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IGCSE Chemistry Exothermic and Endothermic Reactions Notes

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Exothermic & Endothermic Reactions

Hover over the blanks to reveal the answers.

1. Exothermic Reactions

An ________ reaction transfers ________ energy to the ________, causing the temperature of the surroundings to ________.

2. Endothermic Reactions

An ________ reaction takes in ________ energy from the ________, causing the temperature of the surroundings to ________.

3. Enthalpy Change (?H)

The transfer of ________ energy during a reaction is called the ________ change, written as ________.
For exothermic reactions, ?H is ________.
For endothermic reactions, ?H is ________.

4. Activation Energy

Activation energy (Ea) is defined as the ________ energy that ________ particles must have in order to ________.

5. Bond Energy and Enthalpy

Bond breaking is an ________ process because energy is ________.
Bond making is an ________ process because energy is ________.
The enthalpy change of a reaction depends on the energy required to ________ bonds and the energy released when ________ bonds form.

Syllabus Objectives

CORE:

  • State that an exothermic reaction transfers thermal energy to the surroundings leading to an increase in the temperature of the surroundings
  •  State that an endothermic reaction takes in thermal energy from the surroundings leading to a decrease in the temperature of the surroundings
  •  Interpret reaction pathway diagrams showing exothermic and endothermic reactions

EXTENDED:

  • State that the transfer of thermal energy during a reaction is called the enthalpy change, ?H, of the reaction. ?H is negative for exothermic reactions and positive for endothermic reactions
  • Define activation energy, Ea , as the minimum energy that colliding particles must have to react
  • Draw and label reaction pathway diagrams for exothermic and endothermic reactions using information provided, to include:
  • (a) reactants
  • (b) products
  • (c) enthalpy change of the reaction, ?H (d) activation energy, Ea
  •  State that bond breaking is an endothermic process and bond making is an exothermic process and explain the enthalpy change of a reaction in terms of bond breaking and bond making
  •  Calculate the enthalpy change of a reaction using bond energies

Revision Notes

Free IGCSE Chemistry Notes Endothermic and Exothermic reactions 2024/2025/2026/2027/2028 Exams pdf

5.1.1-IGCSE-Chemistry-Endothermic-and-exothermic-reactions.pdf

5.1.2-IGCSE-Chemistry-Reaction-pathway-diagrams.pdf

5.1.3-IGCSE-Chemistry-Calculating-enthalpy-change-of-a-reaction.pdf 

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IGCSE Chemistry Revised Syllabus Notes[ 2023-2025 exams]

1-States of matter

2 Atoms, elements and compounds

3 Stoichiometry

4 Electrochemistry

5 Chemical energetics

6 Chemical reactions

7 Acids, bases and salts

8 The Periodic Table

9 Metals

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10 Chemistry of the environment

11 Organic chemistry

12 Experimental techniques and chemical analysis