Specific Heat Enthalpy Calculations in thermochemistry Specific Heat

Specific Heat & Enthalpy Calculations in thermochemistry

Specific Heat & Enthalpy �What’s specific heat anyway? The amount of energy required to raise the temperature of 1 g of a substance 1°C or 1 K degree. �DEFINITION: �Values (units) of specific heat are in J/g(°C) OR J/g(K) OR Cal/g(°C)

Specific Heat & Enthalpy FORMULA PLEASE ; -) Q=m. C� T �Q=heat applied (in Cal or J) (BTW: 4. 18 J = 1 cal) �m=mass in GRAMS �C=specific heat �� T= CHANGE in temperature (make sure it’s in the correct unit—NO °F!!!)

Specific Heat & Enthalpy �TEMPERATURE? �Temperature is a measure of the average KE of the particles in a sample of matter. �HEAT? �The energy transferred between samples of matter because of differences in temp. �Heat is a form of energy and is measured by the SI unit JOULE. A Joule is derived from the units of force and length N x m= kg x m 2 s 2

Specific Heat & Enthalpy J=Joule KJ=Kilojoule 1000 J = 1 KJ � H? ��means “change”, H means heat, therefore �H means “change in heat”. It can be positive (+) or negative (-). �Heat moves from HIGH to LOW temperature.

Specific Heat & Enthalpy �H = Hproducts - Hreactants Keep in mind that chem equations are written as REACTANTS �PRODUCTS + �H means that heat was absorbed, the reaction is endothermic (products are colder) - �H means that heat was released, the reaction is exothermic (products are warmer)