Which of the following is a chemical change that can occur when a liquid is heated?

• A. Decomposition of the liquid into new substances
• B. Increase in the liquid's viscosity
• C. Expansion of the liquid due to increased temperature
• D. Evaporation of the liquid into a gas

Answer: (A)

Verified step by step guidance

1. Understand the difference between physical and chemical changes. A physical change affects the form or physical properties of a substance without changing its chemical identity, while a chemical change results in the formation of new substances with different chemical compositions.
2. Analyze each option to determine if it represents a physical or chemical change:
3. - 'Increase in the liquid's viscosity' is a change in a physical property (viscosity) and does not produce new substances, so it is a physical change.
4. - 'Expansion of the liquid due to increased temperature' is a physical change because the liquid's volume changes but its chemical identity remains the same.
5. - 'Evaporation of the liquid into a gas' is also a physical change, as the liquid changes state from liquid to gas without altering its chemical composition.
6. - 'Decomposition of the liquid into new substances' involves breaking down the original substance into different chemical species, which is a chemical change.