Chemistry for the gifted and talented: the second law of thermodynamics

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This activity aims to introduce the topic in a way that uses the students’ synthesis skills to piece together several pieces of information.

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The second law of thermodynamics
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Level

16-18 years

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Specification

Northern Ireland
- A/AS level
  - CCEA Chemistry
    - Unit A2 1: Further Physical and Organic Chemistry
      - 4.2 Enthalpy, entropy, and free energy
        4.2.2 recall that the balance between entropy change and enthalpy change determines the feasibility of a reaction;
        4.2.3 recall that entropy is a measure of disorder;
        4.2.4 calculate the standard entropy change, ΔSӨ, in a chemical reaction using standard entropy data;
        4.2.5 use the equation ΔG = ΔH - TΔS to calculate standard free energy changes;
        4.2.6 recall that processes are feasible when the free energy change is negative;
        4.2.7 recall that when the enthalpy change and the entropy change have the same sign, the feasibility of the process depends on the temperature, and calculate the temperature at which these processes start or cease to be feasible;
England
- A/AS level
Scotland
- Advanced Higher
  - SQA Chemistry
    - Inorganic and Physical Chemistry
      - Reaction feasibility
        Second and third laws of thermodynamics
        The Second Law of Thermodynamics states that the total entropy of a reaction system and its surroundings always increases for a spontaneous process.
        Heat energy released by the reaction system into the surroundings increases the entropy of the surroundings, whereas heat energy absorbed by the reaction system from the surroundings decreases the entropy of the surroundings.
Wales
- A/AS level
  - WJEC Chemistry
    - Unit 3: PHYSICAL AND INORGANIC CHEMISTRY
      - 3.7 Entropy and feasibility of reactions
        (a) entropy, S, of a system as a measure of the freedom possessed by particles within it and the increase in entropy towards a maximum for all natural changes
        (b) particles in a solid having much less freedom than those in a gas and that, other factors being equal, entropy increasing in the sequence S(gas) > S(liquid) > S(solid)
        (c) how to calculate an entropy change from absolute entropy values, ΔS = Sfinal – Sinitial
        (d) concept of Gibbs free energy change and how it is calculated using the relationship, ΔG = ΔH – TΔS
        (e) spontaneous reactions having a negative value for ΔG and how the effect of entropy change explains the spontaneous occurrence of endothermic processes

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