thermochemistry
Here are clean, organized study notes based on all the thermochemistry, kinetics, and equilibrium worksheets you uploaded. I condensed everything into a structured, easy‑to‑study format.
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🔥 THERMOCHEMISTRY NOTES
1. Thermochemistry Basics
• Thermochemistry = study of heat energy absorbed or released in chemical reactions or phase changes.
• System = part being studied (e.g., a hand warmer).
• Surroundings = everything else.
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2. Energy
Types of Energy
Potential Energy
• Energy of position.
• Stored in chemical bonds.
• Determined by type and number of bonds.
Kinetic Energy
• Energy of motion.
• Formed when chemical bonds break.
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3. Law of Conservation of Energy
• Energy is never created or destroyed, only changes form.
• Energy often lost as heat (e.g., car engines lose most energy as heat).
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4. Heat vs. Temperature
• Heat: energy that flows from warmer → cooler objects.
• Temperature: measure of hotness/coldness, not total energy.
• Scales: Fahrenheit, Celsius (based on water), Kelvin (SI, starts at absolute zero).
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5. Measuring Heat
• Joule (J) = SI unit of heat & energy.
• Calorie = heat needed to raise 1 g of water by 1°C.
• Food Calorie = 1 kilocalorie = 1000 calories.
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🔥 SPECIFIC HEAT & CALORIMETRY
6. Specific Heat Capacity
• Amount of heat needed to raise 1 g of a substance by 1°C.
• Each substance has its own value due to different atomic arrangements.
Common Specific Heats (J/g°C):
• Water: 4.18
• Aluminum: 0.897
• Gold: 0.129
• Ethanol: 2.44
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7. Calorimetry
• Measures heat absorbed or released.
• Uses a calorimeter (often styrofoam cup).
• Must know:• Mass
• Temperature change
• Specific heat
Specific Heat Equation
q = m c \Delta T
• \( q \) = heat (J)
• \( m \) = mass
• \( c \) = specific heat
• \( \Delta T = T_f - T_i \)
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🔥 ENTHALPY (ΔH)
8. Enthalpy Basics
• Enthalpy = heat content of a system at constant pressure.
• Only changes in enthalpy can be measured.
• ΔH = \( H_{\text{products}} - H_{\text{reactants}} \)
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9. Exothermic vs. Endothermic
Exothermic
• Energy released.
• Heat flows to surroundings.
• ΔH is negative.
• Reactants lose heat.
• Container feels hot.
• Graph: energy drops from reactants → products.
Endothermic
• Energy absorbed.
• Heat flows from surroundings.
• ΔH is positive.
• Reactants gain heat.
• Container feels cold.
• Graph: energy rises from reactants → products.
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🔥 PHASE CHANGES
Phase Change Enthalpy
• Freezing: liquid → solid, loses energy, –ΔH
• Melting: solid → liquid, gains energy, +ΔH
• Boiling/Vaporizing: liquid → gas, gains energy, +ΔH
• Condensing: gas → liquid, loses energy, –ΔH
Heating Curve of Water
• A–B: solid heating (temp ↑)
• B–C: melting (temp constant)
• C–D: liquid heating (temp ↑)
• D–E: boiling (temp constant)
• E–F: gas heating (temp ↑)
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🔥 HESS’S LAW
• If multiple reactions add up to a final reaction, their ΔH values also add.
• You may need to:• Reverse equations (change sign of ΔH)
• Multiply/divide equations (do same to ΔH)
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⚡ KINETICS & COLLISION THEORY
10. Reaction Rates
• Rate = change in concentration over time.
• Units: M/s or mol/L/s.
11. Collision Theory
A reaction occurs only if:
1. Particles collide.
2. They collide with enough energy.
3. They collide with correct orientation.
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12. Activation Energy (Ea)
• Minimum energy needed to form the activated complex.
• If particles reach Ea → products form.
• If not → revert to reactants.
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13. Factors Affecting Reaction Rate
Nature of Reactants
• Some elements react faster (e.g., groups 1A & 2A).
• Reactivity increases down a family.
Concentration
• Higher concentration → more collisions → faster rate.
Surface Area
• More surface area → more collision sites → faster rate.
Temperature
• Higher temperature → more kinetic energy → more collisions → faster rate.
Catalysts
• Lower activation energy.
• Speed up reaction without being consumed.
• Do not change amount of product.
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⚖ CHEMICAL EQUILIBRIUM & LE CHATELIER’S PRINCIPLE
14. Reaction Completion
• Reactants decrease, products increase.
• Most reactions are reversible (⇌).
15. Chemical Equilibrium
• Forward and reverse reaction rates become equal.
• Concentrations stay constant, not equal.
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16. Le Chatelier’s Principle
A system shifts to relieve stress.
Changes in Concentration
• Add reactants → shift right
• Remove reactants → shift left
• Add products → shift left
• Remove products → shift right
Changes in Temperature
Exothermic (heat = product):
• Increase temp → shift left
• Decrease temp → shift right
Endothermic (heat = reactant):
• Increase temp → shift right
• Decrease temp → shift left
Changes in Pressure (gases only)
• Increase pressure → shift to side with fewer gas molecules
• Decrease pressure → shift to side with more gas molecules
• If equal gas moles → no effect
Catalysts
• Reach equilibrium faster, but no shift.
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