Theme B · Particulate Nature of Matter

Absolute zero = 0 K; molecular KE $\to$ 0.

Conduction (solids), convection (fluids), radiation (EM waves, works in vacuum).

Temperature stays constant during melting/boiling.

Sum of random KE + PE of particles. For an ideal gas $U \propto T$.

$T$ in kelvin; $R = 8.31$ J mol⁻¹ K⁻¹.

Pressure arises from particle collisions with walls; faster (hotter) ⇒ higher pressure.

Use when p, V and T all change. $T$ MUST be in kelvin.

$k_B = 1.38\times10^{-23}$ J K⁻¹; depends only on T.

Pa = N m⁻². In a liquid: $p=\rho g h$ (depth only).

Floats when upthrust = weight (Archimedes: upthrust = weight of fluid displaced).

Power ∝ $T^4$: double T ⇒ ×16 power.

$T$: K · $Q$: J · $c$: J kg⁻¹ K⁻¹ · $L$: J kg⁻¹ · $p$: Pa · $V$: m³ · $n$: mol · $\rho$: kg m⁻³.

Using °C instead of K in gas laws; forgetting T is constant during a phase change; not converting cm³→m³ or g→kg.