Question 21

A cut of meat spoils when left out.

This scenario illustrates a chemical change as the composition of the meat alters due to microbial activity and the breakdown of proteins, leading to spoilage.

A) An ice cube melts into water.

This option describes a physical change, as the ice cube transitions from solid to liquid without any alteration to its chemical structure. The water formed retains the same chemical properties as the ice.

B) Droplets form on a cold glass cup.

This scenario also represents a physical change where water vapor condenses into liquid droplets on the surface of the glass. The chemical composition of the water remains unchanged throughout the process.

C) Water is boiled to water vapor.

Boiling water is another example of a physical change, where water shifts from a liquid to a gaseous state. The chemical identity of H2O is preserved during boiling, indicating no chemical transformation has occurred.

D) A cut of meat spoils when left out.

This is a clear example of a chemical change, as the meat undergoes decomposition through the action of bacteria and enzymes, resulting in a transformation of its chemical makeup and the creation of new substances.

Conclusion

The correct answer demonstrates a chemical change as it involves a fundamental alteration in the composition of the meat. In contrast, all other options depict physical changes where the chemical identities of the substances remain intact, highlighting the distinction between physical and chemical changes in matter.