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Unit 1 ENERGY 1.3 How do you calculate heat at melting and vaporization? March 24, 2010 Objective 1: SWBAT calculate the amount of heat required to change the temperature of a substance. DO NOW: 1.What do the following segments represent? BC CD DE AB Melting FUSION Liquid phase Boiling VAPORIZATION Solid phase

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HEAT OF FUSION The amount of heat needed to convert a unit mass of a substance from solid to liquid is called the heat of fusion. The equation used is q = mH f.

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EXAMPLE 1. How many joules are required to melt 255g of ice at 0ºC? 2. pick out important information how much stuff m255g of water Ice H 2 O so heat of fusion is TABLE B q = mH f 1. asking me to find out HOW MANY J q 334 J/g

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3. plug in q = mH f q = (255g) x 344 J g q = 85170 J

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HEAT OF VAPORIZATION Boiling means phase change: liquid gas The temperature remains constant during the boiling process. The amount of heat needed to convert a unit mass of a substance from its liquid phase to its vapor phase at constant temperature is called its heat of vaporization (H v ) The equation used is q = mH v.

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EXAMPLE 2. How many joules of energy are required to vaporize 423g of water at 100ºC? 2. pick out important information how much stuff m 423g of water 100 o C this means Boiling so heat of vaporization TABLE B q = mH v 1. asking me to find out HOW MUCH J q 2260 J/g

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3. plug in q = mH v q = (423g) x 2260J g q = 955980 J

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INDEPENENT PRACTICE COMPLETE FOR HOMEWORK IF YOU ARE NOT DONE IN CLASS. ASSIGNMENT IS TO BE COMPLETED BY TOMORROW!!!

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