Which of the following best describes the main difference between physical properties and chemical properties?

• A. Chemical properties are only observed at high temperatures, while physical properties are observed at room temperature.
• B. Physical properties always involve a change in composition, while chemical properties do not.
• C. Physical properties can be observed without changing the substance's chemical identity, while chemical properties describe the ability of a substance to undergo chemical changes.
• D. Physical properties are unique to each element, while chemical properties are the same for all substances.

Answer: (C)

Verified step by step guidance

1. Step 1: Understand the definition of physical properties. Physical properties are characteristics of a substance that can be observed or measured without changing the substance's chemical identity. Examples include color, melting point, boiling point, density, and state of matter.
2. Step 2: Understand the definition of chemical properties. Chemical properties describe a substance's ability to undergo chemical changes or reactions that transform it into different substances. Examples include flammability, reactivity with acids, and oxidation states.
3. Step 3: Compare the two types of properties. Physical properties can be observed without altering the substance's composition, while chemical properties involve changes that alter the substance's chemical structure.
4. Step 4: Evaluate the given options based on these definitions. Identify which statement correctly contrasts physical and chemical properties according to their fundamental nature.
5. Step 5: Conclude that the best description is: 'Physical properties can be observed without changing the substance's chemical identity, while chemical properties describe the ability of a substance to undergo chemical changes.' This accurately captures the main difference.