Types of Reactions and Chemical Equations

What is the Law of Conservation of mass?

• Mass is created in a chemical reaction
• Mass is created in a physical change
• New chemicals formed from a chemical reaction have a larger overall mass than the original reactants
• Mass is never created or destroyed

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NGSS.MS-PS1-2

NGSS.MS-PS1-5

Matter can not be created nor destroyed: it can only be

• Destroyed a little bit
• Invisible
• Transformed, changed
• None of the above

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NGSS.MS-PS1-5

Students react baking soda & vinegar.
Which of the following would provide the evidence that the number of atoms present before a chemical reaction is equal to the number of atoms present after the chemical reaction?

• The mass of the plastic bag, baking soda, and vinegar before the reaction was equal to the mass after the reaction.
• Bubbles were produced during the reaction, which meant that a gas was being produced.
• The plastic bag did not change in any way, indicating that it was not involved in the reaction.
• The mass of the baking soda was exactly equal to the mass of the vinegar used to create the chemical reaction.

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NGSS.MS-PS1-2

NGSS.MS-PS1-5

Suppose a reaction were to happen in an open container in a lab. During the reaction, the scientist observes the chemicals bubble, and produce a gas. During the analysis the scientist notices that the reactants weighed 20 g when he started, and the product weighed 18 g. Explain what happened.

• His chemical reaction defied the law of conservation of mass

• The product destroyed mass during the reaction

• The reactants created matter during the reaction

• The gas that was produced was not able to be weighed since the container was open.

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NGSS.MS-PS1-2

NGSS.MS-PS1-5

A chemical reaction is balanced when

• both sides have the same elements
• Both sides have the same  number of atoms
• Same subscripts
• Same coefficients

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NGSS.MS-PS1-5

The number in front of a compound or element is a 

• Subscript
• Coefficient
• Superscript
• Charge

The number to the lower side of an element is a 

• Subscript
• Superscript
• Coefficient
• Charge

How many nitrogen atoms does NH₃ have?

• 1
• 2
• 3
• 4

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NGSS.MS-PS1-1

How many oxygen atoms are in this chemical formula?

• 6 oxygen atoms

• 2 oxygen atoms

• 3 oxygen atoms

• 4 oxygen atoms

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NGSS.MS-PS1-1

Mg + ___ HCl → MgCl₂ + H₂

• 1

• 2

• 3

• 4

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NGSS.MS-PS1-2

NGSS.MS-PS1-5