

PrintLetter-size worksheet Answer keyPrintable answers

Assign to classAssign to your classes, or get a join code

What’s included

Single worksheet
Auto-graded online
1 NGSS standard
Printable answer key
9 questions
Classroom-ready

Details

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

About this worksheet

What students practice

Students use particle models to tell molecules, mixtures of molecules and extended structures apart.
Students count atoms in molecules and use the atom ratio of an extended structure.
Students explain why the same kinds of atoms can make different substances.

How to use

Have students sketch one or two of the boxes in Table 1 before they answer. Discuss the difference between a mixture and a pure substance before the final claim.

Curriculum

NGSS standard covered

MS-PS1-1

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

Preview

OwlSheets.com

Name Date

What the Robot Smells: Models of Gases and Crystals

Use particle models to compare the gases a robot senses with the solids it is built from.

The modeling app

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

A Robot With a Nose

1The robotics team at Juniper Flats Middle School built a delivery robot that rolls through the halls, carrying supplies from the front office to classrooms. This year, the head custodian asked the team to add an air sensor so the robot could also check the air near the boiler room on its rounds. Team captain Freya Lindqvist and programmer Chidi Anozie worked with their coach, Ms. Paloma Echeverría, to learn what the sensor would be "smelling."

2Everything around the robot is made of atoms. Some substances are made of molecules: small, separate groups of atoms joined together. In a gas, the molecules are far apart and move freely. The same kinds of atoms can be joined in different numbers or patterns, and each arrangement makes a different substance with its own properties. Other substances are extended structures. Their atoms are joined to neighbors in every direction, in a pattern that repeats out to the edges of the sample, with no separate groups. For an extended structure, a formula gives the ratio of the atoms, not a count of the atoms in one group.

3The team's sensor is built to detect carbon monoxide (CO), a gas with no color or smell that can make people sick. It can form when fuel burns without enough air, for example in a boiler that is not working well. The sensor is not set off by carbon dioxide (CO₂), the gas people breathe out.

4The robot's body is made of other substances. Its frame is aluminum, a metal. A thin window of sapphire covers its camera. Sapphire is a crystal made of aluminum and oxygen atoms, and it is so hard that grit from the hallway floor rarely scratches it. The team cleans the window with wipes that hold isopropyl alcohol, a liquid that evaporates quickly.

5Ms. Echeverría opened a modeling app that draws a box of particles from a sample. Each atom is a colored ball, and atoms that are joined touch each other. Table 1 lists what the app showed for six samples.

Table 1. What the Modeling App Showed
Box	Sample	Particles in the box	Atoms joined together
A	Hallway air	8 of one kind, 2 of another	8 have 2 N each; 2 have 2 O each
B	Carbon monoxide	10, all alike	1 C joined to 1 O
C	Carbon dioxide	10, all alike	1 C joined to 2 O
D	Isopropyl alcohol vapor	10, all alike	3 C, 8 H and 1 O
E	Sapphire window chip	No separate groups	Al and O, 2 Al for every 3 O
F	Aluminum frame shaving	No separate groups	Al only, in stacked layers

In Boxes E and F, every atom is joined to neighbors in every direction, and the pattern repeats out to the edges of the sample. Hallway air also holds small amounts of other gases, too few to show up in a box of only 10 particles.

Use Table 1 and paragraph 2. Sort each box by what its model shows.

Box A, hallway airBox B, carbon monoxideBox C, carbon dioxideBox D, isopropyl alcohol vaporBox E, sapphire window chipBox F, aluminum frame shaving

One kind of molecule	Two or more kinds of molecules	Extended structure

Use Box D.

The 10 particles in Box D hold atoms in all, and of them are hydrogen atoms.

The sensor beeps for carbon monoxide but not for carbon dioxide. Use Boxes B and C. Why are they different substances, even though both contain only carbon and oxygen atoms?

A. Carbon dioxide particles contain a third kind of atom that CO particles do not have.
B. The carbon atoms in carbon monoxide are a harmful kind of carbon atom.
C. Each CO particle has 1 oxygen atom joined to its carbon, but each CO₂ particle has 2.
D. Carbon monoxide is a mix of loose carbon atoms and loose oxygen atoms.

Freya wipes the camera window, and the isopropyl alcohol evaporates. Which model of the evaporating alcohol fits Box D and paragraph 2?

A. Each molecule splits into separate carbon, hydrogen and oxygen atoms that drift away.
B. The molecules stay whole, each with 12 atoms, and spread far apart in the air.
C. The molecules join end to end into one long chain that floats above the window.
D. The molecules lose their carbon atoms and turn into water molecules in the air.

Frame, window and test gas

Use Table 1 and the passage to answer the questions.

Use Box E. A tiny chip of the sapphire window has 10,000 atoms in all.

The chip has aluminum atoms and oxygen atoms.

The frame (Box F) and the window (Box E) both contain aluminum atoms. Which difference in the models best explains why they are different substances?

A. The window's pattern also has oxygen atoms, 3 for every 2 aluminum atoms.
B. The window is made of separate molecules, while the frame has none.
C. The frame's atoms repeat in a pattern, while the window's atoms do not.
D. The window's aluminum atoms are larger than the frame's aluminum atoms.

Chidi's first drawing of the frame shows aluminum atoms in separate pairs, like the N₂ particles in Box A. Which change would make his drawing match Box F?

A. Spread the pairs farther apart so that they can move around freely.
B. Join each aluminum atom to neighbors on all sides, with no separate pairs.
C. Join the pairs into separate groups of 12, like the particles in Box D.
D. Add oxygen atoms between the pairs, 3 for every 2 aluminum atoms.

To show how the sensor will be tested, Ms. Echeverría makes a model box that holds 6 CO molecules and 4 CO₂ molecules.

The box holds carbon atoms and oxygen atoms.

Freya says, "Hallway air is one substance made of air molecules, just like Box B is made of carbon monoxide molecules." Do you agree? Write a claim, use evidence from Table 1 and the passage, and explain your reasoning with the particle models.