Chemical Reactions Pretest

Substances that exist before the reaction.

• reactants

• products

• coefficients

• precipitates

A change that results in a new substance that has properties different from the original.

• product

• chemical reaction

• physical change

• chemical change

Substances that are formed by the reaction.

• precipitate

• subscripts

• products

• reactants

Which of the following is an example of a physical change?

• temperature change

• unexpected color change

• change in size

• formation of a gas (bubbles)

Which of the following is an example of a chemical change?

• a change in color

• changing states of matter

• formation of a precipitate

• a change in shape

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.

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.

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.

Chemical reaction or not?

• yes

• no

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.