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Two bodies at different temperatures are placed in contact. What happens?
AThermal energy flows from the cooler to the hotter
BThermal energy flows from the hotter to the cooler
CThermal energy stays put until one body is removed
DThermal energy is destroyed as the two temperatures meet
Answer & Solution
Correct answer: B. Thermal energy flows from the hotter to the cooler
1. Heat is the transfer of thermal energy between two bodies at different temperatures.
2. Molecules in the hotter body have the higher average kinetic energy.
3. Collisions pass that energy to the cooler body, so flow is spontaneous from hot to cold.
4. The hotter body cools and the cooler body warms.
5. Flow continues until both reach the same temperature, called thermal equilibrium.
_Source: OpenStax Chemistry (CC BY 4.0), Ch 5 "Thermochemistry", section 5.1 Energy Basics_
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