Thermal Physics
Heat, temperature, and why ice cream melts in Karachi summers
Temperature vs Heat:
Heat Transfer Methods:
Conduction: Heat travels through solids by particle vibrations. Metals are good conductors (that's why a metal spoon in hot chai gets hot). Wood and plastic are insulators.
Convection: Heat transfer in fluids (liquids and gases) through movement. Hot fluid rises (less dense), cool fluid sinks. This creates convection currents — like the sea breeze in Karachi.
Radiation: Heat transfer through electromagnetic waves. No medium needed — this is how the sun heats the Earth. Dark surfaces absorb more radiation; shiny surfaces reflect it.
States of Matter:
During state changes, temperature stays constant — all energy goes into breaking/forming bonds between particles.
Specific Heat Capacity: The energy needed to raise 1 kg of a substance by 1°C.
E = mcΔT (Energy = mass × specific heat capacity × temperature change)
Key Points to Remember
- 1Heat transfers by conduction, convection, and radiation
- 2Energy for temperature change: E = mcΔT
- 3During state changes, temperature remains constant
- 4Dark surfaces absorb more radiation; shiny surfaces reflect
Pakistan Example
Karachi Sea Breeze
Karachi's sea breeze is a perfect example of convection. During the day, land heats up faster than the sea. Hot air over the land rises (less dense), and cooler air from the sea rushes in to replace it — that's the refreshing sea breeze! At night, it reverses: land cools faster, sea air rises, and a land breeze blows toward the sea. This is why Karachi evenings near the beach feel so pleasant.