Slide 1Slide 2Energy TransformationsSlide 4Exothermic and Endothermic ProcessesSlide 6Slide 7Slide 8Units for Measuring Heat FlowSlide 10Slide 11Slide 12Slide 13CalorimetryA foam cup calorimeter – here, two cups are nestled together for better insulationSlide 16Slide 17Laboratory 12CALORIMETRYObjectives1. Construct and utilize a coffee cup calorimeter to measure heat changes2. Determine the heat capacity of a calorimeter3. Determine the specific heat of an unknown metal sampleEnergy Transformations•“Thermochemistry” - concerned with heat changes that occur during chemical reactions•Energy - capacity for doing work or supplying heat–weightless, odorless, tasteless–if within the chemical substances- called chemical potential energyEnergy Transformations•Heat - represented by “q”, is energy that transfers from one object to another, because of a temperature difference between them.–only changes can be detected!–flows from warmer  cooler objectExothermic and Endothermic Processes• Essentially all chemical reactions and changes in physical state involve either:a) release of heat, orb) absorption of heatExothermic and Endothermic Processes•In studying heat changes, think of defining these two parts:–the system - the part of the universe on which you focus your attention–the surroundings - includes everything else in the universe•Heat flowing into a system from it’s surroundings:–defined as positive–q has a positive value–called endothermic•system gains heat (gets warmer) as the surroundings cool down•Heat flowing out of a system into it’s surroundings:–defined as negative–q has a negative value–called exothermic•system loses heat (gets cooler) as the surroundings heat upUnits for Measuring Heat Flow1) A calorie is defined as the quantity of heat needed to raise the temperature of 1 g of pure water by 1 oC.2) The calorie is also related to the Joule, the SI unit of heat and energy–named after James Prescott Joule–4.184 J = 1 cal•Heat Capacity - the amount of heat needed to increase the temperature of an object exactly by 1 oC–Depends on both the object’s mass and its chemical compositionSpecific Heat Capacity (abbreviated “C”) The amount of heat it takes to raise the temperature of 1 gram of the substance by 1 oC.often called simply “Specific Heat”Note the tremendous difference in Specific Heat.Water’s value is VERY HIGH. Thus, for water:it takes a long time to heat up, and it takes a long time to cool off!Heat Capacity and Specific HeatTo calculate, use the formula: q = mass (in grams) x T x Cheat is abbreviated as “q”T = change in temperatureC = Specific HeatUnits are either: J/(g oC) or cal/(g oC)Calorimetry•Calorimetry - the measurement of the heat into or out of a system for chemical and physical processes.heat released = heat absorbed•The device used to measure the absorption or release of heat in chemical or physical processes is called a “Calorimeter”A foam cup calorimeter – here, two cups are nestled together for better insulationCalorimetry•Changes in enthalpy = H•q = H •Thus, q = H = m x C x TH is negative for an exothermic reactionH is positive for an endothermic reactionAssigned Reflection Questions Questions 1,2,3 and