Energy Chap. 16

I.Definitions

A. Energy Energy is the ability to do work or produce heat I.Definitions

A. Energy B. Heat Heat is energy moving from one place to another I.Definitions

Heat = Energy For us, these terms will be used synonymously

A. Energy B. Heat C. Temperature A measure of the kinetic energy of the particles in a substance I.Definitions

A. Energy B. Heat C. Temperature D. Endothermic A description of a process that absorbs heat I.Definitions

A. Energy B. Heat C. Temperature D. Endothermic E. Exothermic A description of a process that gives off heat I.Definitions

Energy of motion II. Types of Energy A. Kinetic

Moving objects II. Types of Energy A. Kinetic 1.Mechanical

Heat energy (moving particles) II. Types of Energy A. Kinetic 1.Mechanical 2.Thermal

Stored energy II. Types of Energy A. Kinetic B. Potential

Energy that can be released as gravity acts II. Types of Energy A. Kinetic B. Potential 1.Gravitational

Energy stored in chemical bonds II. Types of Energy A. Kinetic B. Potential 1.Gravitational 2.Chemical

Energy in the form of light II. Types of Energy A. Kinetic B. Potential C. Radiant

III. Measuring Heat (q)

A. Units III. Measuring Heat (q)

SI unit of energy (work). Work done by applying one Newton force over one meter. A. Units 1.joule III. Measuring Heat (q)

Energy required to heat one gram of water by 1° C. A. Units 1.joule 2.calorie III. Measuring Heat (q)

A nutritional calorie. 1 Cal = 1000 cal A. Units 1.joule 2.calorie 3.Calorie III. Measuring Heat (q)

Equivalent to calories A. Units 1.joule 2.calorie 3.Calorie 4.kilocalorie III. Measuring Heat (q)

Equivalent to 1000 calories A. Units 1.joule 2.calorie 3.Calorie 4.kilocalorie III. Measuring Heat (q)

Energy required to heat 1 lb. water by 1º F. A. Units 1.joule 2.calorie 3.Calorie 4.kilocalorie 5.BTU III. Measuring Heat (q)

Heat Unit Conversions 1 cal = J 1000 cal = 1 Cal = 1 kcal

Self Check – Ex. 1 A reaction produces 3800 J of heat. How many calories is this?

Self Check – Ex. 2 A can of soda contains 150 Calories. How many joules of energy is this?

III. Measuring Heat (q) A. Units B. Heat is related to temperature

Which has more heat? III. Measuring Heat (q) A. Units B. Heat is related to temperature Temp. = 35º C Beaker #1Beaker #2 Temp. = 65º C

III. Measuring Heat (q) A. Units B. Heat is related to temperature C. Heat also depends on...

III. Measuring Heat (q) A. Units B. Heat is related to temperature C. Heat also depends on... 1.Mass of material

Which beaker could melt more ice (which has more heat)? Beaker #1 Beaker #2 T 1 = 85º C T 2 = 85º C

III. Measuring Heat (q) A. Units B. Heat is related to temperature C. Heat also depends on... 1.Mass of material 2.Type of material

III. Measuring Heat (q) A. Units B. Heat is related to temperature C. Heat also depends on... D. Specific Heat Amount of heat required to raise the temperature of 1 gram of substance by 1º C

III. Measuring Heat (q) A. Units B. Heat is related to temperature C. Heat also depends on... D. Specific Heat 1.Some material takes a lot of energy to raise its temperature

III. Measuring Heat (q) A. Units B. Heat is related to temperature C. Heat also depends on... D. Specific Heat 1.Some material takes a lot of energy to raise its temperature 2.Some material takes less

III. Measuring Heat (q) A. Units B. Heat is related to temperature C. Heat also depends on... D. Specific Heat 1.Some material takes a lot of energy to raise its temperature 2.Some material takes less 3.For water it’s 1 calorie/g ºC

Specific Heat Table SubstanceSpec. Heat (c) Water4.184 J/g ºC Aluminum0.89 J/g ºC Iron0.45 J/g ºC Copper0.387 J/g ºC Silver0.24 J/g ºC Gold0.129 J/g ºC Lead0.l28 J/g ºC

III. Measuring Heat (q) A. Units B. Heat is related to temperature C. Heat also depends on... D. Specific Heat E. Calculation q = m x c x ∆T

Self Check – Ex. 3 How much heat must be applied to a 25 g chunk of iron to raise its temperature by 100ºC? (c iron = 0.45 J/g ºC)

Self Check – Ex. 4 How much heat must be applied to a 25 g sample of water to raise its temperature by 100ºC? (c iron = 4.18 J/g ºC)

IV.Bond Energy

This is endothermic IV.Bond Energy A.When bonds are broken energy is.

This is endothermic IV.Bond Energy A.When bonds are broken energy is required. (positive)

IV.Bond Energy A.When bonds are broken energy is required. (positive) B. When bonds are formed energy is.

IV.Bond Energy A.When bonds are broken energy is required. (positive) B. When bonds are formed energy is released. (negative) This is exothermic

IV.Bond Energy A.When bonds are broken energy is required. (positive) B. When bonds are formed energy is released. (negative) C. The sum of the bond energies gives an estimate of the reaction energy

IV.Bond Energy A.When bonds are broken energy is required. (positive) B. When bonds are formed energy is released. (negative) C. The sum of the bond energies gives an estimate of the reaction energy 1.Positive values = endothermic

IV.Bond Energy A.When bonds are broken energy is required. (positive) B. When bonds are formed energy is released. (negative) C. The sum of the bond energies gives an estimate of the reaction energy 1.Positive values = endothermic 2.Negative values = exothermic

Self Check – Ex. 5 Draw Lewis structures for each substance and calculate the energy for the reaction below. 2CO + O 2 2CO 2

V. Enthalpy Stoichiometry

A. Enthalpy represented by H and enthalpy change by ∆H.

V. Enthalpy Stoichiometry A. Enthalpy represented by H and enthalpy change by ∆H. B. Enthalpy change for a reaction measured in kJ/mol.

V. Enthalpy Stoichiometry A. Enthalpy represented by H and enthalpy change by ∆H. B. Enthalpy change for a reaction measured in kJ/mol. C. Exothermic reactions have negative ∆H values. (+ ∆H C. Exothermic reactions have negative ∆H values. (+ ∆H for endothermic)

V. Enthalpy Stoichiometry A. Enthalpy represented by H and enthalpy change by ∆H. B. Enthalpy change for a reaction measured in kJ/mol. C. Exothermic reactions have negative ∆H values. (+ ∆H C. Exothermic reactions have negative ∆H values. (+ ∆H for endothermic) D. Solving problems

Enthalpy Stoichiometry

1.Write a balanced equation

Enthalpy Stoichiometry 1.Write a balanced equation 2.Identify the units of the unknown

Enthalpy Stoichiometry 1.Write a balanced equation 2.Identify the units of the unknown 3.Write the ‘given’

Enthalpy Stoichiometry 1.Write a balanced equation 2.Identify the units of the unknown 3.Write the ‘given’ 4.Fill in conversion factors

V. Enthalpy Stoichiometry A. Enthalpy represented by H and enthalpy change by ∆H. B. Enthalpy change for a reaction measured in kJ/mol. C. Exothermic reactions have negative ∆H values. (+ ∆H C. Exothermic reactions have negative ∆H values. (+ ∆H for endothermic) D. Solving problems 1.Finding heat

Self Check – Ex. 6 How much heat is produced when 75g of hydrogen is burned in oxygen? 2H 2 + O 2 2H 2 O ∆H = kJ

V. Enthalpy Stoichiometry A. Enthalpy represented by H and enthalpy change by ∆H. B. Enthalpy change for a reaction measured in kJ/mol. C. Exothermic reactions have negative ∆H values. (+ ∆H C. Exothermic reactions have negative ∆H values. (+ ∆H for endothermic) D. Solving problems 1.Finding heat 2.Finding mass

Self Check – Ex. 7 What mass of hydrogen is required to produce 8500 kJ of energy? 2H 2 + O 2 2H 2 O ∆H = kJ

VI. Enthalpy Calorimetry

A.Calorimetry is the science of heat measurement

VI. Enthalpy Calorimetry 1.Mass of water in calorimeter A.Calorimetry is the science of heat measurement B.ΔH can be determined experimentally if you measure:

VI. Enthalpy Calorimetry 1.Mass of water in calorimeter 2.Initial temperature A.Calorimetry is the science of heat measurement B.ΔH can be determined experimentally if you measure:

VI. Enthalpy Calorimetry 1.Mass of water in calorimeter 2.Initial temperature 3.Final temperature A.Calorimetry is the science of heat measurement B.ΔH can be determined experimentally if you measure:

VI. Enthalpy Calorimetry 1.Mass of water in calorimeter 2.Initial temperature 3.Final temperature 4.Mass of reactant used A.Calorimetry is the science of heat measurement B.ΔH can be determined experimentally if you measure:

Calculating ∆H for rxn 1.Determine the units for your answer.

Calculating ∆H for rxn 1.Determine the units for your answer. 2.Calculate the heat gained by the water. Q = mc∆T c water = 4.18 J/g ∙ ºC

Calculating ∆H for rxn 1.Determine the units for your answer. 2.Calculate the heat gained by the water. 3.Determine the heat lost by rxn. Q gained = - Q lost

Calculating ∆H for rxn 1.Determine the units for your answer. 2.Calculate the heat gained by the water. 3.Determine the heat lost by rxn. 4.Convert grams reactant into moles reactant.

Calculating ∆H for rxn 1.Determine the units for your answer. 2.Calculate the heat gained by the water. 3.Determine the heat lost by rxn. 4.Convert grams reactant into moles reactant. 5.Divide heat lost (#3) by the moles reactant (#4).

Self Check – Ex. 8 When a 10.0 g of NaOH is added to 200 g of water the temperature goes from 18.2ºC to 31.6ºC. What is ∆H for the reaction in kJ/mol?

VII. Hess’s Law

A.When a series of equations are added together, their enthalpy changes are also added 2NO (g) + O 2 (g) 2NO 2 (g) ΔH = -113 kJ Add these equations N 2 (g) + O 2 (g) 2NO (g) ΔH = +181 kJ

VII. Hess’s Law A.When a series of equations are added together, their enthalpy changes are also added B.Equations can be altered

VII. Hess’s Law 1.If an equation is reversed... A.When a series of equations are added together, their enthalpy changes are also added B.Equations can be altered CO 2 (g) CO (g) + ½ O 2 (g) ΔH = +283 kJ

VII. Hess’s Law 1.If an equation is reversed... 2.If the coefficients are multiplied by a factor... A.When a series of equations are added together, their enthalpy changes are also added B.Equations can be altered * Using fractions is perfectly acceptable 2C (g) + O 2 (g) CO (g) ΔH = -111 kJ X ½X ½X ½X ½

Self Check – Ex. 9 2H 2 (g) + O 2 (g) 2H 2 O (l) ΔH = -572 kJ H 2 (g) + O 2 (g) 2H 2 O 2 (l) ΔH = -188 kJ 2H 2 O 2 (l) 2 H 2 O (l) + O 2 (g) ΔH = ? kJ

Self Check – Ex. 10 2H 2 (g) + O 2 (g) 2H 2 O (g) ΔH = kJ 3O 2 (g) 2O 3 (g) ΔH = +284 kJ 3H 2 (g) + O 3 (g) 3H 2 O (g) ΔH = ? kJ

VII.Phase changes and heat

The End