24. Which of the following involves a chemical change?
Answer: C
Burning a sugar cube involves a chemical change.
When a sugar cube is burned, it undergoes a chemical change as it reacts with oxygen, resulting in the formation of new substances such as carbon dioxide and water vapor.
A) Crushing a can
Crushing a can is a physical change because it alters the shape and size of the can without changing its chemical composition. The material remains the same aluminum, and no new substances are formed.
B) Boiling water
Boiling water is also a physical change. While the water changes from a liquid to a gas (steam), it retains its chemical identity as H₂O throughout the process and does not produce any new substances.
C) Burning a sugar cube
Burning a sugar cube represents a chemical change. During combustion, the sugar reacts with oxygen, resulting in new compounds being formed, indicating a transformation in the chemical structure of the original substance.
D) Breaking a bottle
Breaking a bottle is a physical change since it changes the state of the glass from whole to broken pieces without altering its chemical composition. The glass remains the same material, merely in a different physical form.
Conclusion
The only option that describes a chemical change is burning a sugar cube, as it results in the creation of new substances. In contrast, the other options involve physical changes where the original substances maintain their chemical identity. This distinction highlights the nature of chemical reactions versus physical alterations.