Chemistry is the central science that bridges physics and biology, exploring the composition, structure, properties, and transformations of matter. Here’s a concise breakdown of core chemistry concepts, with connections to packaging chemistry:

1. Atomic Structure & Bonding Atoms: Basic units of matter (protons, neutrons, electrons). Chemical Bonds: Covalent Bonds: Shared electrons (e.g., C-C bonds in plastics like PET). Ionic Bonds: Electron transfer (e.g., NaCl in glass coatings). Hydrogen Bonds: Weak interactions (critical for paper’s water absorption). Why it matters for packaging: Bond strength determines material durability (e.g., covalent bonds in polymers resist degradation).
2. Molecules & Compounds Molecules: Groups of atoms bonded together (e.g., H?O, O?). Compounds: Pure substances of two+ elements (e.g., SiO? in glass, C?H? in polyethylene). Why it matters: Packaging materials (plastics, glass, metals) are compounds/molecules engineered for specific properties.
3. Chemical Reactions Types: Synthesis: Combining reactants (e.g., polymerization: ethylene ? polyethylene). Decomposition: Breaking down (e.g., UV degradation of plastics). Oxidation: Loss of electrons (e.g., metal corrosion in cans). Why it matters: Reactions cause material degradation (e.g., hydrolysis of PLA in compost) or enable recycling (e.g., depolymerization).
4. States of Matter Solid, Liquid, Gas: Solids: Rigid structure (glass, metals). Liquids: Flow (inks, coatings). Gases: Permeate barriers (O?, CO?). Why it matters: Packaging must control gas/liquid movement (e.g., EVOH layers block O? gas).
5. Solutions & Solubility "Like dissolves like": Polar solvents dissolve polar solutes (e.g., water in paper). Why it matters: Migration of additives (e.g., plasticizers leaching into fatty foods). Scalping (flavors absorbed by packaging).
6. Acids & Bases (pH) pH Scale: Measures acidity/alkalinity (0–14). Why it matters: Acidic foods corrode metal cans. pH-sensitive coatings (e.g., epoxy in cans) prevent reactions.
7. Thermodynamics Energy Changes: Exothermic: Releases energy (combustion). Endothermic: Absorbs energy (melting). Why it matters: Heat sealing (exothermic bonding) or cold storage stability.
8. Kinetics & Equilibrium Reaction Rates: Speed of reactions (e.g., antioxidant additives slow oxidation). Equilibrium: Balance between forward/reverse reactions (e.g., moisture permeation). Why it matters: Shelf-life prediction (e.g., how fast O? degrades food).
9. Polymers Macromolecules: Long chains of repeating units (monomers). Addition Polymers: Polyethylene, PP. Condensation Polymers: PET, nylon. Why it matters: 90% of flexible packaging relies on polymers. Properties (flexibility, barrier) depend on chain length/branching.
10. Intermolecular Forces (IMFs) Forces between molecules: London Dispersion: Weak (e.g., polyethylene’s flexibility). Dipole-Dipole: Stronger (e.g., PVC’s rigidity). Hydrogen Bonding: Strongest (e.g., paper’s strength). Why it matters: IMFs control barrier properties (e.g., strong IMFs in EVOH block O?).
11. Electrochemistry Redox Reactions: Transfer of electrons (e.g., metal corrosion: Fe ? Fe²? + 2e?). Why it matters: Corrosion prevention in metal cans (e.g., tin coatings).
12. Nuclear Chemistry Radioactivity: Unstable nuclei emit radiation. Why it matters: Radiation sterilization of medical packaging (e.g., gamma rays).