Learning objective
Distinguish exothermic and endothermic reactions using enthalpy change signs.
Read the explanation, check the common trap, then practise with flashcards and questions.
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Flashcards
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Questions
Topic
Energetics
Subtopic
Enthalpy change
Study support
Understand this objective
Quick explanation
Distinguish exothermic and endothermic reactions using enthalpy change signs
- This point belongs to Energetics, especially Enthalpy change.
- You need to be able to distinguish exothermic and endothermic reactions using enthalpy change signs.
- The key ideas to know are enthalpy change, endothermic, and enthalpy.
- Use the linked flashcards and practice questions to check recall, then practise applying the idea in an exam-style answer.
Key concepts
Why it matters
This objective helps connect Enthalpy change to exam-style questions, flashcards, and revision notes for Energetics.
Quick student answer
Which of the following reactions is exothermic?
Direct answer
D) CH4(g) + 2O2(g) → CO2(g) + 2H2O(l) ΔH < 0
Key terms
- Enthalpy (H): A thermodynamic quantity equivalent to the total heat content of a system, defined as H = U + PV, where U is internal energy, P is pressure, and V is volume.
- Standard Enthalpy Change (ΔH°): The change in enthalpy when one mole of a substance is formed from its elements in their standard states under standard conditions (298 K and 1 atm).
Common trap
Confusing exothermic and endothermic reactions: Remember that exothermic reactions release heat and have a negative ΔH, while endothermic reactions absorb heat and have a positive ΔH.
Related questions
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Flashcard prompts
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Revision tools
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Revision notestopic notes
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Open revision notesRelated learning objectives
- Define enthalpy change under constant pressure.
Enthalpy change
- Interpret reaction profile diagrams.
Enthalpy change
- Define standard enthalpy changes for formation, combustion and neutralisation where appropriate.
Enthalpy change
- Use q = mcΔT to calculate heat energy transferred.
Calorimetry and enthalpy measurements
- Convert calorimetry data into molar enthalpy changes.
Calorimetry and enthalpy measurements