Characteristics Of Chemical Reactions Pretest

Sodium and Chlorine react to form salt. At an atomic level, how do we know that a chemical reaction has occurred?

• Salt molecules are negatively charged.

• For every two sodium atoms, two chlorine atoms are needed.

• The sodium and chlorine atoms rearrange to form a new molecule.

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NGSS.MS-PS1-2

NGSS.MS-PS1-5

Which statement is true?

• Combining Substance A and B resulted in a chemical reaction because the temperature did NOT change.

• Combining Substance C and D resulted in a chemical reaction because the temperature did NOT change.

• Combining Substance A and B resulted in a chemical reaction because a gas was formed.

• Neither combinations resulted in a chemical reaction because none of them changed color.

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NGSS.MS-PS1-2

NGSS.MS-PS1-5

Which statement is TRUE?

• Cutting paper is an example of a chemical reaction because a new substance is formed and the process cannot be undone.

• Burning paper is an example of a chemical reaction because a new substance is formed and the process cannot be undone.

• Freezing water is an example of a chemical reaction because a new substance is formed and the process cannot be undone.

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NGSS.MS-PS1-2

A student see's bubbles begin to form within a mixture. the student believes this is a good sign that a chemical reaction has taken place. Explain why the bubbles are good evidence of a chemical reaction.

• Bubbles are cool.

• Bubbles are evidence of a chemical reaction because they indicate the presence of air.

• Bubbles are REALLY cool

• Bubbles are evidence of a chemical reaction because they indicate that a new substance (gas) has formed.

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NGSS.MS-PS1-2

Chemical reaction or not?

• yes

• no

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NGSS.MS-PS1-2

Is dissolving crystals/powder evidence of a chemical reaction?

• yes

• no

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NGSS.MS-PS1-2

Hint: gas bubbles are being produced. Chemical reaction or not?

• yes

• no

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NGSS.MS-PS1-2

NGSS.MS-PS1-5

Glow stick has been cracked. Chemical reaction or not?

• yes

• no

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

Hint: Bike is rusting. Is this a chemical reaction?

• yes

• no

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

Which observation is NOT evidence that a chemical reaction took place?

• Crystals dissolve

• A precipitate forms

• The bottom of the beaker feels warm to the touch

• Bubbles begin to form in the water

• Light forms

Tags

NGSS.MS-PS1-2