Worksheet

Atoms in the Kitchen: Models for Cooking, Cooling and Mixing

Grade 7 physical science: use formulas and atom models of kitchen substances to compare molecules, mixtures and extended structures while cooking and chilling.

Grade 7ScienceInteractive · Printable

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Single worksheet
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1 NGSS standard
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10 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, Sorting, Short answer

About this worksheet

What students practice

Students use formulas and atom models to describe the atoms in simple and large molecules.
Students tell molecules from extended structures and use models to describe mixtures and cooled or boiling substances.

How to use

Read paragraphs 2–4 together and have students sketch one molecule and one extended structure before they start. Ball-and-stick kits help with the counting questions.

Curriculum

NGSS standard covered

MS-PS1-1

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

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Name Date

Atoms in the Kitchen: Models for Cooking, Cooling and Mixing

Use atom models to compare molecules, mixtures and extended structures in a home kitchen.

Molecules in the pantry

Read the passage and Odile's chart, then answer the questions.

Saturday Breakfast, Atom by Atom

1Odile Brennan, a seventh grader, cooks Saturday breakfast with her grandfather, Mr. Ruben Castellano, a retired cook who keeps every jar and box in the pantry labeled. This week her science class is studying models of atoms, so she made a chart of substances in the kitchen and sketched an atom model of each one. Her younger brother, Anselmo, asked questions the whole time, and she wrote them down to bring to class.

2Many substances are made of molecules. A molecule is a group of atoms joined together, and every molecule of a pure substance has the same kinds and numbers of atoms, joined in the same way. A molecule's formula tells how many of each kind of atom it has. Water, H₂O, has 2 hydrogen atoms and 1 oxygen atom. Some molecules are small, like water or carbon dioxide, CO₂, the gas in soda bubbles. Others are large: one of the main molecules in olive oil, triolein, has the formula C₅₇H₁₀₄O₆.

3Other substances are extended structures. Their atoms are joined in a pattern that repeats in every direction, so there are no separate molecules, and a crystal is one big connected piece. For these substances, the formula gives the ratio of atoms. In table salt, NaCl, there is 1 sodium atom for every chlorine atom. In baking soda, NaHCO₃, there are 1 sodium, 1 hydrogen and 1 carbon atom for every 3 oxygen atoms. Metals, such as the aluminum in foil and the copper on the bottom of a pot, are extended structures made of a single kind of atom.

4In a mixture, each substance keeps its own particles. When sugar is stirred into tea, the sugar molecules spread out among the water molecules but stay whole. In ice, H₂O molecules are held near each other in a repeating pattern, but they are not joined to each other the way the atoms inside a molecule are joined.

Odile's Kitchen Chart
Substance	Found in	Formula	Kind of model
Water	Kettle	H₂O	Molecules
Sucrose (table sugar)	Sugar bowl	C₁₂H₂₂O₁₁	Molecules
Glucose	Honey	C₆H₁₂O₆	Molecules
Acetic acid	Vinegar	C₂H₄O₂	Molecules
Triolein	Olive oil	C₅₇H₁₀₄O₆	Molecules
Sodium chloride	Salt shaker	NaCl	Extended structure
Baking soda	Pantry box	NaHCO₃	Extended structure
Aluminum	Foil	Al	Extended structure

One sucrose molecule has atoms in all. One triolein molecule has atoms in all.

Anselmo notices that if you divide each number in glucose's formula, C₆H₁₂O₆, by 3, you get acetic acid's formula, C₂H₄O₂. He says the glucose in honey and the acetic acid in vinegar must be the same substance. Which response fits the models best?

A. They are different substances, since their molecules have 24 and 8 atoms joined in different ways.
B. They are the same substance, since each glucose molecule is three acetic acid molecules stuck together.
C. They are different substances, since glucose is built from larger carbon atoms than acetic acid.
D. They are the same substance, since both have twice as many hydrogen atoms as carbon atoms.

Use paragraph 4. Odile sketches a model of a tiny drop of sweet tea: 3 sucrose molecules spread out among 60 water molecules.

The drop model has oxygen atoms and hydrogen atoms in all.

The kettle reaches a full, rolling boil, and large bubbles rise through the water. Which model of the gas inside the bubbles fits paragraph 2 best?

A. Air molecules pushed out of the kettle's metal bottom by the heat
B. Separate hydrogen and oxygen atoms that broke away from the water
C. Whole H₂O molecules, spread much farther apart than in the liquid
D. Water molecules that grew larger as the water got hotter and hotter

Mr. Castellano keeps a bottle of olive oil in the refrigerator, and it turns cloudy and thick. Which model of the cold oil fits the passage best?

A. The triolein molecules join to one another into one big network, like salt.
B. The cold splits each triolein molecule into smaller molecules of water and CO₂.
C. The triolein molecules shrink, so each one ends up with fewer hydrogen atoms.
D. Each triolein molecule is still C₅₇H₁₀₄O₆; the molecules pack closer together.

Pans, salt and baking soda

Use paragraphs 2 and 3 and Odile's chart.

Sort each kitchen substance by the kinds of atoms it has and the kind of model it fits.

Oxygen gas, O₂, in the kitchen airAluminum foilWater in the kettleTable salt in the shakerCopper on the bottom of a potCO₂ bubbles in a glass of sodaBaking soda in the boxNitrogen gas, N₂, in the kitchen air

One kind of atom, molecules	One kind of atom, extended	Two or more kinds, molecules	Two or more kinds, extended

Underline each formula that gives only a ratio of atoms in an extended structure, not the atoms in one molecule.

H₂ONaClC₁₂H₂₂O₁₁NaHCO₃CO₂C₂H₄O₂

Odile builds a model of a tiny piece of a baking soda crystal. Her model has 40 carbon atoms.

The model needs oxygen atoms, and it has atoms in all.

Anselmo draws four boxes of particles. Which box shows a mixture rather than a single pure substance?

A. A box with one kind of particle: H₂O molecules
B. A box of sucrose molecules spread among H₂O molecules
C. A crystal of Na and Cl atoms in a repeating pattern
D. A box with one kind of particle: C₂H₄O₂ molecules

10.

Anselmo says, "Vinegar's acetic acid and table sugar can't be made of the same kinds of atoms. One is a sour liquid, and the other is a sweet, white solid." Do you agree? Write a claim, use evidence from Odile's chart, and explain your reasoning using atom models.