Jenna took an open bowl of leftover mashed potatoes from the refrigerator and noticed a difference in smell. She determined that chemical changes occurred since the potatoes were first placed there.

A change in odor is evidence that new substances may have formed, which indicates a chemical change. The potatoes cooled after being taken from the refrigerator, but a temperature decrease alone is a physical change. Changes in moisture content or mass can also happen without changing the potatoes’ chemical composition.

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