Multiple Choice
Which of the following diagrams best represents the potential energy changes during an exothermic reaction?
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8. Thermochemistry
Endothermic & Exothermic Reactions
Multiple Choice
Which of the following processes is exothermic?
A
Melting of ice
B
Evaporation of water
C
Combustion of methane (CH_4)
D
Photosynthesis in plants
Verified step by step guidance1
Understand the definition of an exothermic process: it is a process that releases heat to the surroundings, resulting in a temperature increase outside the system.
Analyze the melting of ice: melting is a phase change from solid to liquid, which requires energy input to break the hydrogen bonds, so it is endothermic (absorbs heat).
Analyze the evaporation of water: evaporation is a phase change from liquid to gas, which also requires energy to overcome intermolecular forces, so it is endothermic (absorbs heat).
Analyze the combustion of methane (CH_4): combustion is a chemical reaction where methane reacts with oxygen to form carbon dioxide and water, releasing energy in the form of heat and light, so it is exothermic (releases heat).
Analyze photosynthesis in plants: photosynthesis is a process where plants absorb sunlight to convert carbon dioxide and water into glucose and oxygen, which requires energy input, so it is endothermic (absorbs energy).
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