Lecture_10_101711

# Lecture_10_101711 - Lecture 10 Calorimetry and Periodic...

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Lecture 10: Calorimetry and Periodic Trends • Goals: Be able to experimentally determine the temperature changes that occur when dissolving salts in water and determine the specific heat of a metal. Use the electron configurations to explain periodic trends. Outline (Timberlake Chapter 2.4, 3.8): - Energy and Nutrition (2.4) - Periodic Trends (3.8) Problems for Extra Practice: 2.23, 3.61, 3.63, 3.65, 3.67, 3.69, 3.71, 3.73, 3.75

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Heat vs. Temperature • Heat is defined as energy that flows from a warmer object to a cooler one – Heat is measured in joules or calories. • 4.184 joules (J) = 1 calorie (cal) (exact) • 1 kJ = 1000 J • 1 kilocalorie (kcal) = 1000 calories (cal) • Temperature is a measure of how hot or cold an object is compared to another object • Temperature indicates that heat flows from the object with a higher temperature to the object with a lower temperature
Specific Heat Specific heat • is the amount of heat that raises the temperature of 1 g of a substance by 1 °C

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Calculate Amount of Heat • Calculate the amount of heat given off or absorbed during dissolution ) I F ( M C Heat temp O H temp O H O H O H 2 2 2 2 - × × = water of capacity heat C O H 2 = used water of mass M O H 2 = water the of re temperatu final and initial e between th difference I F temp O H temp O H 2 2 = -
Chemical Energy • Exothermic reaction b gives off heat – Increase the temperature of the water • Observed temperature goes up – Sign of the energy is positive (+) • Endothermic reaction b absorbs heat – Decrease the temperature of the water • Observed temperature goes down – Sign of the energy is negative (-)

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Calorimetry • Calorimetry is the science of measuring the heat of chemical reactions or physical changes • A calorimeter • is used to measure heat transfer • contains a reaction chamber and thermometer in water • indicates the heat lost by a sample • indicates the heat gained by water
Heat Equation Q = m x S x Δ T Q = change in heat energy

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Lecture_10_101711 - Lecture 10 Calorimetry and Periodic...

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