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Expansion problems: Always use $\Delta L = L_0\alpha\Delta T$. Remember holes expand. For density: $\rho = \rho_0/(1+\gamma\Delta T)$. For pendulum clocks: $\Delta T_{\text{period}}/T = (1/2)\alpha\Delta T_{\text{temp}}$.

Calorimetry problems: Work in a single unit system (CGS with calories is often simplest). Step-by-step approach for phase changes. Always check if the calculated $T_f$ is physically possible (0 to 100 degrees C for water at 1 atm).

Conduction problems: Draw the thermal circuit. Identify series/parallel. Calculate resistances: $R = L/(kA)$. Apply $dQ/dt = \Delta T/R_{\text{total}}$. For junction temperatures: $T_j = T_{\text{hot}} - (dQ/dt) \times R_{\text{up to junction}}$.

Radiation problems: Always convert to Kelvin. $P \propto T^4$ for total radiation. Wien's law for peak wavelength. Newton's cooling for small temperature excess — use the average form and set up two equations to find $k$ and $T_s$.

Common traps: (1) Using Celsius instead of Kelvin in Stefan's law. (2) Forgetting latent heat in mixing problems. (3) Confusing series and parallel conduction. (4) Assuming Newton's law works for large temperature differences. (5) Forgetting to include calorimeter's water equivalent.