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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

NameDate

Circle the best answer.

  1. Grapes are full of a sugar called glucose, C₆H₁₂O₆. Ari wants the total. How many atoms are in one glucose molecule?

    • 24 atoms
    • 432 atoms
    • 6 atoms
    • 3 atoms

  2. Bo's cake rises thanks to baking soda, NaHCO₃. How many atoms in all does the formula NaHCO₃ show?

    • 4 atoms
    • 5 atoms
    • 6 atoms
    • 3 atoms

  3. Jun's model has one ball lettered N joined to three balls lettered H. Which formula matches the model?

    • NH₃
    • NH₄
    • N₃H
    • NH

  4. Ethylene is a plant gas that helps a banana ripen. Kira's model of it has 2 C balls and 4 H balls. Which formula matches?

    • C₄H₂
    • CH
    • C₂H₄
    • C₂H₂

  5. Luz's model shows a C ball between two O balls, all in a straight line. Which formula matches the model?

    • Co₂
    • CO
    • CO₂
    • C₂O

  6. Lemons taste sour partly because of citric acid, C₆H₈O₇. Which describes one citric acid molecule, Noah?

    • 6 carbon atoms and 15 hydrogen atoms
    • 3 atoms: carbon, hydrogen and oxygen
    • 1 carbon, 6 hydrogen and 8 oxygen atoms
    • 6 carbon, 8 hydrogen and 7 oxygen atoms

  7. Symbol and name. S sulfur; Si silicon; O oxygen. Pia finds a clear quartz pebble. Quartz is silicon dioxide, SiO₂. What does the formula SiO₂ show?

    • 1 sulfur atom for every 2 oxygen atoms
    • 2 silicon atoms for every oxygen atom
    • 1 silicon atom for every 2 oxygen atoms
    • Sulfur, iodine and oxygen atoms

  8. Water is H₂O. The bottle on Ren's science shelf holds hydrogen peroxide, H₂O₂. Are they the same substance?

    • No: a different number of oxygen atoms
    • Yes: both have 2 hydrogen atoms
    • Yes: both are made of just hydrogen and oxygen
    • No: H₂O₂ has no hydrogen

  9. Tala writes ethylene, C₂H₄, and ethane, C₂H₆, side by side. Do the two formulas show the same substance?

    • Yes: both have 2 carbon atoms
    • Yes: both have carbon and hydrogen
    • No: they have different numbers of hydrogen atoms
    • No: C₂H₆ has more carbon atoms

  10. In Zee's book, oxygen gas is O₂ and ozone is O₃. Both are only oxygen. Are O₂ and O₃ the same substance?

    • Yes: one extra atom changes nothing
    • No: ozone has no oxygen in it
    • Yes: both are made of oxygen alone
    • No: their molecules have different numbers of atoms
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8th grade Read a chemical formula and its ball-and-stick model worksheet – printable
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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.

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