•Calorimetry: The process of measuring the amount of heat (thermal) energy either absorbed or given off by matter.
•Measurements are made using an insulated container called a calorimeter.
•It's assumed that Heat lost=Heat gained
•You also need to know the specific heat of a substance:the amount of heat energy needed to raise 1 kilogram of a substance 1 ºC ( or 1 K ).
See table on page 141.
 t |
Q is the change in thermal energy in Joules
m is mass in kilograms
c is specific heat in J/Kg
Æt is the change in the temperature.
Example #1: a 32 g silver spoon cools from 60ºC to 20ºC.How much thermal energy was involved? Use Q=mcÆt and just plug in the numbers.
32g=.032kg, specific heat of silver= 235J/K
Æt (20º - 60º)= -40ºC
.032kg • 235J/K • -40ºC = -301 J ( the negative sign means heat is given off)
Example #2: Calculate heat energy for 2,500 g of sand to go from 19º C to 30º C !
2.5kg•664K/J•11ºC=18,260 J