Grade 8 · Science

8th grade Read a chemical formula and its ball-and-stick model worksheet

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Read a chemical formula and its ball-and-stick model

Grade 8 Science Worksheet - Challenge Me

NameDate

Circle the best answer.

1.
Ari draws 3 CO₂ for three carbon dioxide molecules from a big sigh. How many oxygen atoms do 3 CO₂ hold in all?
- 5 oxygen atoms
- 9 oxygen atoms
- 6 oxygen atoms
- 2 oxygen atoms
2.
On the board, Bo sees 2 NH₃, which means two ammonia molecules. How many hydrogen atoms do 2 NH₃ hold in all?
- 8 hydrogen atoms
- 5 hydrogen atoms
- 3 hydrogen atoms
- 6 hydrogen atoms
3.
Esme writes 4 H₂O for four water molecules in a very small puddle. How many oxygen atoms do 4 H₂O hold in all?
- 8 oxygen atoms
- 5 oxygen atoms
- 4 oxygen atoms
- 1 oxygen atom
4.
Jun's ethane model has 2 C balls in a row. Each C has 3 H balls on it. Sticks join every pair. Which formula matches?
- C₂H₆
- C₆H₂
- C₂H₇
- C₂H₃
5.
At camp, Kira's little stove runs on propane. The model has 3 C balls in a row; each end C has 3 H balls, the middle one 2. Which formula matches?
- C₃H₁₀
- C₈H₃
- C₃H₈
- C₃H₆
6.
Luz's butane model has 4 C balls in a row. Each end C has 3 H balls; each middle C has 2. Which formula matches the model?
- C₁₀H₄
- C₄H₈
- C₄H₁₀
- C₄H₁₃
7.
Milo says a CO₂ molecule has two carbon atoms, because of the 2 in the formula. Agree or disagree?
- Disagree: it has 3 carbon atoms
- Disagree: the 2 counts the oxygen atoms
- Agree: the 2 counts the carbon atoms
- Disagree: it has no carbon, as C has no number
8.
Pia reads 2 O₂ in a book and says it means 2 oxygen atoms in all. Agree or disagree?
- Agree: one O₂ has 2 atoms
- Disagree: it means 4 oxygen atoms
- Agree: the big 2 just repeats the small 2
- Disagree: it means 3 oxygen atoms
9.
Ren checks classmates' models of hydrogen peroxide, H₂O₂. Which model has the right balls?
- 3 balls: 2 lettered H and 1 lettered O
- 2 balls: 1 lettered H and 1 lettered O
- 4 balls: 1 lettered H and 3 lettered O
- 4 balls: 2 lettered H and 2 lettered O
10.
Tala is building ethylene, C₂H₄, to show the class. Which set of balls is right?
- 2 balls: 1 lettered C and 1 lettered H
- 8 balls: 2 lettered C and 6 lettered H
- 6 balls: 4 lettered C and 2 lettered H
- 6 balls: 2 lettered C and 4 lettered H

8th grade Read a chemical formula and its ball-and-stick model worksheet – printable — Print: 1 2 3 4 5 6

About this worksheet

Chemical formulas and ball-and-stick models. Every version has 10 questions, and the answer key prints on the second page.

What your child will learn

I can read a formula: each small number (subscript) counts the atoms of the symbol just before it, and no number means one atom.
I can match a formula to a ball-and-stick model and write the formula from a model.
I can count all the atoms in one or more molecules, using a big number in front (coefficient) when there is one.

Standard: MS-PS1-1

Words to know

chemical formula: Symbols and small numbers that show the atoms in a substance

symbol: One or two letters for an element; the first is always a capital

subscript: The small low number after a symbol: how many of that atom

molecule: A group of atoms joined together

ball-and-stick model: A drawing where balls are atoms and sticks are the bonds joining them

bond: The link that holds two atoms together, drawn as a stick

coefficient: A big number in front of a formula: how many molecules

Common mistakes

Your child treated a symbol with no small number as zero atoms. In H₂O, point to the O together: no number means one atom.

Your child gave a small number to the wrong element. In CO₂, the 2 belongs to the O just before it, so there are two oxygens and one carbon.

Your child counted the kinds of atoms instead of all the atoms. Count the balls of a model together, one ball at a time.

Questions parents ask

What is the most common mistake with read a chemical formula and its ball-and-stick model?

Your child treated a symbol with no small number as zero atoms. In H₂O, point to the O together: no number means one atom.

Are these 8th grade science worksheets free to print?

Yes. All 6 printable versions at each level are free to print, with the answer key, and no account is needed.

More grade 8 science

See all grade 8 science

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