Chemical changes are __________.

• A. temporary, reversible and a new substance is produced.
• B. always accompanied by exchange of light.
• C. permanent, irreversible and a new substance is produced.
• D. never accompanied by exchange of light and heat energy.

Chemical changes are best described by option C: permanent, irreversible, and a new substance is produced. During a chemical change, the original substances undergo a transformation that results in the formation of different substances, and this process cannot be reversed easily.

Characteristics of Chemical Changes

• Permanence: Once a chemical change occurs, it typically cannot be undone.
• New Substances: The products formed are chemically different from the reactants.
• Energy Changes: These changes often involve energy exchanges, such as heat or light, but this is not a defining feature.

Examples of Chemical Changes

Common examples include:

• Rusting of iron
• Burning of wood
• Cooking an egg

In each case, the original materials change into new substances that cannot be reverted to their original forms.