http://www.youtube.com/watch?v=ZroSAGUlzGs

Activities In your groups perform the outlined activities for five (5) minutes and answer the questions Discuss the reasons for any temperature change and any differences between the value for the two materials for five (5) minutes (take into consideration what factor you are changing) Present your group’s analysis (three minutes per group)

Heat Capacity Based on the Kinetic theory of matter: The heat capacity, C of a material is the quantity of energy required to raise the temperature of a body by 1K. The units for heat capacity are J/K or JK-1 i.e. C = EH/ΔT, EH = CΔT where EH is the amount of energy required and ΔT is the temperature difference

Example 10000J of energy was required to increase a material from room temperature of 308K to 328K. What is the heat capacity of the material?

Calculation C = EH/ΔT Step 1: EH = 10000J Step 2: ΔT = 328 – 308 = 20K Step 3: C = 10000 / 20 C = 500 J/K

Specific Heat Capacity Specific heat capacity, c is defined as the quantity of heat which is needed to raise the temperature of 1 kg of a body by 1K or 1 °C The unit for specific heat capacity is Jkg-1 K-1 The relationship to heat capacity is: C = mc

C = mc = EH/ΔT EH = mcΔT So if in the above example the mass of the body is 0.5 kg then the specific heat capacity is :

C = mc Step 1: m = 0.5kg Step 2: C = 500J/K Step 3: 500 = 0.5 x c c = 500/0.5 = 1000 Jkg-1 K-1

What does this mean? Consider the specific heat of copper , 0.385 J/g 0C. This means is that it takes 0.385 Joules of heat to raise 1 gram of copper 1 degree Celsius. Thus, if we take 1 gram of copper at 25 0C and add 1 Joule of heat to it, we will find that the temperature of the copper will have risen to 26 0C. We can then ask: How much heat will it take to raise by 1 0C 2g of copper?. 0.385 J for each gram or 2x0.385 J = 0.770 J. What about a pound of copper?

Example 50000 J of energy was required to raise the temperature of 500g of a liquid from 31°Cto 56°C. What is the specific heat capacity of the liquid?

Calculation EH = mcΔT Step 1: m= 500g = 0.5Kg Step 2: ΔT = 56-31 °C = 25°C EH = 50000J 50000 = 0.5 x c x 25 c = 50000/(0.5 x 25) c= 4000 Jkg-1 K-1

How can I apply this knowledge? Substance J/kg/oC or J/kg/K Water (0 oC to 100 oC) 4186 Methyl Alcohol 2549 Ice (-10 oC to 0 oC) 2093 Steam (100 oC) 2009 Wood (typical) 1674 Soil (typical) 1046 Air (50 oC) Aluminum 900 Marble 858 Glass (typical) 837 Iron/Steel 452 Copper 387 Silver 236 Mercury 138 Gold 130 Lead 128 Oil, vegetable 1670 Oil, Olive 1970 Petroleum 2130

Where would you use these materials Where would you use these materials? And when would you need to have heat applied?

Summary Heat capacity and Specific Heat capacity are not the same Heat capacity is the amount of heat required to raise the temperature of a body by 1K Specific heat capacity, c is defined as the quantity of heat which is needed to raise the temperature of 1 kg of a body by 1K or 1 °C Specific heat capacity includes the mass of the material

Assessment 1) Define heat capacity: Heat capacity is _____________________________________________________________________________________________________ 2) Define specific heat capacity: Specific heat capacity is ______________________________________________________________________________________________________ 3) What is the major difference between Heat capacity and specific heat capacity? _______________________________________________________________________________________________________ _____________________________________________________________ 4) 0.1 kg masses of aluminium and copper (Cu) initially at 30°C absorb the same amount of heat at the same rate for the same length of time. What is the specific heat capacity of aluminium if the temperatures of the aluminium mass after heating is 50°C and that of copper is 75°C. Specific heat capacity of Copper = 400 Jkg-1 K-1 J Mass of Copper = ____________kg Mass of Aluminium = __________kg Initial temperature of Copper = _________°C Initial temperature of Aluminium = _________°C Final temperature of Copper = _________°C Final temperature of Aluminium = _________°C Temperature change for copper ΔT = _________°C Temperature change for Aluminium ΔT = _________°C Temperature change for copper ΔT = _________K Temperature change for Aluminium ΔT = _________K EH = EH = ? 5) Write below why do you think it is important to know specific information on the heat capacity and specific heat capacity of materials. (Relate heat capacity and specific heat capacity to situations you may deem important) ____________________________________________________________________________________________________________________________________________________________________________________________________

Bonus In a factory that makes PVC pipes, the process that involves the chemical changes of the reactants to the product releases a lot of heat energy. The material that make up the machine has a high specific heat capacity or a low one? A worker was sent to clean the machine and puts a coat of paint on the machine with a low specific heat capacity, what problems do you think may occur?

Home work Explain your answer. A heater is used to measure the temperature of each of four metal blocks A, B, C and D in turn. The blocks have equal volumes and the heater is switched on for the same length of time in each case. Which block would have the smallest temperature change: Explain your answer. Block Mass/kg Specific Heat Capacity/Jkg-1 K-1 A 0.9 100 B 0.8 500 C 0.7 400 D 0.2 900