Which of the following statements is true? a) Neither chemical nor physical changes involve a change in appearance. b) Both chemical and physical changes can involve a change in appearance. c) Only physical changes involve a change in appearance. d) Only chemical changes involve a change in appearance.

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Although it might not seem as obvious as physical changes, a chemical reaction or transformation can also involve a change in appearance. For example, when a blacksmith heats a piece of steel bar at 2500° F, the steel bar will change in appearance in two ways: its color will turn orange-red, and its edges will become more dull. These transformations in appearance are due to a chemical change caused by extreme temperatures.

Another common example of a chemical change is the formation of bubbles, which is caused by different levels of gas molecules in water. Leaving a glass of flat water in a warm room will lead to the formation of tiny bubbles, thus changing its appearance.

Physical changes will definitely change the appearance of matter. The most common example of both physical and chemical changes is the transformation of water into ice, or water into vapor.

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