flask Thermochemistry & Thermodynamics
Thermochemistry answers why some reactions release heat and others absorb it, and whether a reaction can happen on its own. These ideas power everything from calorimetry labs to batteries to climate science.
What you will learn
- Distinguish heat and temperature
- Calculate heat transfer with calorimetry
- Use enthalpy and Hess's law
- Apply entropy and Gibbs free energy
- Predict reaction spontaneity
Introductory College concepts
Bond Enthalpies: Estimating ΔH from Chemical Bonds
Breaking bonds costs energy; forming bonds releases it. Estimate a reaction's enthalpy change from average bond enthalpies with one simple subtraction.
Standard Enthalpies of Formation and How to Use Them
Every compound has a ΔH°f: the enthalpy change of forming one mole from its elements. Learn to use formation data to compute any reaction's ΔH°.
Entropy: Why the Universe Loves Disorder
Entropy measures how spread out energy and matter are. Learn why systems drift toward disorder and what that means for chemical reactions.
Gibbs Free Energy: The Equation That Decides
ΔG = ΔH − TΔS packs enthalpy, entropy, and temperature into one number. Negative ΔG means the process can happen on its own.
Hess's Law: Bookkeeping for Reaction Enthalpies
Hess's law says the total enthalpy change is the same no matter the path. Add, flip, and scale reaction steps to find ΔH for hard-to-measure reactions.
Predicting Spontaneity: The Four Cases of ΔH and ΔS
Four sign combinations of ΔH and ΔS decide whether a reaction runs on its own. Learn the table and find the temperature where the verdict flips.
High School concepts
Calorimetry: How Chemists Measure Heat Flow
Calorimeters trap a reaction's heat in water and convert a temperature change into joules with q = mcΔT. See how coffee-cup calorimeters work.
Enthalpy: The Heat Content of a Chemical System
Enthalpy (H) is the total heat content of a system at constant pressure. Learn what ΔH means, how signs work, and why chemists love this state function.
Specific Heat Capacity: Why Water Resists Change
Specific heat capacity is the energy needed to warm one gram by one degree. Water's 4.184 J/(g·°C) — set by hydrogen bonds — steadies Earth's climate.
Beginner concepts
Endothermic and Exothermic Processes Explained
Endothermic processes absorb heat from the surroundings; exothermic processes release it. Learn to read energy diagrams and predict temperature changes.
Heat vs Temperature: What's the Real Difference?
Temperature measures average particle motion; heat is thermal energy moving from a hotter object to a cooler one. Learn to tell them apart.
Formulas
Calorimetry: Heat Lost = Heat Gained
q_lost = -q_gained (heat lost by hot = heat gained by cold)
Standard Enthalpy of Reaction
ΔH°rxn = ΣnΔH°f(products) − ΣmΔH°f(reactants)
Entropy Change
ΔS = q_rev/T ; ΔS°rxn = ΣnS°(products) − ΣmS°(reactants)
Gibbs Free Energy
ΔG = ΔH − TΔS ; ΔG° = −RT ln K
Specific Heat Equation (q = mcΔT)
q = mcΔT
Hess's Law of Heat Summation
ΔH°rxn = Σ ΔH°(steps) — overall enthalpy = sum of step enthalpies