Thermodynamics and Gibbs free energy take centre stage in this Grade 12 Science worksheet, where students calculate energy changes and use them to predict whether chemical reactions are thermodynamically spontaneous. Rather than treating spontaneity as a definition to memorise, the resource asks students to work with the relationships between enthalpy, entropy, temperature, equilibrium and energy transfer.

⚗️ From energy changes to reaction spontaneity

The reading passage introduces the first and second laws of thermodynamics in the context of chemical systems. Students review how heat and work affect internal energy, why breaking bonds absorbs energy, and why bond formation releases it. They then connect entropy and energy dispersal to the Gibbs free energy equation, ΔG = ΔH − TΔS, using temperature in kelvin.

The concepts continue into equilibrium and energy transfer. Students examine how the sign of ΔG indicates the thermodynamic direction favoured under given conditions, how the standard free energy relationship ΔG° = −RT ln K connects Gibbs free energy with the equilibrium constant, and why a reaction with an unfavourable ΔG can proceed when coupled to a sufficiently favourable reaction. Combustion and electrochemical cells provide examples of chemical energy being transferred as heat, work or electrical work.

🧪 What students practise

Students apply the ideas through multiple-choice questions, true-or-false statements, short-answer calculations and explanations, a labelled diagram, a categorising activity and a short note. The numerical problems include calculating internal energy changes from heat and work, estimating enthalpy from bond energies, and finding Gibbs free energy at a specified temperature. Other tasks ask students to interpret equilibrium conditions, relate the value of K to product or reactant favourability, and calculate the combined ΔG of coupled reactions.

This combination gives students opportunities to move between equations, chemical examples and written scientific reasoning. They must consider how the signs and sizes of ΔH and ΔS influence spontaneity, why temperature can change a reaction's thermodynamic favourability, and how energy transfers operate in combustion and electrochemical systems.

📘 Included with the worksheet

• Printable Grade 12 Science worksheet covering thermodynamics, Gibbs free energy and reaction spontaneity.
• Separate PDF answer key for checking student responses.
• Student Notes lines at the bottom of the worksheet.
• Teacher Guide inside the Answer Key PDF, with Learning Objectives, Teaching Tips, Discussion Questions and Common Mistakes.

🏫 Classroom use

Use this thermodynamics practice resource after introducing the laws of thermodynamics and Gibbs free energy, or as a structured review before an assessment. The calculation questions provide focused practice with the equations, while the explanation tasks help reveal whether students can interpret what their results mean for a chemical reaction. The answer key supports checking and review, and the included Teacher Guide provides prompts for discussion and highlights common areas of difficulty.

Written for Grade 12 Science within the TEKS framework, this resource addresses the supplied standard code SCI.12.7. It brings together the calculations and connected concepts students need to reason about chemical energy, equilibrium and reaction spontaneity in one classroom-ready worksheet.