Energy from Fuels

To know how energy from fuels can be

measured.(Grade C)

To calculate the energy content of a fuel.

(Grade B)

To explain how to measure energy changes

in solution. (Grade A)

Keywords: Fuel, Combustion, Exothermic, Endothermic, Joule, Kilojoule,

To know how energy from fuels can be measured.

(Grade C)

To calculate the energy content of a fuel.

(Grade B)

To explain how to measure energy changes in solution.

(Grade A)

Keywords: Fuel, Combustion, Exothermic, Endothermic, Joule, Kilojoule,

Term Definition

Exothermic

Endothermic

Combustion

Joule

Kilojoule

Calorie

Mole

Relative molecular mass

To know how energy from fuels can be measured.

(Grade C)

To calculate the energy content of a fuel.

(Grade B)

To explain how to measure energy changes in solution.

(Grade A)

Term Definition

Exothermic A reaction that GIVES OUT energy to the surroundings

Endothermic A reaction that TAKES IN energy from the surroundings.

Combustion Where a substance burns in oxygen.

Joule The unit of energy

Kilojoule 1000J

Calorie The amount of energy needed to raise 1kg by 1C

Mole The amount of substance in the relative atomic/formula mass of a substance in grams

Relative molecular mass

The total of the relative atomic masses, added up in the ration shown in the chemical formula, for a substance.

Keywords: Fuel, Combustion, Exothermic, Endothermic, Joule, Kilojoule,

To know how energy from fuels can be measured.

(Grade C)

To calculate the energy content of a fuel.

(Grade B)

To explain how to measure energy changes in solution.

(Grade A)

Term Definition

Exothermic A reaction that GIVES OUT energy to the surroundings

Endothermic A reaction that TAKES IN energy from the surroundings.

Combustion Where a substance burns in oxygen.

Joule The unit of energy

Kilojoule 1000J

Calorie The amount of energy needed to raise 1kg by 1C

Mole The amount of substance in the relative atomic/formula mass of a substance in grams

Relative molecular mass

The total of the relative atomic masses, added up in the ration shown in the chemical formula, for a substance.

Keywords: Fuel, Combustion, Exothermic, Endothermic, Joule, Kilojoule,

To know how energy from fuels can be measured.

(Grade C)

To calculate the energy content of a fuel.

(Grade B)

To explain how to measure energy changes in solution.

(Grade A)

Keywords: Fuel, Combustion, Exothermic, Endothermic, Joule, Kilojoule,

Calorimeter allows you to compare energy (metal can with water in it).

Equation:

Q = mc∆TQ = Energy releasedm = Mass of water heated (1cm3 = 1g)c = Specific heat capacity (Energy needed to raise 1g by 1C)∆T = Change in temperature

For water its specific heat capacity (c) is 4.2J/gC

Per Mole:

Q x Molecular Mass Mass of fuel burnt

To know how energy from fuels can be measured.

(Grade C)

To calculate the energy content of a fuel.

(Grade B)

To explain how to measure energy changes in solution.

(Grade A)

Keywords: Fuel, Combustion, Exothermic, Endothermic, Joule, Kilojoule,

Example:

A + B C

60cm3 of A contains 0.1 moles. 40cm3 of B contains 0.1 moles. Temperature at start: 20.0CTemperature at end: 26.5C

Q = mc∆T

Q = mc∆T

m = 60g + 40g = 100gc = 4.2 J/gC∆T = 6.5C

Q = 273000 or 2.73kJ

This is for 0.1 moles.

So for 1 Mole = 10 x 2.73= 27.3J

This is exothermic

To know how energy from fuels can be measured.

(Grade C)

To calculate the energy content of a fuel.

(Grade B)

To explain how to measure energy changes in solution.

(Grade A)

Keywords: Fuel, Combustion, Exothermic, Endothermic, Joule, Kilojoule,

Question on p219 – Summary Q2.

Question on p221 – Summary Q2.

To know how energy from fuels can be measured.

(Grade C)

To calculate the energy content of a fuel.

(Grade B)

To explain how to measure energy changes in solution.

(Grade A)

Keywords: Fuel, Combustion, Exothermic, Endothermic, Joule, Kilojoule,

Exothermic or Endothermic?

Exothermic: Energy released to environment.

Endothermic: Energy supplied by the environment.

A + B

A + B

C

C

A + B C

A + B – These are the REACTANTSC – This is the product

Energy released and surrounding increase in temperature.

Energy gained and surrounding decrease in temperature.

To know how energy from fuels can be measured.

(Grade C)

To calculate the energy content of a fuel.

(Grade B)

To explain how to measure energy changes in solution.

(Grade A)

Keywords: Fuel, Combustion, Exothermic, Endothermic, Joule, Kilojoule,

Questions on p223 – Summary Q2 and Q3.

To know how energy from fuels can be measured.

(Grade C)

To calculate the energy content of a fuel.

(Grade B)

To explain how to measure energy changes in solution.

(Grade A)

Keywords: Fuel, Combustion, Exothermic, Endothermic, Joule, Kilojoule,

Activation Energy?

What is it?The minimum amount of energy needed for a collision between to chemicals to result in a reaction.

What do enzymes do?They provide an alternative route to make the products and REDUCE the activation energy needed.

A + B

C

Enzymes lower the activation energy.

To know how energy from fuels can be measured.

(Grade C)

To calculate the energy content of a fuel.

(Grade B)

To explain how to measure energy changes in solution.

(Grade A)

Keywords: Fuel, Combustion, Exothermic, Endothermic, Joule, Kilojoule,

Chemical Reactions:

For a chemical reaction to take place there needs to be BONDS BEING BROKEN and BONDS BEING FORMED.

To break a bond = ENERGY NEEDS TO BE SUPPLIED. To form a bond = ENERGY IS GIVEN OUT.

Example:

H2 + O2 H2O is this balanced?

2H2 + O2 2H2O

To know how energy from fuels can be measured.

(Grade C)

To calculate the energy content of a fuel.

(Grade B)

To explain how to measure energy changes in solution.

(Grade A)

Keywords: Fuel, Combustion, Exothermic, Endothermic, Joule, Kilojoule,

2H2 + O2 2H2O

Reactants

Products

Symbols 2H2 O2 2H2O

Bonds H-H 0=0 H-O, H-O

Number of Bonds

2 x H-H 1 x O=O 4 x H-O

To know how energy from fuels can be measured.

(Grade C)

To calculate the energy content of a fuel.

(Grade B)

To explain how to measure energy changes in solution.

(Grade A)

Keywords: Fuel, Combustion, Exothermic, Endothermic, Joule, Kilojoule,

2H2 + O2 2H2O

This reaction is exothermic and so releases energy.

This is a reaction (hydrogen being oxidised) that could be an alternative to petrol in cars.

Advantages Disadvantages

No pollutants Hydrogen is explosive and so difficult to store.

Not add to global warming Hydrogen is produced via electrolysis and so needed energy, released from fossil fuels.

Can be carried out by Fuel Cells in cars (Hydrogen is oxidised)

To know how energy from fuels can be measured.

(Grade C)

To calculate the energy content of a fuel.

(Grade B)

To explain how to measure energy changes in solution.

(Grade A)

Keywords: Fuel, Combustion, Exothermic, Endothermic, Joule, Kilojoule,

More on Bonds and Reactions

Bond Breaking Bond Forming Type of Reaction

Less energy needed More energy needed Exothermic

More energy needed Less energy needed Endothermic

To know how energy from fuels can be measured.

(Grade C)

To calculate the energy content of a fuel.

(Grade B)

To explain how to measure energy changes in solution.

(Grade A)

Keywords: Fuel, Combustion, Exothermic, Endothermic, Joule, Kilojoule,

More on Bonds and Reactions

Bond Bond Energy (kJ/mol)

Bond Bond Energy (kJ/mol)

C-C 347 H-Cl 432

C-O 358 H-O 464

C-H 413 H-N 391

C-N 286 H-H 436

C-Cl 346 O=O 498

Cl-Cl 243 N≡N 945

To know how energy from fuels can be measured.

(Grade C)

To calculate the energy content of a fuel.

(Grade B)

To explain how to measure energy changes in solution.

(Grade A)

Keywords: Fuel, Combustion, Exothermic, Endothermic, Joule, Kilojoule,

What happens in:

N2 + 3H2 2NH3

Reactants

ProductsSymbols

Bonds

Number of Bonds

Bond Energy

Total

To know how energy from fuels can be measured.

(Grade C)

To calculate the energy content of a fuel.

(Grade B)

To explain how to measure energy changes in solution.

(Grade A)

Keywords: Fuel, Combustion, Exothermic, Endothermic, Joule, Kilojoule,

What happens in:

N2 + 3H2 2NH3

Reactants

ProductsSymbols N2 3H2 2NH3

Bonds

Number of Bonds

Bond Energy

Total

To know how energy from fuels can be measured.

(Grade C)

To calculate the energy content of a fuel.

(Grade B)

To explain how to measure energy changes in solution.

(Grade A)

Keywords: Fuel, Combustion, Exothermic, Endothermic, Joule, Kilojoule,

What happens in:

N2 + 3H2 2NH3

Reactants

ProductsSymbols N2 3H2 2NH3

Bonds N-N H-H N-H, N-H, N-H

Number of Bonds

Bond Energy

Total

To know how energy from fuels can be measured.

(Grade C)

To calculate the energy content of a fuel.

(Grade B)

To explain how to measure energy changes in solution.

(Grade A)

Keywords: Fuel, Combustion, Exothermic, Endothermic, Joule, Kilojoule,

What happens in:

N2 + 3H2 2NH3

Reactants

ProductsSymbols N2 3H2 2NH3

Bonds N-N H-H N-H, N-H, N-H

Number of Bonds

1 x N≡N 3 x H-H 6 x N-H

Bond Energy

Total

To know how energy from fuels can be measured.

(Grade C)

To calculate the energy content of a fuel.

(Grade B)

To explain how to measure energy changes in solution.

(Grade A)

Keywords: Fuel, Combustion, Exothermic, Endothermic, Joule, Kilojoule,

What happens in:

N2 + 3H2 2NH3

Reactants ProductsSymbols N2 3H2 2NH3

Bonds N-N H-H N-H, N-H, N-H

Number of Bonds

1 x N≡N 3 x H-H 6 x N-H

Bond Energy 945 3 x 436 6 x 391

Total

To know how energy from fuels can be measured.

(Grade C)

To calculate the energy content of a fuel.

(Grade B)

To explain how to measure energy changes in solution.

(Grade A)

Keywords: Fuel, Combustion, Exothermic, Endothermic, Joule, Kilojoule,

What happens in:

N2 + 3H2 2NH3

Reactants

ProductsSymbols N2 3H2 2NH3

Bonds N-N H-H N-H, N-H, N-H

Number of Bonds

1 x N≡N 3 x H-H 6 x N-H

Bond Energy 945 3 x 436 6 x 391

Total = 2253 = 2346

To know how energy from fuels can be measured.

(Grade C)

To calculate the energy content of a fuel.

(Grade B)

To explain how to measure energy changes in solution.

(Grade A)

Keywords: Fuel, Combustion, Exothermic, Endothermic, Joule, Kilojoule,

What happens in:

N2 + 3H2 2NH3

Reactants

ProductsSymbols N2 3H2 2NH3

Bonds N-N H-H N-H, N-H, N-H

Number of Bonds

1 x N≡N 3 x H-H 6 x N-H

Bond Energy 945 3 x 436 6 x 391

Total = 2253 = 2346

This is an EXOTHERMIC reaction as more energy released on forming (+96 kJ/Mol) than needed to break the bonds.

To know how energy from fuels can be measured.

(Grade C)

To calculate the energy content of a fuel.

(Grade B)

To explain how to measure energy changes in solution.

(Grade A)

Keywords: Fuel, Combustion, Exothermic, Endothermic, Joule, Kilojoule,

Questions:

Write balanced symbol equations and calculate the energy changes for the following chemical reactions:

a. Hydrogen + chlorine hydrogen chlorideb. Hydrogen + oxygen water

To know how energy from fuels can be measured.

(Grade C)

To calculate the energy content of a fuel.

(Grade B)

To explain how to measure energy changes in solution.

(Grade A)

Keywords: Fuel, Combustion, Exothermic, Endothermic, Joule, Kilojoule,

More on Bonds and Reactions

Bond Bond Energy (kJ/mol)

Bond Bond Energy (kJ/mol)

C-C 347 H-Cl 432

C-O 358 H-O 464

C-H 413 H-N 391

C-N 286 H-H 436

C-Cl 346 O=O 498

Cl-Cl 243 N≡N 945

To know how energy from fuels can be measured.

(Grade C)

To calculate the energy content of a fuel.

(Grade B)

To explain how to measure energy changes in solution.

(Grade A)

Keywords: Fuel, Combustion, Exothermic, Endothermic, Joule, Kilojoule,

Questions:

Write balanced symbol equations and calculate the energy changes for the following chemical reactions:

a. Hydrogen + chlorine hydrogen chloride ----- H2 + Cl2 HCl (185kJ/mol released)b. Hydrogen + oxygen water ------ 2H2 + O2 2H2O (486kJ/mol released)