Test #3 Phase Changes

How much heat energy does it take to warm, melt, or boil a substance? ~~ Calorimetry ~~ q = m c  T q = m H f q = m H v q = heat in joules m = mass in grams c = specific heat capacity Heat of fusion = H f Heat of vaporization = H v  T = change in temp

And, how does the temperature change?

Heating Curves This graph shows how the temperature of a substance changes over time as the substance is heated at a uniform rate, starting as a solid. Neatly draw a BIG Sketch of this diagram in your notes!

Label Phases SOLID LIQUID GAS

Label Phase Changes MELTING BOILING

NBP & NMP at 1 atm Melting Point / Freezing Point (For water 0 o C) Boiling Point/ Condensation Point (For water 100 o C)

Heat of Fusion & Heat of Vaporization Heat of Fusion = amount of heat needed to change S  L at its melting point H f = 334 J/g for water Heat of Vaporization = amount of heat needed to change L  G at its boiling point H v = 2260 J/g for water Why is DE longer than BC?

Kinetic Energy & Potential Energy AB = The Solid’s Temperature & Kinetic Energy increase BC = Melting ( Temp & KE are constant, but PE increases as S  L) CD = The Liquid’s Temp & KE increase DE = Boiling ( Temp & KE are constant, but PE increases as L  G) EF = The Gas’s Temp & KE increase

Note! 1. Temperature doesn’t change during phase changes (BC & DE = the flat parts) 2. During Phase Changes: Heat Energy  Potential Energy (Solids have the least PE, Gases the most PE) 3.During Temp Changes: Heat Energy  Kinetic Energy (AB, CD, EF = the diagonals)

HeatingCurve.htm HeatingCurve.htm