Chemical Reactions

Which lab experiments below describe a situation where a chemical change has occurred? Check all that apply.

• The baking soda and hydrochloric acid combined, and bubbles formed. 

• The baking soda absorbed the hydrochloric acid. 

• Some of the baking soda dissolved in the hydochloric acid.

• The hydrochloric acid evaporated, leaving only the baking soda. 

What key words, when present in a question about chemical reactions, might indicate a chemical change is occuring? Check all that apply.

• Bubbling

• Fizzing

• Dissolving

• Evaporating

• One of the original compounds came out of solution

• The solutions reacted chemically

• Some of the water froze into ice crystals

• Rapid evaporation of water occured, leaving a solid

• The shape of the coal changes

• Oxygen is present

• A new substance is produced

• Coal is made up of more than one element

What evidence can you use to infer that a chemical reaction has occurred here?

• A dark solid formed on the zinc metal

• The zinc metal remained silver-colored and shiny

• None of these

• A gas is present

• The total number of atoms remains unchanged

• The state of matter remains the same

• A brown gas is produced

How does a chemical change affect the composition of matter?

• Chemical change always changes the composition of matter.
• Chemical change always decreases the mass of the matter.
• Chemical change always increases the mass of the matter.
• Chemical change always changes the value of the matter.

Which of the following is NOT a clue that a chemical change has taken place?

• transfer of energy
• change in color
• change of state
• production of a gas

In a chemical change, how does the mass of the reactants compare to the mass of the products?

• The mass of the products is always greater than the mass of the reactants.
• The mass of the reactants is always greater than the mass of the products.
• The mass of the reactants is always equal to the mass of the products.
• It depends on the specific chemical change.