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11 30 Unit 4 Lesson 8

Why does burning 1 mole of gasoline result in more energy than burning 1 mole of hydrogen?

Learning Objectives:

  • Analyze the similarities & differences between 1 mole and 1 gram of hydrogen & gasoline.
  • Describe two differences between hydrogen and octane combustion based on the chemical equations.
  • Compare and contrast 1 mole of salt to 1 mole of water.
  • Calculate the molar mass of a substance using the periodic table.
  • Explain why burning one gram of hydrogen result in more energy than burning one gram of octane (gasoline).
  • Explain why burning one mole of octane result in more energy than burning one mole of hydrogen.

Warm-up:

  • Attendance 
  • Open Student IMT Unit 4, make sure lesson 7 is complete. 
  • Write down the question for the day and complete the wonderings section for Lesson 8.  

IN-CLASS WORK:

  • Review Answers to Practice balancing equations sheet from last class.
  • Open L4.8 Student Activity Sheet and make a copy  
  • Review L4.8 and complete all parts of the IMT for lesson 8.

OUT-OF-CLASS WORK:

  • Open IMT for Unit 4 and make sure all sections for lesson 8 are complete. 
  • Make sure student sheet L4.8 is complete and complete the check for understanding on Schoology.

L4.8 Student Sheet

*Lesson 4.8: Why does burning 1 mole of gasoline result in more energy than burning 1 mole of hydrogen?

Practice Balancing these equations:

  • 2N2 + 5O2 → 2N2O5

  • 2H3PO4 + 3Mg(OH)2 → Mg3(PO4)2 + 6H2O

  • 2C6H6 + 15O2 → 12CO2 + 6H2O

  • Al(OH)3 + 3HBr → AlBr3 + 3H2O  

CONNECTING ENERGY to BALANCED EQUATIONS

Fuel Combustion Reaction Energy (kJ/g) Energy (kJ/mol) CO2/gal (lbs)
Gasoline 2C8H18 (l) + 25O2 (g) → 16CO2 (g) + 18H2O (g) 47 5430 20
Hydrogen 2H2 (g) + O2 (g) → 2H2O (g) 142 286 0

  1. Describe two similarities between hydrogen and octane combustion based on the balanced chemical equations.

  2. Describe two differences between hydrogen and octane combustion based on the chemical equations. 

  3. What do you notice about the reporting of the energy output units for the combustion of hydrogen and octane? 

INVESTIGATING THE DIFFERENCES BETWEEN MOLES AND GRAMS WITH SALT & WATER

  1. Observe the two samples of salt and glucose.  DO NOT OPEN THE CONTAINERS. Each contains one mole of salt and one mole of glucose. What are your initial observations about a mole of salt compared to a mole of glucose?

  2. Find the mass of each of these substances and record them below.  DO NOT OPEN THE CONTAINERS. Zero the balance using the empty container provided.

Mass of 1 mole of salt

57.50g

Mass of 1 mole of water

17.48

  1. What initial ideas do you have about the relationship between a gram and the mole after looking at these two substances?

Atomic mass of total elements in the compound will make the molar mass of the compound.

  1. Look at the table below of the molecular formulas, the ball and stick models, and the number of particles in a mole for sugar and salt. 

    1. What do you notice?

    WATER

    Formula: H2O 

    Ball and Stick Model:

    How many water molecules in a Mole: $$ 6.02 * 10^{23} $$

    SALT

    Formula: NaCl

    Ball and Stick Model:

    How many Salt Particles in a Mole: $$ 6.02 * 10^{23} $$

  2. Now consider our fuels. Look at the table below of the molecular formulas, the ball and stick models, and the number of particles in a mole for hydrogen gas and octane. 

    1. What do you notice?
    2. Draw Lewis structures of each of the molecules and insert them in the table below.

Hydrogen gas

Formula: H2 

Ball and stick model of H2

Draw Lewis structure of H2

How many Hydrogen molecules are in a Mole?: 6.02 x 1023

Octane liquid

Formula: C8H18

Ball and stick model of C8H18:

Draw a Lewis structure of C8H18:

How many Octane molecules are in one Mole?: 6.02 x 1023

  1. A mole is a way to group particles together.  A mole is a counting number. A mole is the same count of particles for every substance similar to a dozen.  We can have a dozen eggs, people, or pencils.  A dozen means that there are 12 in the sample.  Likewise, we can have a mole of atoms, electrons, sugar molecules, or elephants.  

  2. What is the numerical count in a mole? \(\(6.02 * 10^{23}\)\)

  3. Connecting moles and grams to the periodic table:

    1. Using the periodic table, support why the mass of one mole of hydrogen, H2 is about 2 grams. 
    2. Using the periodic table, support why the mass of one mole of oxygen, O2 is about 32 grams.
    3. Look at the element square for Hydrogen and Oxygen from the periodic table.
    4. What is the name of the number that you are using to determine the mass in one mole?  _____________________________
    5. Your turn - Calculate the mass of one mole of water, H2O.
    6. Describe in your own words how you obtained your answer for the mass of one mole of water.

  4. Definition of Molar Mass

    1. The molar mass is the mass of one mole of a substance.  The molar mass changes depending on the substance because the atomic structure (the number of protons, electrons, and neutrons) of each atom is different. 
    2. What are the units for molar mass? g/mol

  5. Write the molar mass of carbon (C) atoms using the correct units.

    12 g/mol

    1. Rewrite the molar mass of hydrogen gas, H2 using the correct units. 

    2 g/mol

    1. Determine the molar mass of oxygen gas, O2 using the correct units. 

    32 g/mol

    1. Determine the mass of one mole of octane, C8H18 using the correct units.

    114 g/mol

INVESTIGATING THE DIFFERENCES BETWEEN MOLES AND GRAMS WITH HYDROGEN AND OCTANE by MODELING A GRAM AND A MOLE OF FUEL

  1. Now that we have a definition of a mole and how it relates to mass, below is a model to show the difference between a gram of hydrogen gas and a gram of liquid octane. 

  2. What do you notice?

  3. Which has more particles, a gram of hydrogen gas or a gram of octane?

  4. Justify your choice

Hydrogen gas, H2

Octane liquid, C8H18

Model of one gram H2

Model of one gram C8H18


Mass: 1.0 g 

Mass: 1.0 g

  1. Below is a model to show the difference between a mole of hydrogen gas and a mole of octane liquid. 

  2. What do you notice?

  3. How many particles does each sample have?

  4. Which has more mass, a mole of hydrogen gas or a mole of octane?

  5. Justify your choice.

Hydrogen gas, H2

Octane liquid, C8H18

Model of one mole H2






Model of one mole C8H18








Number of Hydrogen Particles in a Mole:

6.02 x 1023

Number of Octane Particles in a Mole:

6.02 x 1023

Mass of 1 mole: 2.0 g/mole

Mass of 1 mole: 114.2 g/mole

ANSWERING THE LESSON’S QUESTION

Fuel

Combustion Reaction

Energy (kJ/g)

Energy (kJ/mol)

Gasoline

2C8H18 (l)    +   25O2 (g)     →16CO2 (g)  +   18H2O (g) 

47

5430

Hydrogen

2H2 (g)   +    O2 (g)      →          2H2O (g)

142

286

  1. Why does burning one gram of hydrogen result in more energy than burning one gram of octane? 

  2. Why does burning one mole of octane result in more energy than burning one mole of hydrogen? 

  3. Complete a combined IMT for L4.8.   

NEXT STEPS:

  1. Reflect on today’s question: What are the similarities and differences between one mole and one gram of hydrogen and gasoline? Why does burning one mole of gasoline result in more energy than burning one mole of hydrogen?

  2. Open up the IMT for this unit, complete all boxes for lesson 8

  3. Make sure all parts of the L4.8 student sheet are complete & complete the check for understanding on Schoology.

REVIEW & REINFORCE:

Use the following sections of the textbook to help you review materials that were covered in this lesson:

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Last update: June 5, 2023
Created: June 5, 2023