Heat

ICP Chapter 11

Heat/Temp/Energy

• Heat – flow of thermal energy– Heat flows from the warmer object (higher

energy) to the cooler one (lower energy)

• Temperature – average kinetic energy per molecule from random motion

• Thermal Energy – energy of moving/vibrating molecules – energy related to temperature

Units

• Heat is energy – it can be measured in Joules (like KE, PE, and work), calories, or BTU (British Thermal Units).– 1 calorie = 4.186 joules– 1 BTU = 1055 joules

Conductors, Insulators• Conductor – transfer or move heat energy

• Insulator – Keeps the heat energy inside – keeps it from leaving

Specific Heat

• The temperature increase of an object depends on its mass and the material from which it is made.

• Specific heat is a property of a material telling us how much heat energy is needed to raise the temperature of 1 kg by 1°C.

Specific Heat• Knowing the Specific Heat (or Cp) value tells you how

fast the temperature of something will change as it gains or loses energy.

• Metals will warm up (or cool down) fast• Styrofoam will take a longer time and more energy

to change temperature.

• Many mugs are made from ceramics. Will those have a larger or smaller specific heat than iron?

• Why do pots have plastic handles? • Would you rather stir boiling water with a metal or a wood spoon?

Specific Heat Equation

• E = mCp(T2-T1)• E Heat Energy (J)• M mass (kg)• Cp Specific Heat (J/kgC)

• (T2-T1 ) change in temp (°C)

Heat Transfer

• Conduction

• Thermal Equilibrium

Heat Transfer Types

• Conduction

• Convection

• Thermal Radiation