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## PowerPoint Slideshow about ' The Flow of Energy – Heat' - candace-myers

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### The Flow of Energy – Heat

Chapter 17.1

Introduction to Thermochemistry

- Thermochemistry (or Thermodynamics) is the study of heat, energy, and temperature changes that occur during chemical reactions (One of the main courses of study in Physical Chemistry)
- Law of Conservation of Energy (1st Law of Thermodynamics) – The law of conservation of energy states that energy may neither be created nor destroyed. Therefore the sum of all the energies in the system is a constant. (Whether a reaction flask or the universe

Temperature vs. Heat

- Temperature is the measure of the average kinetic energy of the particles in a substance
- Measure using a thermometer
- Rises when heat is added
- Falls when heat is removed
- Heat(q) is the energy that is transferred between two objects
- Cannot be measured directly
- Can only detect the changes caused by heat

HOT

COLD

Thermochemical Reactions

- System – reactants and products
- Surroundings – the reaction container

Measuring Heat

- The Joule (J) is the SI unit of heat and energy
- The calorie (cal) is also used to measure heat capacity and is defined by the amount of heat needed to raise the temperature of 1g of pure water by 1C
- 1 J = 0.2390 cal 1 cal = 4.184 J
- NOTE: The energy contained in food is measured in Calories (Cal) = 1000 calories = 1 kcal

Heat Capacity vs Specific Heat

- Heat capacity is the amount of heat needed to raise the temperature of a substance by 1C

J/C or J/K

- Specific heat capacity (C) is the amount of heat needed to raise the temperature of one gram of a substance by 1C

J/gC or J/gK

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