Unit 2: Conservation of Mass

Which of the following would be considered a chemical change?

• cutting paper

• chopping firewood

• burning a chocolate muffin

• sharpening a pencil

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NGSS.MS-PS1-2

NGSS.MS-PS1-5

Poor conductors of heat and electricity

• nonmetals

• metals

• metalloids

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NGSS.MS-PS3-3

NGSS.MS-PS3-4

These tend to be malleable

• nonmetals

• metals

• metalloids

In a chemical reaction, the atoms in the​ (a)   , which are left of the arrow, rearrange to form new​ ​ (b)   , which are to the right of the arrow. This is why the mass before the reaction​ ​ (c)   the mass after the reaction.

• reactants
• products
• is equal to
• chemical change
• less than

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NGSS.MS-PS1-5

Mr. Gibson conducts a chemical reaction and wants to know the number of hydrogen atoms in the products. Hydrogen only appears in the compound 2H₂O in the reactants. 

 

How many hydrogen atoms must be in the products?

• 2 hydrogen atoms in the products, because the total mass is conserved.

• 4 hydrogen atoms in the products, because the total mass is conserved.

• 6 hydrogen atoms in the products, because mass decreases from reactants to products.

• 8 hydrogen atoms in the products, because mass increases from reactants to products.

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NGSS.MS-PS1-5

Which properties best describe metals?

Select TWO (2) correct answers.

• Shiny

• Brittle

• Malleable

• Semiconductor

The reaction equation for photosynthesis in a plant is shown.

6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

How does this chemical reaction demonstrate conservation of mass?

• The number of carbon atoms is the same on both sides of the equation; the number of hydrogen and oxygen atoms decreases in the products.

• The number of carbon, hydrogen, and oxygen atoms is the same on both sides of the equation.

• The number of carbon and hydrogen atoms is the same on both sides of the equation; the number of oxygen atoms increases in the products.

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NGSS.MS-PS1-5

In the picture, which box on the right shows the correct products according to the Law of Conservation of Mass?

• A

• B

• C

• D

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NGSS.MS-PS1-5

In chemical reactions, what does the principle of conservation of mass mean?

• Matter is not created or destroyed.
• The total mass of the reactants is greater than the total mass of the products.
• The total mass of the reactants is less than the total mass of the products.
• Matter is not changed.
  

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NGSS.MS-PS1-5

Which of these laws describes the underlying scientific idea considered when balancing a chemical reaction equation?

• the Law of Chemical Reactions

• the Law of Conservation of Mass

• the Law of Mass-Action

• Newton’s Law of Universal Gravitation

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NGSS.MS-PS1-5