8.6E Bell Ringer

What does the Law of Conservation of Mass state about chemical reactions?

• The total mass of reactants must equal the total mass of products.

• New atoms are created in a chemical reaction.

• Atoms are lost when they change into different elements.

• The total number of molecules always stays the same.

Tags

NGSS.MS-PS1-5

Which of the following correctly explains why a balanced chemical equation supports the Law of Conservation of Mass?

• The number of atoms of each element stays the same before and after the reaction.

• The reactants always weigh more than the products.

• The molecules in the reactants break down and disappear.

• The number of atoms in the products must be less than in the reactants.

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NGSS.MS-PS1-5

NGSS.MS-PS1-2

In a chemical reaction, 40g of methane reacts with 160g of oxygen to produce carbon dioxide and water. What is the total mass of the products?

• 120g

• 160g

• 200g

• 220g

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NGSS.MS-PS1-5

NGSS.MS-PS1-2

A student is balancing a chemical equation and notices there are more oxygen atoms in the reactants than in the products. What should the student do?

• Add a coefficient in front of one or more compounds.

• Remove extra oxygen atoms from the reactants.

• Change the chemical formulas of the products.

• Delete reactants to match the number of products.

Tags

NGSS.MS-PS1-5

A burning candle appears to lose mass as it melts and burns. Why does this not violate the Law of Conservation of Mass?

• Mass is lost during the reaction.

• Mass is converted into energy.

• Some mass is released as gas into the air.

• The candle does not undergo a chemical change.

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NGSS.MS-PS1-5

NGSS.MS-PS1-2

Which of the following represents a correctly balanced equation?

• CH₄ + O₂ → CO₂ + H₂O

• CH₄ + 2O₂ → CO₂ + 2H₂O

• CH₄ + 4O₂ → CO₂ + 4H₂O

• CH₄ + O₂ → 2CO₂ + H₂O

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NGSS.MS-PS1-5

Photosynthesis follows the Law of Conservation of Mass because:

• It creates new oxygen atoms from sunlight.

• It rearranges carbon dioxide and water molecules into glucose and oxygen without changing the total number of atoms.

• It permanently removes carbon atoms from the atmosphere.

• It converts energy into new atoms.

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NGSS.MS-PS1-5

NGSS.MS-LS1-6

A student studies the reaction: Fe + O₂ → Fe₂O₃. If 112g of iron reacts with 48g of oxygen, how much iron oxide will form?

• 48g

• 112g

• 160g

• It cannot be determined.

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NGSS.MS-PS1-5

NGSS.MS-PS1-2

A scientist analyzes the reaction: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O. What does this equation demonstrate about conservation of mass?

• Mass is not conserved because new atoms are created.

• The number of atoms remains the same before and after the reaction.

• The total number of oxygen atoms decreases in the products.

• The reaction absorbs mass from the surroundings.

Tags

NGSS.MS-PS1-5

A student dissolves baking soda in vinegar inside a sealed flask. The reaction releases carbon dioxide bubbles. The student records the total mass before and after the reaction and finds no change. What does this demonstrate?

• The gas produced had no mass.

• The reaction absorbed mass from the air.

• Mass was conserved because the system was closed.

• The reactants were heavier than the products.

Tags

NGSS.MS-PS1-5

NGSS.MS-PS1-2