Which Changes Produce Chemical Reactions
Chemical Changes vs. Physical Changes
Chemical changes and physical changes are two types of processes that matter can undergo. While physical changes involve changes in the appearance of a substance without altering its chemical composition, chemical changes result in the formation of new substances with different chemical properties.
Identifying whether a change is chemical or physical can sometimes be confusing. Let's look at some examples to better understand the differences:
Examples of Changes
A. A stone fizzes and forms a gas when acid is dropped on it.
B. Lava cools and changes from a thick fluid to solid rock.
C. A large rock is crushed into gravel.
D. Limestone slowly dissolves in water and forms a cave.
Which of these changes produces a chemical change? Answer: A Explanation: Fizzing is and forming a gas is a chemical reaction whereas the rest are simply changing physically. Lava's composition is not changed when turning to rock. A rock being crushed is not changing chemically, only physically. Limestone continues to be limestone after dissolving in water and only physically changes forms into a cave. Also emitting gas is a key aspect of chemical reactions.