ThermodynamicsThermodynamics

New section in table of contentsNew section in table of contents

EnergyEnergy

Energy Defined: Matter is stuff (atoms), Energy is the stuff that makes matter do stuff.

What are some different types of energy you know of?

Energy Defined: Matter is stuff (atoms), Energy is the stuff that makes matter do stuff.

What are some different types of energy you know of?

First Law of ThermodynamicsFirst Law of Thermodynamics

KC 1: 1st Law of Thermodynamics - energy can be neither created nor destroyed (conservation of energy).

KC 1: 1st Law of Thermodynamics - energy can be neither created nor destroyed (conservation of energy).

Mechanical EnergyMechanical Energy

Energy due to a object’s motion (kinetic) or position (potential).

Energy due to a object’s motion (kinetic) or position (potential).

Thermal EnergyThermal Energy

Heat EnergyThe heat energy of an object determines

how active its atoms are.

A hot object is one whose atoms and molecules are excited and show rapid movement.

A cooler object's molecules and atoms will show less movement.

Heat EnergyThe heat energy of an object determines

how active its atoms are.

A hot object is one whose atoms and molecules are excited and show rapid movement.

A cooler object's molecules and atoms will show less movement.

Electromagnetic EnergyElectromagnetic Energy

Light energy Includes energy

from gamma rays, x-rays, ultraviolet rays, visible light, infrared rays, microwave and radio bands

Light energy Includes energy

from gamma rays, x-rays, ultraviolet rays, visible light, infrared rays, microwave and radio bands

Electrical EnergyElectrical Energy

Energy caused by the movement of electrons. Easily transported through power lines and

converted into other forms of energy.

Energy caused by the movement of electrons. Easily transported through power lines and

converted into other forms of energy.

Nuclear EnergyNuclear Energy

The energy released during nuclear fission or fusion.

Fusion: Stars Fission: Nuclear

Power Plants; Earth Core

The energy released during nuclear fission or fusion.

Fusion: Stars Fission: Nuclear

Power Plants; Earth Core

Chemical EnergyChemical Energy

Energy that is available for release from chemical reactions.

Energy that is available for release from chemical reactions.

EnergyEnergy

MatterMatter Anything that has

mass and takes up space

Anything made of atoms or subatomic particles.

Anything that has mass and takes up space

Anything made of atoms or subatomic particles.

EnergyEnergy Energy is of central

importance in physics.

It is impossible to give a comprehensive definition of energy because of the many forms it may take.

KC 2: Energy is the ability to do work or produce heat.

Energy is of central importance in physics.

It is impossible to give a comprehensive definition of energy because of the many forms it may take.

KC 2: Energy is the ability to do work or produce heat.

EnergyEnergy

KC 3: Chemical potential energy is energy stored in a substance because of its composition

Chemical potential energy is important in chemical reactions

KC 3: Chemical potential energy is energy stored in a substance because of its composition

Chemical potential energy is important in chemical reactions

Chemical EnergyChemical Energy

TemperatureTemperature

KC 4: Temperature is a quantity proportional to molecular kinetic energy.

Temperature is the measure of the movement of atoms.

Average kinetic energy of molecules is measured in terms of temperature.

KC 4: Temperature is a quantity proportional to molecular kinetic energy.

Temperature is the measure of the movement of atoms.

Average kinetic energy of molecules is measured in terms of temperature.

A B C

Rank the following pictures according to their average kinetic energy (low to high)

Rank the following pictures according to their average kinetic energy (low to high)

HeatHeat

KC 5: Heat is a form of energy; that is in the process of flowing from a warmer object to a cooler object.

KC 5: Heat is a form of energy; that is in the process of flowing from a warmer object to a cooler object.

Chemical Energy Demos

2 more things to do2 more things to do

Ticket out the door- Post-it Note with name Write one complete sentence that shows how

energy, temperature, and heat are related.

Closure- Exit Pass- The system with the most heat will burn you the worst (200mL boiling water). Write the question below and think!

Why can dry ice, solid CO2 burn you, but CO2 in the gas phase cannot? Gases have more kinetic energy then liquids or solids.

Ticket out the door- Post-it Note with name Write one complete sentence that shows how

energy, temperature, and heat are related.

Closure- Exit Pass- The system with the most heat will burn you the worst (200mL boiling water). Write the question below and think!

Why can dry ice, solid CO2 burn you, but CO2 in the gas phase cannot? Gases have more kinetic energy then liquids or solids.

Cold and Hot Packs Cold and Hot Packs

How do you think instant hot and cold packs work? Keep in mind chemical reactions and energy.

How do you think instant hot and cold packs work? Keep in mind chemical reactions and energy.

Cold or Hot Pack?Cold or Hot Pack?

Experiment A:

A spoon full of sodium bicarbonate (NaHCO3) with 2 squirts of water in a sandwich bag.

Experiment B: A spoon full of calcium chloride (CaCl2) with 2

squirts of water in a sandwich bag.

Experiment A:

A spoon full of sodium bicarbonate (NaHCO3) with 2 squirts of water in a sandwich bag.

Experiment B: A spoon full of calcium chloride (CaCl2) with 2

squirts of water in a sandwich bag.

KC 6: Exothermic Reaction- is a chemical reaction that releases energy in the form of light or heat.

KC 6: Exothermic Reaction- is a chemical reaction that releases energy in the form of light or heat.

Reactants

Products

-H• En

erg

y

Energy of reactants

Energy of products

•Reaction Progress

Activation

Energy

KC 7: Endothermic Reaction-chemical reaction accompanied by the absorption of heat.

KC 7: Endothermic Reaction-chemical reaction accompanied by the absorption of heat.

+H

Reaction progress

En

erg

y

Reactants

ProductsActivation

Energy

Energy of reactants

Energy of products

Complete the sentences below for both experiment using the correct word.

Complete the sentences below for both experiment using the correct word.

1. Experiment ____ is similar to ____(hot /cold pack)

2. The salt which dissolves in water is_____.

3. The heat energy is _____(given off/ taken in).

4. The temperature _____ (falls/rises).

5. The reactions is _____ (endothermic/exothermic).

1. Experiment ____ is similar to ____(hot /cold pack)

2. The salt which dissolves in water is_____.

3. The heat energy is _____(given off/ taken in).

4. The temperature _____ (falls/rises).

5. The reactions is _____ (endothermic/exothermic).

Chemical Energy and the UniverseChemical Energy and the Universe

Chemists are interested in changes in energy during reactions.

Enthalpy is a measure of the total energy in a chemicals bonds.

KC 8: Enthalpy= heat of reaction= ΔH is the change in enthalpy during a reaction symbolized as ΔHrxn.

ΔHrxn = Hfinal – Hinitial

ΔHrxn = Hproducts – Hreactants

Chemists are interested in changes in energy during reactions.

Enthalpy is a measure of the total energy in a chemicals bonds.

KC 8: Enthalpy= heat of reaction= ΔH is the change in enthalpy during a reaction symbolized as ΔHrxn.

ΔHrxn = Hfinal – Hinitial

ΔHrxn = Hproducts – Hreactants

KC 9: Endothermic Reaction = positive ∆H

KC 10: Exothermic Reaction = negative ∆H

Enthalpy of a ReactionEnthalpy of a Reaction

KC 11: ΔHrxn = ∑n∆Hproducts – ∑n∆Hreactants

KC 11: ΔHrxn = ∑n∆Hproducts – ∑n∆Hreactants

ExampleExample

KC 12: Use the table to find the ∆Hrxn for the following reaction:

SO2(g) + NO2(g) → SO3(g) + NO(g)

KC 12: Use the table to find the ∆Hrxn for the following reaction:

SO2(g) + NO2(g) → SO3(g) + NO(g)

Substance ∆Hf (kJ/mol)

SO2(g) -296.8

NO2(g) 33.1

SO3(g) -395.8

NO(g) 90.3

Enthalpy of ReactionEnthalpy of Reaction

There will NOT be values given for substances that are in their “natural” state

Example – oxygen: It does not take energy to make O2(g)

carbon: It does not take energy to make C(s)

These heats of formation (∆Hf) will be zero

You MUST know this!!

There will NOT be values given for substances that are in their “natural” state

Example – oxygen: It does not take energy to make O2(g)

carbon: It does not take energy to make C(s)

These heats of formation (∆Hf) will be zero

You MUST know this!!

Specific HeatSpecific Heat

KC 13: The specific heat of any substance is the amount of heat required to raise one gram of that substance one degree Celsius.

Some objects require more heat than others to raise their temperature.

KC 13: The specific heat of any substance is the amount of heat required to raise one gram of that substance one degree Celsius.

Some objects require more heat than others to raise their temperature.

Specific HeatSpecific Heat

Intrinsic Property It is independent of how much of the material is

present.

Intrinsic Property It is independent of how much of the material is

present.

Measuring HeatMeasuring Heat

Measuring HeatMeasuring Heat

KC 14: A calorie is defined as the amount of energy required to raise the temperature of one gram of water one degree Celsius.

Food is measured in Calories, or 1000 calories (kilocalorie).

KC 15: A joule is the SI unit of heat and energy, equivalent to 0.2390 calories.

KC 14: A calorie is defined as the amount of energy required to raise the temperature of one gram of water one degree Celsius.

Food is measured in Calories, or 1000 calories (kilocalorie).

KC 15: A joule is the SI unit of heat and energy, equivalent to 0.2390 calories.

Specific Heat of WaterSpecific Heat of Water

Life on earth evolved in water, and all life still depends on water.

KC 16: Water has a specific heat capacity of 4.2 J/ goC, which means that it takes 4.2 joules of energy to heat 1g of water by 1oC.

KC 17: This is unusually high and it means that water does not change temperature easily.

Life on earth evolved in water, and all life still depends on water.

KC 16: Water has a specific heat capacity of 4.2 J/ goC, which means that it takes 4.2 joules of energy to heat 1g of water by 1oC.

KC 17: This is unusually high and it means that water does not change temperature easily.

KC 18: Calculating HeatKC 18: Calculating Heat

q = c × m × ΔT

q = heat absorbed or released

c = specific heat of substance

m = mass of substance in grams

ΔT = change in temperature in Celsius (Final – Initial)

q = c × m × ΔT

q = heat absorbed or released

c = specific heat of substance

m = mass of substance in grams

ΔT = change in temperature in Celsius (Final – Initial)

Calculating HeatCalculating Heat

KC 19: A 12.5g sample of aluminum was originally at 20°C. It was heated to a temperature of 34.3°C. How much heat was absorbed by the sample? (specific heat of aluminum = 0.9J/g°C)

KC 19: A 12.5g sample of aluminum was originally at 20°C. It was heated to a temperature of 34.3°C. How much heat was absorbed by the sample? (specific heat of aluminum = 0.9J/g°C)

Calculating HeatCalculating Heat

KC 20: A sample of zinc was heated from an initial temperature of 234°C to 439°C. There was 198.5J of heat absorbed and the specific heat of zinc is 0.388J/g°C. What was the mass of the sample?

KC 20: A sample of zinc was heated from an initial temperature of 234°C to 439°C. There was 198.5J of heat absorbed and the specific heat of zinc is 0.388J/g°C. What was the mass of the sample?

Calculating HeatCalculating Heat

KC 21: Calculate the amount of heat needed in calories to raise 23g of water from 49°C to 236°C.

KC 21: Calculate the amount of heat needed in calories to raise 23g of water from 49°C to 236°C.

Closure – Exit PassClosure – Exit Pass

Why did one ice cube melt faster than the other?

You must use the correct vocabulary in your response.

Why did one ice cube melt faster than the other?

You must use the correct vocabulary in your response.

CalorimetryCalorimetry

How do scientists measure the heat of reactions?

Scientists use a calorimeter to measure the temperature change of a given reaction

They can then use q=mc∆T to calculate the heat of that reaction

How do scientists measure the heat of reactions?

Scientists use a calorimeter to measure the temperature change of a given reaction

They can then use q=mc∆T to calculate the heat of that reaction

CalorimetryCalorimetry

KC 22: Calorimetry – using temperature change to calculate the heat of a reaction as it moves from reactants to products

KC 22: Calorimetry – using temperature change to calculate the heat of a reaction as it moves from reactants to products

CalorimetryCalorimetry

This process of calorimetry is how scientists measure the amount of calories in food

You will be doing a similar process to rank different snack foods from smallest kcal/g to largest amount of kcal/g

Video

This process of calorimetry is how scientists measure the amount of calories in food

You will be doing a similar process to rank different snack foods from smallest kcal/g to largest amount of kcal/g

Video

Calorimetry ExampleCalorimetry Example

Calculate the number of calories absorbed by the water, based on the information below.

Mass of empty beaker: 300g

Temperature of water before reaction: 27.0 ˚C

Mass of beaker with H2O: 465g

Temperature of water after reaction: 65.0 ˚C

Calculate the number of calories absorbed by the water, based on the information below.

Mass of empty beaker: 300g

Temperature of water before reaction: 27.0 ˚C

Mass of beaker with H2O: 465g

Temperature of water after reaction: 65.0 ˚C

Lab – Burning FoodLab – Burning Food

Measure approximately 15mL of water into the can. Record the mass of the water in data table (NOTE: 1mL of water = 1g)

Measure and record the initial temperature of the water in the can then remove the thermometer.

Place the food sample on the paper clip and record its mass in the data table.

Quickly ignite the food sample with a Bunsen burner and place the platform under the test tube. Place the thermometer in the can. Allow the food to burn completely.

Measure and record the highest temperature achieved by the water in the can during the burning of the food.

Record the mass of the food sample after burning and record in data table.

Measure approximately 15mL of water into the can. Record the mass of the water in data table (NOTE: 1mL of water = 1g)

Measure and record the initial temperature of the water in the can then remove the thermometer.

Place the food sample on the paper clip and record its mass in the data table.

Quickly ignite the food sample with a Bunsen burner and place the platform under the test tube. Place the thermometer in the can. Allow the food to burn completely.

Measure and record the highest temperature achieved by the water in the can during the burning of the food.

Record the mass of the food sample after burning and record in data table.

Data TableData TableFood Sample: Peanuts Doritos Cheetos Pretzels

Mass of water        

Initial temp of water        

Initial mass of food sample (this also includes the paper clip and

cork)       

Final temp of water        

Final mass of food sample (this also includes the paper clip and

cork)       

Change in temp of water        

Change in mass of food sample

       

q of water (from calculation)

       

Kcal/g of food sample (from calculation)

       

Hess’s LawHess’s Law

KC 23: Hess’s law – the amount of heat released or absorbed in a chemical reaction does not depend on the number of steps in the reaction

The ∆Hrxn can be determined from using other reactions

This is like systems of equations:

2x + 3y = 23

6y + x = -45

KC 23: Hess’s law – the amount of heat released or absorbed in a chemical reaction does not depend on the number of steps in the reaction

The ∆Hrxn can be determined from using other reactions

This is like systems of equations:

2x + 3y = 23

6y + x = -45

Hess’s LawHess’s Law

RULES:Flip an equation, change the sign on the

∆H

Multiply by a factor, multiply the ∆H by the same factor (can be a whole number or a fraction, ½, ¼ )

Add equations down to get the goal reaction, add ∆H’s down to get the ∆H for the goal reaction

RULES:Flip an equation, change the sign on the

∆H

Multiply by a factor, multiply the ∆H by the same factor (can be a whole number or a fraction, ½, ¼ )

Add equations down to get the goal reaction, add ∆H’s down to get the ∆H for the goal reaction

KC 24: Example Hess’s LawKC 24: Example Hess’s Law

Reaction ∆H Reaction ∆H

2 C(s) + O2(g) → 2 CO(g) -221kJ

C(s) + O2(g) → CO2(g) -393kJ

C(s) + CO2(g) → 2CO(g) ?

BRN – find ∆HBRN – find ∆H

C2H5OH(l) + 2 O2(g) --> 2 CO2(g) + 2 H2O(l)

-875. kJ

C (s) + O2 (g) --> CO2 (g)-

394.51 kJ

H2 (g) + ½ O2 (g) --> H2O (l) -285.8 kJ

2H2(g) + 2C(s) + O2(g) --> C2H5OH(l)

?

Lab RemindersLab Reminders

Keep the water boiling while you are doing the experiment

Be careful when placing the metal in the test tube (I’m going to give you 2 samples)

Leave test tube in boiling water for 5-10min

Use test tube holder to pour metal into calorimeter

Don’t forget to record initial temperature of water

Use about 15-20mL of water in the calorimeter

Record highest temperature of water reached for final temp

Assume initial temp of metal is 100°C

Keep the water boiling while you are doing the experiment

Be careful when placing the metal in the test tube (I’m going to give you 2 samples)

Leave test tube in boiling water for 5-10min

Use test tube holder to pour metal into calorimeter

Don’t forget to record initial temperature of water

Use about 15-20mL of water in the calorimeter

Record highest temperature of water reached for final temp

Assume initial temp of metal is 100°C

EnthalpyEnthalpy

KC 25: enthalpy is the measure of the energy that is released or absorbed by the substance when bonds are broken and formed during a reaction

When bonds are formed, energy is released

When bonds are broken, energy is absorbed

Exothermic reaction: -∆H

Endothermic reaction: +∆H

KC 25: enthalpy is the measure of the energy that is released or absorbed by the substance when bonds are broken and formed during a reaction

When bonds are formed, energy is released

When bonds are broken, energy is absorbed

Exothermic reaction: -∆H

Endothermic reaction: +∆H

EntropyEntropy

KC 26: entropy (∆S) is a measure of the randomness or disorder of the system; the greater the disorder of a system, the greater its entropy

As molecules or ions become more dispersed, their disorder increases and their entropy increases

KC 26: entropy (∆S) is a measure of the randomness or disorder of the system; the greater the disorder of a system, the greater its entropy

As molecules or ions become more dispersed, their disorder increases and their entropy increases

Reaction Entropy change ∆S

NaCl(s) → Na+(aq) + Cl-(aq) +43

2Na(s) + Cl2(g) → 2NaCl(s) -181

Gibbs Free EnergyGibbs Free Energy

KC 27: Gibbs free energy (∆G) is a measure of the spontaneity of the process

KC 28: A spontaneous reaction is one that does occur or is likely to occur without continuous outside assistance, such as input of energy

A reaction is spontaneous if the Gibbs energy change is negative

If a reaction has a ∆G greater than 0, the reaction is nonspontaneous

KC 27: Gibbs free energy (∆G) is a measure of the spontaneity of the process

KC 28: A spontaneous reaction is one that does occur or is likely to occur without continuous outside assistance, such as input of energy

A reaction is spontaneous if the Gibbs energy change is negative

If a reaction has a ∆G greater than 0, the reaction is nonspontaneous

Gibbs Free EnergyGibbs Free Energy

Reactions that have large negative ∆G values often release energy (-∆H) and increase disorder (+∆S)

∆G = ∆H - T∆S

Example:

2 K(s) + 2 H2O(l) → 2K+(aq) + 2 OH-(aq) + H2(g)

∆H = -392kJ, ∆S = 0.047kJ/K, T = 298K

Reactions that have large negative ∆G values often release energy (-∆H) and increase disorder (+∆S)

∆G = ∆H - T∆S

Example:

2 K(s) + 2 H2O(l) → 2K+(aq) + 2 OH-(aq) + H2(g)

∆H = -392kJ, ∆S = 0.047kJ/K, T = 298K

KC 29: Spontaneity (thermodynamically favored)

KC 29: Spontaneity (thermodynamically favored)

∆H ∆S T ∆G Spontaneous?

- +Low -

Yes High -

+ -Low +

No High +

_ +Low + No

High - Yes

+ -Low - Yes

High + No

Gibbs Free EnergyGibbs Free Energy

KC 30: Given that the changes in enthalpy and entropy are -139kJ and 277J/K respectively for the reaction given below, calculate the change in Gibbs energy. Then, state whether the reaction is spontaneous at 25°C.

C6H12O6(aq) → 2 C2H5OH(aq) + 2 CO2(g)

KC 30: Given that the changes in enthalpy and entropy are -139kJ and 277J/K respectively for the reaction given below, calculate the change in Gibbs energy. Then, state whether the reaction is spontaneous at 25°C.

C6H12O6(aq) → 2 C2H5OH(aq) + 2 CO2(g)

PracticePractice

Which of the following will be true when a pure substance in liquid phase freezes spontaneously?

A.∆G, ∆H, and ∆S are all positive

B.∆G, ∆H, and ∆S are all negative

C.∆G and ∆H are negative, but ∆S is positive

D.∆G and ∆S are negative, but, ∆H is positive

Which of the following will be true when a pure substance in liquid phase freezes spontaneously?

A.∆G, ∆H, and ∆S are all positive

B.∆G, ∆H, and ∆S are all negative

C.∆G and ∆H are negative, but ∆S is positive

D.∆G and ∆S are negative, but, ∆H is positive

PracticePractice

Which of the following pairs of conditions will favor a spontaneous reaction?

A. A decrease in entropy and a decrease in enthalpy

B. A decrease in entropy and an increase in enthalpy

C. An increase in entropy and a decrease in enthalpy

D. An increase in entropy and an increase in enthalpy

Which of the following pairs of conditions will favor a spontaneous reaction?

A. A decrease in entropy and a decrease in enthalpy

B. A decrease in entropy and an increase in enthalpy

C. An increase in entropy and a decrease in enthalpy

D. An increase in entropy and an increase in enthalpy

Review Video - closureReview Video - closure

Entropy

3, 2, 1 3 things you learned

2 things you found interesting

1 question you have

Entropy

3, 2, 1 3 things you learned

2 things you found interesting

1 question you have

Bellringer Bellringer

What three phases can H2O exist?

Can liquid water that is boiling ever get hotter than 100 C?

What are the bubbles made of when water boils?

What three phases can H2O exist?

Can liquid water that is boiling ever get hotter than 100 C?

What are the bubbles made of when water boils?

Heating Curve

Heating Curves

• tem

per

atu

re

•added energy

•solid

•liquid

•gas

Heating Curves

• tem

per

atu

re

•added energy

melting/freezing pt

boiling/

cond. pt

•solid

•liquid

•gas

Heating Curves

• tem

per

atu

re

•added energy

•solid

•liquid

•gas

•melting/freezing

•occurring here

•boiling/condensing

•occurring here

boiling/

cond. pt

melting/freezing pt

Cice = 2.09J/g°C ∆Hfus = 334J/g

Cwater = 4.184J/g°C ∆Hvap = 2260J/g

Csteam = 2.01J/g°C

q=mc∆Tq = m∆H

A 12g sample of ice initially at -5°C is heated to a temperature of 95°C. Calculate the amount of heat that is absorbed during this process.

A 12g sample of ice initially at -5°C is heated to a temperature of 95°C. Calculate the amount of heat that is absorbed during this process.

Cice = 2.09J/g°C

∆Hfus = 334J/g

Cwater = 4.184J/g°C

∆Hvap = 2260J/g

Csteam = 2.01J/g°C

A 3.5g sample of water at 13.6°C is heated to a temperature of 112°C. Calculate the amount of heat absorbed during this process.

A 3.5g sample of water at 13.6°C is heated to a temperature of 112°C. Calculate the amount of heat absorbed during this process.

Cice = 2.09J/g°C

∆Hfus = 334J/g

Cwater = 4.184J/g°C

∆Hvap = 2260J/g

Csteam = 2.01J/g°C

Cooling Curves

• tem

per

atu

re

Removal of energy

Heating and Cooling Curve AssignmentHeating and Cooling Curve Assignment

You will be given 2 element cards to create a heating and cooling curve. The melting points and boiling points are on the card for each element.

You will need to draw a heating curve for one and a cooling curve for the other.

You will be given 2 element cards to create a heating and cooling curve. The melting points and boiling points are on the card for each element.

You will need to draw a heating curve for one and a cooling curve for the other.

Closure: JeopardyClosure: Jeopardy

Answer- This letter Indicated when the matter is a solid.

Answer- 95°C

Answer- 70°C

Answer- This letter Indicated when the matter is a solid.

Answer- 95°C

Answer- 70°C

a

b c

d e

A

B C

D