Overview
This lecture explores the foundational concept of energy, its different forms, the law of conservation of energy, and how these ideas relate to both physics and chemistry, especially in terms of energy transfer and storage.
Forms of Energy
- Not everything is made of chemicals; some things like sound or heat are forms of energy, not matter.
- Everything in the universe is fundamentally energy, including matter itself (mass-energy equivalence).
- Mass contains "locked up" nuclear energy, hard to access without nuclear reactions.
- Objects have thermal energy if their temperature is above absolute zero; atoms and molecules jiggle unless at absolute zero.
- Chemical energy is stored in bonds between atoms within molecules.
Energy in Systems (Trebuchet Example)
- Gravitational potential energy is stored due to an object's position in a gravitational field.
- Potential energy means stored energy due to position or arrangement, not "potential to become" energy.
- Energy is never created or destroyed (First Law of Thermodynamics).
Laws and Principles of Energy
- The law of conservation of energy states that the total energy in the universe is constant.
- Thermodynamics is the study of energy, heat, and work.
Definitions: Energy, Work, and Heat
- Energy is defined as the capacity to do work or produce heat.
- Work, in physics/chemistry, involves a force causing movement; no movement means no work.
- Heat is energy transfer due to temperature difference; objects do not 'contain' heat.
Energy Transfer and Systems
- Energy transfers between a system (the subject of study) and its surroundings.
- Internal energy change (ΔE) of a system equals heat (q) plus work (w): ΔE = q + w.
- ΔE is positive when a system gains energy, negative when it loses energy.
Chemical Energy and Reactions
- Chemical energy in molecular bonds is a type of potential energy.
- Exothermic reactions release energy as heat to surroundings.
- Endothermic reactions absorb energy from surroundings.
Key Terms & Definitions
- Energy — the capacity to do work or produce heat.
- Work (w) — energy transfer when a force moves an object.
- Heat (q) — transfer of energy between systems due to temperature differences.
- Potential Energy — energy due to position or arrangement within a system.
- First Law of Thermodynamics — energy cannot be created or destroyed.
- System — the part of the universe being studied.
- Surroundings — everything outside the system.
- Internal Energy (E) — total kinetic and potential energy within a system.
- Exothermic Reaction — process releasing energy to surroundings.
- Endothermic Reaction — process absorbing energy from surroundings.
Action Items / Next Steps
- Review the definitions of energy, work, and heat.
- Practice identifying systems and surroundings in thermodynamic problems.
- Memorize the equation ΔE = q + w.