The Particulate Nature of Matter
1. Kinetic Particle Theory
-
๐น Description of States:
-
๐น Solids:
Particles are closely packed in a fixed lattice, vibrating in place; strong intermolecular forces; definite shape and volume.
-
๐น Liquids:
Particles are close but mobile, sliding past each other; weaker forces than solids; definite volume, no fixed shape.
-
๐น Gases:
Particles are far apart, moving rapidly and randomly; very weak forces; no fixed shape or volume.
-
๐น Solids:
-
๐น Interconversion:
- ๐น Melting: Solid โ Liquid
- ๐น Boiling/Evaporation: Liquid โ Gas
- ๐น Freezing: Liquid โ Solid
- ๐น Condensation: Gas โ Liquid
- ๐น Sublimation: Solid โ Gas (e.g., dry ice)
-
๐น Evidence for Particle Movement:
-
๐น Diffusion:
Random movement of particles from high to low concentration.
-
๐น In Liquids:
Potassium permanganate (KMnOโ) spreads slowly in water.
-
๐น In Gases:
Bromine gas spreads in a sealed container.
-
๐น Diffusion:
-
๐น Everyday Effects:
- ๐น Spread of perfume or cooking aromas through air.
- ๐น Mixing of gases, e.g., car exhaust dispersing in atmosphere.
-
๐น Effect on Diffusion:
-
๐น Molecular Mass:
Lighter particles diffuse faster (Grahamโs Law: rate โ 1/โmolar mass). Example: NHโ (17 g/mol) diffuses faster than HCl (36.5 g/mol).
-
๐น Temperature:
Higher temperature increases particle kinetic energy, speeding up diffusion.
-
๐น Molecular Mass:
2. Atomic Structure
-
๐น Relative Charges and Masses:
-
๐น Proton:
Charge +1, mass 1 u
-
๐น Neutron:
Charge 0, mass 1 u
-
๐น Electron:
Charge -1, mass ~1/1836 u (negligible)
-
๐น Proton:
-
๐น Structure of Atom:
Nucleus (protons + neutrons) at center with most mass; electrons orbit in shells around nucleus.
-
๐น Proton and Nucleon Numbers:
-
๐น Proton Number (Z):
Number of protons; defines the element.
-
๐น Nucleon Number (A):
Sum of protons and neutrons.
-
๐น Example:
Carbon-12: ยนยฒโC (6 protons, 6 neutrons)
-
๐น Proton Number (Z):
-
๐น Nuclide Notation:
Written as แดฌ๐ฉX , where A = nucleon number, Z = proton number, X = element symbol.
-
๐น Isotopes:
Atoms with same proton number but different neutron numbers. Example: ยนยฒโC and ยนโดโC.
-
๐น Deduction of Numbers:
-
๐น Neutral Atoms:
Protons = Electrons = Z; Neutrons = A - Z. Example: ยนโถโO โ 8 protons, 8 electrons, 8 neutrons.
-
๐น Ions:
Electron count adjusted by charge. Example: Oยฒโป from ยนโถโO โ 8 protons, 10 electrons, 8 neutrons.
-
๐น Neutral Atoms:
- โ ๏ธ Particles in solids do not move; actually, they vibrate in fixed positions.
- โ ๏ธ Diffusion rates are the same for all substances; lighter molecules and higher temperatures increase rates.
- โ ๏ธ Proton number is the same as nucleon number; proton number defines element, nucleon number includes neutrons.
- โ ๏ธ Isotopes have different chemical properties; they differ mainly in physical properties like mass.
- ๐ Describe particle arrangement and movement in solids, liquids, and gases, including state changes.
- ๐ Explain diffusion experiments and relate to molecular mass and temperature.
- ๐ Practice calculating proton, neutron, and electron numbers using nuclide notation.
- ๐ Memorize charges and masses of subatomic particles.
- ๐ Distinguish isotopes by neutron count, not chemical behavior.