1. Chem-To-Go Lesson 33 Unit 8 HEATING AND COOLING CURVES You’ll need your practice packet to follow the video!

2.  Phase changes involve a flow of heat that can be measured.  Solid to liquid to gas  Melting & Evaporation  Gas to liquid to solid  Freezing & Condensation HEAT FLOW & PHYSICAL CHANGES

3. Heating Curve of Water Endothermic graph (positive slope)

4. The graph shows heat continually flowing into this sample of water.  Solid = heat in causes particles to increase in speed (ΔTemp)  Melting = heat in causes intermolecular forces to weaken  Liquid = heat in causes particles to increase in speed (ΔTemp)  Boiling = heat in causes intermolecular forces to break  Gas = heat in causes particles to increase in speed (ΔTemp)

5. Two Equations Used to Calculate Heat Flow q = mcΔT q = molΔH You must be able to recognize a change in temp vs. a change in heat content. SUMMARY: Diagonal Lines: show heat causing changes in temperature q = mcΔT Plateaus: Show heat causing changes in heat content that weaken/break intermolecular forces without affecting temperature q = molΔH

6. A 5.0 gram sample of water at -40C is heated to 140C. How much heat is required? Let’s use the constants listed on the front of your practice packet.