Thermal Properties of Matter - Quick Revision
Temperature and heat
- Heat is energy transferred due to a temperature difference; temperature measures hotness (SI: kelvin).
- Scales: C/100 = (F-32)/180 = (K-273.15)/100. Ideal-gas/Kelvin scale is absolute.
Thermal expansion
- Linear dL = alpha L dT; area and volume coefficients beta = 2 alpha, gamma = 3 alpha (isotropic solid).
- Anomalous expansion of water: maximum density at 4 C; ice floats and ponds freeze top-down.
Calorimetry
- Q = m c dT (specific heat c); molar specific heat uses moles.
- Latent heat Q = m L (fusion, vaporisation) at constant temperature during a phase change.
- Principle of calorimetry: heat lost = heat gained.
Heat transfer
- Conduction (solids): H = K A (T1-T2)/L, K = thermal conductivity.
- Convection (fluids): bulk movement; natural and forced.
- Radiation: no medium needed. Stefan-Boltzmann H = e sigma A T^4; Wien lambda_m T = b.
- Newton's law of cooling: rate of cooling proportional to excess temperature over surroundings (small differences); used in calorimetry corrections.
Blackbody
- A perfect absorber/emitter; the basis of Stefan and Wien laws; greenhouse effect from selective absorption.