Counting Atoms in Chemical Equations

Miss Millander explains counting atoms in chemical equations, emphasizing the law of conservation of matter, which states that matter cannot be created or destroyed. She demonstrates how to balance chemical equations by ensuring the number of atoms in reactants equals those in products. The video covers using coefficients and subscripts to count atoms and provides examples, including rust formation and a practice activity with water and sugar molecules.

What does the law of conservation of matter state?

• Matter can be created and destroyed.

• Matter can only be created, not destroyed.

• Matter can neither be created nor destroyed, only transformed.

• Matter can only be destroyed, not created.

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NGSS.MS-PS1-5

In a chemical reaction, what happens to the atoms involved?

• Atoms rearrange without being created or destroyed.

• Atoms are created.

• Atoms disappear.

• Atoms are destroyed.

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NGSS.MS-PS1-5

How do you ensure the number of atoms is conserved in a chemical equation?

• Change the coefficients.

• Change the subscripts.

• Only count the reactants.

• Ignore the hydrogen atoms.

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NGSS.MS-PS1-5

What does the subscript in a chemical formula indicate?

• Number of reactions.

• Number of atoms of each element in a molecule.

• Total number of elements.

• Number of molecules.

How many atoms of hydrogen are present in three molecules of hydrogen gas (H2)?

• Twelve

• Nine

• Six

• Three

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NGSS.MS-PS1-1

What is the total number of oxygen atoms in two molecules of rust (Fe2O3)?

• Two

• Four

• Six

• Eight

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NGSS.MS-PS1-1

How many iron atoms are there in one molecule of rust (Fe2O3)?

• Six

• Four

• Three

• Two

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NGSS.MS-PS1-1

If you have four molecules of water (H2O), how many oxygen atoms do you have?

• Six

• Two

• Eight

• Four

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NGSS.MS-PS1-1

For two molecules of sugar (C6H12O6), how many carbon atoms are present?

• Twenty-four

• Eighteen

• Twelve

• Six

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NGSS.MS-PS1-1

What is the correct calculation to find the number of hydrogen atoms in two molecules of sugar (C6H12O6)?

• 6 x 1

• 6 x 2

• 12 x 2

• 12 x 1

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NGSS.MS-PS1-1