Catalyst: 1. Differentiate between the meaning of the value for q and the meaning for the value of Δ H. 2. Differentiate between the meaning of q and the.

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Presentation transcript:

Catalyst: 1. Differentiate between the meaning of the value for q and the meaning for the value of Δ H. 2. Differentiate between the meaning of q and the meaning of temperature.

 Up to this point we have talked about Δ H and q in theoretical terms.  How do we go into the lab and measure these quantities?  The measurement of heat flow is the science of calorimetry. Heat flow is measured with a calorimeter.

 The amount of of heat it takes to change the temperature is dependent on the substance being studied.  The heat capacity is the amount of energy required to raise a substances temperature 1 o C.  The specific heat (C s ) describes the amount of energy that is required to change one gram of a substance, one degree C.

 Therefore, if specific heat is known (it is a constant), then heat can be calculated:  For a phase change, heat can be calculated by:

 When doing multiple steps for a single heating, think of the heating curve.  Each portion of the line represents a different q term  Can solve for q total by adding up q terms for a problem.  Make sure to include the q of the calorimeter. Time (s) Heat Added (J) a b c d e q total = q a + q b + q c + q d + q e

 How much energy is needed to change 150 g of solid ice from 0 o C to 50 o C? The specific heat of liquid water is J/(g x o C) and the Δ H fusion = 6.0 kJ/mol

 How much heat is required to convert a 120 g snowman from –10.0 C to 108 C? Note the following terms:  Δ H fusion = 6.0 kJ/mol C s, solid = 2.1 J/(g x o C)  Δ H condensation = kJ/mol C s, liquid = J/(g x o C) C s, gas = 1.7 J/(g x o C)

Rate yourself 1 – 4 on All Unit 0 and 1 LTs

 Complete Problem Set 1.1, 1.2, and 1.3, and 1.6  Be sure to use the appropriate units!

 Upload all of your lab work to your wikispaces page under the correct tab.  Unit 0-1 Assessment Mon/Tuesday  Keep looking at your new and improved learning logs to guide your studying!  Review Class on Thurs/Fri!