Question 1

Which of the following is the best evidence that a chemical change has occurred when baking cookies?

Accepted Answer

A new aroma is produced and the dough turns brown.

Question 2

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

Accepted Answer

Ice melting into water.

Question 3

Which of the following best describes an exothermic reaction?

Accepted Answer

A reaction that releases heat to the surroundings.

Question 4

Which of the following is NOT evidence of a chemical change?

Accepted Answer

Melting of ice.

Question 5

Which law explains why the mass of reactants equals the mass of products in a chemical reaction?

Accepted Answer

Law of Conservation of Matter

Question 6

Which of the following chemical equations is balanced?

Accepted Answer

$$ \mathrm{2H_2 + O_2$ \rightarrow 2H_2O} $$

Question 7

Which type of reaction is represented by the equation $$ \mathrm{2H_2 + O_2$ \rightarrow 2H_2O} $$?

Accepted Answer

Synthesis

Question 8

When iron rusts, which type of chemical reaction is occurring?

Accepted Answer

Synthesis

Question 9

Which of the following best describes a precipitate?

Accepted Answer

A solid formed from two solutions during a reaction.

Question 10

Which of the following is an example of a double replacement reaction?

Accepted Answer

$$ \mathrm{$$AgNO_3$$ + NaCl \rightarrow AgCl + $$NaNO_3$$} $$

Question 11

Which of the following is a correct definition of an aqueous solution?

Accepted Answer

A solution where water is the solvent.

Question 12

Which of the following is a real-life example of an endothermic reaction?

Accepted Answer

Photosynthesis in plants.

Question 13

Which of the following best describes the role of a coefficient in a chemical equation?

Accepted Answer

It shows the number of molecules or moles of a substance.

Question 14

Which of the following is NOT a chemical reaction?

Accepted Answer

Melting of chocolate.

Question 15

Which of the following best describes the process of digestion in the human body?

Accepted Answer

A chemical change where new substances are formed.

Question 16

Which of the following is a sign that a chemical reaction has occurred during baking?

Accepted Answer

The dough rises and changes color.

Question 17

Which of the following is an example of a single replacement reaction?

Accepted Answer

$$ \mathrm{Zn + 2HCl \rightarrow $$ZnCl_2$$ + H_2$} $$

Question 18

Which of the following best describes the law of conservation of matter?

Accepted Answer

Matter cannot be created or destroyed in a chemical reaction.

Question 19

Which of the following is a correct example of a combustion reaction?

Accepted Answer

$$ \mathrm{CH_4$ + 2O_2 \rightarrow CO_2$ + 2H_2O} $$

Question 20

Which of the following is an example of a physical change that occurs in the kitchen?

Accepted Answer

Boiling water.

Chemical and Physical Changes: Foundations of Chemical Reactions

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