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When a substance absorbs thermal energy and warms up, the value of q is:
AAlways zero
BUndefined
CPositive
DNegative
Answer & Solution
Correct answer: C. Positive
1. The sign of q records the direction of heat flow relative to the substance.
2. If a substance gains thermal energy its temperature increases, so the final temperature is higher than the initial.
3. The difference between final and initial temperature has a positive value, and the value of q is positive.
4. A substance that loses thermal energy has a negative temperature difference and a negative q.
_Source: OpenStax Chemistry 2e (CC BY 4.0), Ch 5 'Thermochemistry', sections 5.1-5.3_
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