1. U3 S1 L3 Constant Pressure Calorimetry. Textbook Readings MHR pages 661-664: The Technology of Heat Measurement Textbook Practice Items MHR pages 664-665: items 1, 2, 3, and 4 Homework Postings: last page.

2. Upon completion of this lesson, you should be able to: define the calorimeter and identify it as the basic instrument for measuring heat transfer calculate the heat gained by or lost from a system using the formulas q=mc∆T and/or q = c∆T

3. Calorimetry Calorimetry is the measurement of heat changes. –It is carried out using devices called calorimeters. Calorimetry is based on the idea that energy lost by a system equals the energy gained by the surroundings and vice versa; in other words, it is based on the first law of thermodynamics. q sys = - q surr There are two basic types of calorimeter: 1.constant pressure (or simple calorimeter or coffee-cup calorimeter) The water in the calorimeter is the surroundings q sys = - q water 2.constant volume or bomb calorimeter. the calorimeter is the surroundings, q sys = - q calorimeter

4. Constant Pressure Calorimeter (simple calorimeter)

5. Bomb Calorimeter

6. The simple calorimeter consists of an insulated container, a thermometer, and a known amount of water (see Figure 17.1 on p.661 of MHR). It is used to measure heat changes associated with heating, cooling, phase changes, solution formation, and chemical reactions that occur in aqueous solution. you will assume that when an energy change occurs in a simple calorimeter, the calorimeter water absorbs or releases all of the energy associated with the change. In other words, the calorimeter (specifically the calorimeter water) takes on the role of the surroundings. C water =4.19 J/gC The final temperature of the system and surroundings will be the same. T f is the same for the system and the surrounding.

7. 1.A very cold piece of silver with a mass of 78.41 g is added to a simple calorimeter that contains 150.0 g of water. The temperature of the calorimeter water changes from 19.73°C to 16.11°C. (The specific heat capacity of silver is 0.24 J/g°C.) a.Calculate the heat change for the piece of silver. b.How cold was the piece of silver?

8. 2.A simple calorimeter with a heat capacity of 1.05 kJ/°C undergoes a decrease of 1.56°C when a very cold piece of iron is added to it. Calculate the heat change of the iron

9. 3.A simple calorimeter contains 150.0 g of water. A 5.20 g piece of an alloy at 525.0°C is dropped into the calorimeter causing the temperature of the calorimeter water to increase from 19.30°C to 22.68°C. Calculate the specific heat capacity of the alloy.

10. 4.The temperature in simple calorimeter with a heat capacity of 1.05 kJ/°C changes from 25.0°C to 23.94°C when a very cold 12.8 g piece of copper was added to it. Calculate the initial temperature of the piece of copper.

11. 5.A new ceramic material underwent for use as an insulator. Part of the analysis involved determining its specific heat capacity. A 20.00 g sample was heated to 200.0°C and added to a simple calorimeter with a heat capacity of 1.46 kJ/°C. The temperature in the calorimeter changed from 24.87°C to 27.15°C. Calculate the specific heat of the ceramic material.

12. 6.A new composite material used in airplane construction was being analyzed in order to prepare a detail list of its physical properties. Describe the procedure you would use to determine its specific heat capacity.

13. Homework – postings u3s1L3: 1. Gold has a specific heat capacity of 0.129 J/g.C (a) How much heat will a piece of gold having a mass of 5.00 g transfer when it changes temperature by 50.0 o C? (ans:32.3) (b) If this 5.00 g piece of gold is placed into 10.0 g of water, what temperature change will occur in the water for the 50.0 o C change in the gold?(ans: 0.77 o C) 2. A calorimeter designed to have negligible heat loss is used to determine the specific heat capacity of metals. A piece of thallium having a mass of 111.2 g is warmed to 95.0ºC and placed into the calorimeter containing 125.00 g of water at 12.5ºC. The water temperature goes up to 14.9ºC. Use this information to calculate the specific heat capacity of thallium. The specific heat capacity of water is 4.184 J/g·ºC. (ans:0.14 j/g.C)