Thermochemistry

Do Now – Check and edit prelabs Objective – Thermochemistry Exothermic, endothermic, calorie, joule, heat capacity, and specific heat Homework – Pg 510 # 9-11

Energy Transformations Energy is the capacity to do work or supply heat Energy has no mass or volume

Energy Transformations Energy is the capacity to do work or supply heat Energy has no mass or volume Thermochemistry = study of energy changes that occur during chemical reactions Heat (q) always flow from warmer to cooler

Exothermic and Endothermic Processes System and Surroundings Law of conservation of energy

Exothermic and Endothermic Processes System and Surroundings Law of conservation of energy

Exothermic and Endothermic Processes Endothermic Reactions – System absorbs energy from surroundings Exothermic Reactions- System gives off energy to the surroundings

Units of Measuring Heat Flow calorie = amount of heat it takes to raise the temp of 1 g of water 1 °C

Units of Measuring Heat Flow calorie = amount of heat it takes to raise the temp of 1 g of water 1 °C 1 Calorie = 1 Kilocalorie = 1000 calories

Units of Measuring Heat Flow calorie = amount of heat it takes to raise the temp of 1 g of water 1 °C 1 Calorie = 1 Kilocalorie = 1000 calories Joule (J) is the SI unit for measuring energy 1 J = cal J = 1 cal

Heat Capacity and Specific Heat (C) Heat Capacity = amount of heat needed to increase the temp of an object 1 °C

Heat Capacity and Specific Heat (C) Heat Capacity = amount of heat needed to increase the temp of an object 1 °C Specific Heat = amount of heat needed to increase the temp of 1 gram of a material 1 °C

Heat Capacity and Specific Heat (C) C = q = heat (Joules or calories)__ m x ∆T mass(g) x change in temp (°C )

Calculating the Specific Heat of a Metal C = q = heat (Joules or calories)__ m x ∆T mass(g) x change in temp (°C ) Sample Problem 17.1 pg 510 The temperature of a 95.4 gram piece of copper increases from 25.0 °C to 48.0 °C when the copper absorbs 849 J of heat. What is the specific heat of copper?

Calculating the Specific Heat of a Metal C = q = heat (Joules or calories)__ m x ∆T mass(g) x change in temp (°C ) Sample Problem 17.1 pg 510 The temperature of a 95.4 gram piece of copper increases from 25.0 °C to 48.0 °C when the copper absorbs 849 J of heat. What is the specific heat of copper?

Enthalpy

Heat content of a system at constant pressure

Enthalpy q sys = ∆H = -q surr = -m x C X ∆T

x 10 3 cal 1.76 kcal 7.36 x 10 3 J 7.36 kJ x J/(g*°C) x 10 2 kJ

Mg(s) + O 2 (g) → 2MgO(s) kJ or 2Mg(s) + O 2 (g) → 2MgO(s) ∆H= kJ x 10 2 kJ 20. Heat of combustion is the heat of reaction for the complete burning of one mole of a substance.