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Flashcards for reviewing exothermic and endothermic reactions.
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What is an exothermic reaction?
A reaction that releases heat to the surroundings.
What is an endothermic reaction?
A reaction that absorbs heat from the surroundings.
What does a negative ΔH value mean in a thermochemical equation?
It indicates that the reaction is exothermic, meaning heat is released.
Why is photosynthesis considered an endothermic reaction?
Because it requires energy (sunlight) to convert carbon dioxide and water into glucose and oxygen.
In an __ reaction, what happens to energy?
Energy is released to the surroundings.
In an __ reaction, what happens to energy?
Energy is absorbed from the surroundings.
The thermochemical equation for the combustion of methane, CH4 + 2O2 → CO2 + 2H2O, includes ΔH = -890kJ, indicating it is __.
Exothermic
Photosynthesis is an example of an __ reaction because it requires energy from sunlight.
Endothermic
In an exothermic reaction, the value of ΔH is __.
Negative
Which statement best describes an exothermic reaction?
It releases energy.
What does a positive ΔH indicate in a thermochemical equation?
The reaction is endothermic.
Which of the following is an example of an endothermic reaction?
Photosynthesis
The reaction 2H₂ + O₂ → 2H₂O, ΔH = -572kJ, is:
Exothermic
In which reaction would you expect the temperature of the surroundings to decrease?
Dissolving ammonium nitrate in water.