Chemical Reactions Review

What happens in a chemical reaction?

• Bonds between atoms break and/or are formed

• New atoms are created and/or removed

• Protons move from one atom to another

• Electrons change into protons

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NGSS.MS-PS1-1

NGSS.MS-PS1-2

NGSS.MS-PS1-5

Which of the following would indicate that a chemical reaction has occurred?

• A new element has been created

• A different substance has formed

• The total mass has either increased OR decreased

• The total number of elements has either increased OR decreased

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NGSS.MS-PS1-2

NGSS.MS-PS1-5

Which would indicate a chemical equation is balanced?

• If the number of atoms in the reactants is the same as the number of atoms in the products

• If the atoms have ionic OR covalent bonds

• If the atoms have full valence shells

• If the total energy has remained the same

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NGSS.MS-PS1-2

NGSS.MS-PS1-5

What does the Law of Conservation of Mass state?

• No new substances can be made or destroyed

• No new compounds can be made or destroyed

• No new atoms can be made or destroyed

• Mass cannot be lost from a physical reaction

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NGSS.MS-PS1-5

Which of the following follows the Law of Conservation of Mass?

• CH₄ + 2 O₂ → 2CO₂ + 2 H₂O

• 2 CH₄ + 2 O₂ → CO₂ + 4 H₂O

• CH₄ + 2 O₂ → CO₂ + 2 H₂O

• All the above

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NGSS.MS-PS1-5

In a chemical reaction, ________________________ are changed into _______________________.

• Reactants; Products

• Electrons; Molecules/Compounds

• Coefficients; Subscripts

• Original Elements; New Elements

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NGSS.MS-PS1-2

NGSS.MS-PS1-5

Bacteria in milk causes it to curdle over time. What type of change is this?

• Chemical

• Physical

• Both

• Neither

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NGSS.MS-PS1-2

NGSS.MS-PS1-5

Which type of reaction pulls in thermal energy from the environment around it?

• Endothermic

• Exothermic

When building a HEATING pack, what type of reaction is it?

• Exothermic

• Endothermic

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NGSS.MS-PS1-4

NGSS.MS-PS3-3

During a lab experiment, a scientist numbers three beakers. Next, she pours 150 mL of  liquid into each beaker. Each liquid is different.Then, the scientist adds 5 g of white solid baking soda (NaHCO₃) to each beaker and stirs. She observes the results.
In which of the beakers does the scientist observe clear evidence of a chemical reaction?

• beaker 1 only
• beaker 2 only
• beaker 3 only
• beakers 1,2, and 3

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NGSS.MS-PS1-2