Unit 6 ReviewUnit 6 ReviewKinetics and Thermochemistry

Wednesday 5/4Wednesday 5/4Have phase diagram hw out right Have phase diagram hw out right

away pleaseaway please

AFTER SCHOOL REVIEW WILL BE AWESOME! IT IS ALSO ON THE WEB FOR THOSE OF YOU WHO CAN’T MAKE IT. PLEASE COME! 2:20 – 3:15. 5 EXTRA CREDIT POINTS. AND EXTENSION ON LAST NIGHTS HW.

Unit 6 ReviewUnit 6 ReviewKinetics and ThermochemistryKinetics and Thermochemistry

Please take out paper to complete today’s review. Your notes may also be helpful.

Each part of today’s in class review is worth points. Please number each slide and complete each section.

You will have a limited amount of time for each section. Please keep up.

1 - Specific Heat1 - Specific HeatWhat mass of magnesium is present

if 250 J raises the temperature from 25 °C to 27 °C? Specific heat 1.02 J/gK

What is the heat capacity of an unknown metal if 65.5 grams absorbs 1550 J and undergoes a temperature change of 62.0 C°?

1 - Specific Heat Answers1 - Specific Heat AnswersWhat mass of magnesium is present if 250 J

raises the temperature from 25 °C to 27 °C? Specific heat 1.02 J/g °C ◦m= 250 J/(1.02 J/g °C x 2 °C) = 122.5 g = 120 g

What is the heat capacity of an unknown metal if 65.5 grams absorbs 1550 J and undergoes a temperature change of 62.0 C°?◦Cp = 1550J / (65.5 g x 62.0 °C) = 0.382 J/g °C

2 - Calculation of Energy2 - Calculation of EnergyHow many joules are required to

melt 650 grams of water?

How many joules are required to boil 650 grams of water?Substance Specific Heat (J/g◦C)

H2O (l) 4.184

H2O (steam) 2.02

Water

Heat of fusion = 334 J/g

Heat of vaporization = 2260 J/g

2 - Calculation 2 - Calculation of Energy of Energy AnswersAnswers

How many joules are required to melt 650 grams of water? ◦Hfusion = 334 J/g x 650 g = 217,100 J = 220,000 J

How many joules are required to boil 650 grams of water?◦H vap = 2260 J/g x 650 g = 1,469,000 J = 1,500,000J

Substance Specific Heat (J/g◦C)

H2O (l) 4.184

H2O (steam) 2.02

Water

Heat of fusion = 334 J/g

Heat of vaporization = 2260 J/g

3- Heat Curve…3- Heat Curve…1. Going from a solid to a gas is an

(exothermic, endothermic) process because energy is (absorbed, released).

2. During phase changes the temperature (increases, decreases, remains constant).

3. List the states of matter in order of increasing kinetic energy.

4. Why does sweating help cool you off?

3- Heat Curve Answers3- Heat Curve Answers1. Going from a solid to a gas is an

(exothermic, endothermic) process because energy is (absorbed, released).

2. During phase changes the temperature (increases, decreases, remains constant).

3. List the states of matter in order of increasing kinetic energy.

Solid to liquid to gas

4. Why does sweating help cool you off?Sweating happens when water

molecules evaporate (vaporize) from liquid droplets on your arm to gas. When these high energy molecules escape they lower the overall kinetic energy of the remaining molecules – lowering your body temperature as a result!

4- Phase Change 4- Phase Change DiagramsDiagrams

Which line represents the freezing point?

Which line represents the boiling point?

Describe what happens a the triple point?

Describe what happens at the critical point?

4 - Phase Change Diagrams 4 - Phase Change Diagrams AnswersAnswers

Which line represents the freezing point? (fusion line)

Which line represents the boiling point? (vaporization line)

Describe what happens a the triple point? (all 3 states exist simultaneously)

Describe what happens at the critical point? (the liquid state can no longer exist at these extremely high temps – no matter the pressure)

5 - Phase Change Diagram5 - Phase Change Diagram1. How could you

directly change “Q” to a solid?

2. Identify two ways you could change “Q” to a gas. Be specific.

3. Describe CLEARLY what is happening when A becomes A’.

4. Describe CLEARLY what is happening when B becomes B’.

Q

5 - Phase Change Diagram 5 - Phase Change Diagram AnswersAnswers

1. How could you directly change “Q” to a solid?

2. Decrease temp at same pressure.

3. Identify two ways you could change “Q” to a gas. Be specific.

4. Raise temp at same pressure. OR, lower pressure at same temp.

5. Describe CLEARLY what is happening when A becomes A’.

6. Pressure held constant. Solid A heated, solid A melts at MO, liquid A is heated, liquid A vaporizes at PO, gaseous A is heated to A’.

7. Describe CLEARLY what is happening when B becomes B’.

8. Pressure held constant. Solid B is heated, solid B sublimates at SO, gaseous B is heated to B’

Q

6 - Potential Energy 6 - Potential Energy DiagramsDiagrams

Draw an energy diagram: Heat of reactants: 4.5 KJHeat of products: 10.5 KJEnergy of activated complex: 15 KJHeat of reaction: _____ KJActivation Energy: ______ KJExothermic/Endothermic?How does a catalyst affect this graph?

6 - Potential Energy Diagrams 6 - Potential Energy Diagrams AnswersAnswersDraw an energy diagram:

Heat of reactants: 4.5 KJHeat of products: 10.5 KJEnergy of activated complex: 15 KJHeat of reaction: _____ KJ (10.5 – 4.5 = 6 KJ)Activation Energy: ______ KJ (15 – 4.5 = 10.5 KJ)Exothermic/Endothermic? ENDOTHERMIC (Products

higher than reactants)How does a catalyst affect this graph? (lowers the

activation energy so faster reaction)

7 - Potential Energy 7 - Potential Energy DiagramsDiagrams

Draw an energy diagram: Heat of reactants: 250 KJHeat of products: 25 KJEnergy of activated complex: 350 KJHeat of reaction: _____ KJActivation Energy: ______ KJExothermic/Endothermic? How does a catalyst affect this graph?

7 - Potential Energy 7 - Potential Energy Diagrams AnswersDiagrams Answers

Draw an energy diagram: Heat of reactants: 250 KJHeat of products: 25 KJEnergy of activated complex: 350 KJHeat of reaction: _____ KJ (25 – 250 = -225

KJ)Activation Energy: ______ KJ (350 – 250 = 100 KJ)Exothermic/Endothermic? EXOTHERMIC, energy of

products is LESS than reactants so excess energy given off!

How does a catalyst affect this graph? Again, catalyst lowers the activation energy

8 - Collision Theory8 - Collision TheoryIdentify 5 ways to increase the

rate of a reaction.

8 - Collision Theory Answers8 - Collision Theory AnswersIdentify 5 ways to increase the

rate of a reaction.Increase temp – more collisionsIncrease concentration of

reactants – more collisionsIncrease PressureDecrease volumeAdd a catalystAdd a more reactive substance

9- Reaction Rate9- Reaction RateCalculate the rate of the

reaction below.

Time (second)

9- Reaction Rate Answers9- Reaction Rate AnswersCalculate the rate of the

reaction below.

Rate = change in something/change in time

= (135 nm – 0 nm)/100 sec= 1.35 nm/sec

Time (second)