Question

part a
which observation is consistent with a chemical reaction occurring? why?
a. propane forms a flame and emits heat as it burns.
b. acetone feels cold as it evaporates from your skin
c. bubbling occurs when potassium carbonate and hydrochloric acid solutions are mixed.
d. heat is felt when a warm object is placed in your hand
match the words in the left column to the appropriate blanks in the sentences on the right.
is consistent
are formed
are not formed
is not consistent
during observation a (propane burns), new substances , so the observation
with a chemical reaction occurring.
during observation b (acetone evaporates from your skin), new substances , so the
observation with a chemical reaction occurring.
during observation c (bubbling occurs as solutions are mixed), new substances , so the
observation with a chemical reaction occurring.
during observation d (heat from an object is felt), new substances , so the observation
with a chemical reaction occurring.

Explanation:

• Observation A: When propane burns, it undergoes a combustion reaction. In a combustion reaction, propane reacts with oxygen to form new substances like carbon dioxide and water. So, new substances are formed, and this is consistent with a chemical reaction.
• Observation B: When acetone evaporates from the skin, it is a physical change. Evaporation is a phase - change process (from liquid to gas) of the same substance (acetone). No new substances are formed, so this observation is not consistent with a chemical reaction.
• Observation C: When potassium carbonate and hydrochloric acid solutions are mixed, they react. The reaction produces carbon dioxide gas (which causes bubbling), potassium chloride, and water. New substances are formed, so this observation is consistent with a chemical reaction.
• Observation D: When heat is felt from a warm object in the hand, it is a heat - transfer process. There is no chemical change (no new substances are formed). It is a physical phenomenon related to temperature difference and heat transfer, so this observation is not consistent with a chemical reaction.

Answer:

• During observation A (propane burns), new substances are formed, so the observation is consistent with a chemical reaction occurring.
• During observation B (acetone evaporates from your skin), new substances are not formed, so the observation is not consistent with a chemical reaction occurring.
• During observation C (bubbling occurs as solutions are mixed), new substances are formed, so the observation is consistent with a chemical reaction occurring.
• During observation D (heat from an object is felt), new substances are not formed, so the observation is not consistent with a chemical reaction occurring.