Chemical Reactions & Conservation of Mass

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.

Tags

NGSS.MS-PS1-5

NGSS.MS-PS1-2

Which of the following is true of the law of conservation of mass?

• The same number and type of each atom will always be present before and after a chemical reaction takes place.
• Some of the atoms present before the reaction will always be lost during a chemical reaction.
• Some of the atoms will always be changed into a different type of atom by a chemical reaction.
• During a chemical reaction, atoms will always be combined into much larger molecules.

Tags

NGSS.MS-PS1-5

Which of the following is the best description of the results of a chemical reaction?

• The substance seems to disappear after dissolving in water.
• The substance changes from liquid to solid at a low temperature.
• The reaction can be reversed to get back the original substance.
• A new substance with different properties is formed.

Tags

NGSS.MS-PS1-5

NGSS.MS-PS1-2

Endothermic reactions...

• release energy
• explode
• take in energy
• have higher energy in their reactants than the products

Tags

NGSS.MS-PS1-4

NGSS.MS-PS3-4

Exothermic reactions

• have higher energy in their products than their reactants
• release energy
• get cold
• are synthesis reactions

Tags

NGSS.MS-PS1-4

NGSS.MS-PS3-5

What type of reaction is shown below?
A + B --> AB

• Synthesis
• Decomposition
• Single Replacement
• Double Replacement

What type of reaction is shown below?
AB --> A + B

• Synthesis
• Decomposition
• Single Replacement
• Double Replacement

What type of reaction is shown below?
AB + X --> AX + B

• Synthesis
• Decomposition
• Single Replacement
• Double Replacement

What type of reaction is shown below?
AB + XY --> AY + BX

• Synthesis
• Decomposition
• Single Replacement
• Double Replacement

You can balance a chemical equation by changing the

• subscripts
• coefficients
• reactants
• products

Tags

NGSS.MS-PS1-5