Chemistry Unit 5

Calorimetry

When ionic compounds dissolve in water, it is generally considered a physical change. The ionic bonds between the ions in the compound are broken, allowing the ions to disperse in the solution, but the compound itself remains intact at a molecular level and can typically be recovered through evaporation of the solvent.

Heat vs Temperature

Heat

• exchange of thermal energy between samples of matter

• heat flows from high temperature zones to low temperature zones until they reach thermal equilibrium (same average kinetic energy in the molecules)

• heat is exchanged through molecular collisions between particles

Temperature

• measure of thermal energy (average kinetic energy) of molecules in a sample

• NOT ALL THE MOLECULES IN A SAMPLE HAVE THE SAME KINETIC ENERGY (there is variation but the average is temperature)

The amount the temperature of an object increases depends on its mass • If you double the mass it will take twice as much heat energy to raise the temperature the same amount.