5.3+Thermal+Energy+and+Heat

=﻿5.3 Thermal Energy and Heat=

Thermal Energy - sum of potential and kinetic energy possessed by the molecules of an object.

As objects become hotter, kinetic energy increases and particles move faster.

Heat - amount of thermal energy absorbed, released or transferred from one object to another.

Qheat = ΔEthermal


 * Determining Heat and Thermal Energy**

We use temperature measure as an indication of the thermal energy.

Three factors affecting the amount of heat transfer:

Specific heat capacity (c) - amount of heat required to raise the temperature of 1 kilogram of a substance by 1°C (or 1 K)
 * 1) Mass - the greater the mass, the more thermal energy at the same temperature
 * 2) Temperature change - the greater the temperature change, the more heat needed
 * 3) Type of material - different types of materials have the ability to store different amounts of heat

c = quantity of heat / (mass x temperature change)

c = Q / m · ΔT

Units: J / kg · °C or J / kg · K

Q = m · c · ΔT


 * Principle of Heat Exchange**

Whenever two substances at different temperatures are mixed, the amount of heat lost by the hotter substance in cooling is equal to the amount of heat gained by the cooler substance in warming.

- Q lost = Q gained

OR

Q lost = - Q gained

OR

Q lost + Q gained = 0