Area of Study 1: What are the current and future options for supplying energy?

You will be able to:

• Compare fossil fuels and biofuels using energy content and environmental impact.

• Write balanced thermochemical equations for combustion.

• Calculate heat energy released using specific heat capacity.

• Use stoichiometry to quantify energy, mass and gas amounts.

• Apply the electrochemical series to design galvanic cells.

• Build and explain the operation of primary cells and fuel cells.

• Use Faraday’s Laws to calculate charge, current, mass and time.

• Evaluate sustainability of different energy sources.

1️⃣ Fuels and Energy Sources

A fuel is a substance that releases energy during a chemical reaction (usually combustion).

Fossil Fuels Characteristics:
✔ High energy output
✘ Non-renewable
✘ Produce greenhouse gases

Biofuels Characteristics:
✔ Renewable
✔ Lower net CO₂ emissions
✔ Produced from plants/microbes

2️⃣ Exothermic & Endothermic Reactions

Exothermic

• Release energy

• Combustion reactions

• ΔH is negative

Endothermic

• Absorb energy

• Breaking bonds

• ΔH is positive

Students write thermochemical equations with ΔH values.

3️⃣ Limiting Reagents

The reactant that is used up first determines how much product forms. Essential for:

• Stoichiometry

• Fuel efficiency calculations

• Gas yield questions

4️⃣ Combustion Reactions

Complete combustion

Produces CO₂ + H₂O
Releases maximum energy

Incomplete combustion

Produces CO + C (soot)
Occurs when oxygen is limited
Less efficient & more harmful

5️⃣ Measuring Energy: Calorimetry

Students use calorimetry to measure energy released from:

• Fuels

• Foods

Key equation:

q=mcΔTq = mc\Delta Tq=mcΔT

6️⃣ Stoichiometry & Gas Calcu

Used to calculate:

• Heat released

• CO₂ emissions

• Fuel efficiency

7️⃣ Redox Reactions & Electrochemical Cells

Key ideas:

• Oxidation = loss of electrons

• Reduction = gain of electrons

• Electrons flow from anode → cathode

Using the electrochemical series

8️⃣ Primary Cells, Fuel Cells & Rechargeable Cells

Primary (non-rechargeable) cells

• Convert chemical → electrical energy

• Stop working when reactants are used up

Fuel cells

• Continuous fuel supply (e.g., H₂ + O₂)

• High efficiency

• Low emissions

• Used in space & hydrogen cars

Rechargeable cells (secondary)

• Operate as galvanic when discharging

• Operate as electrolytic when charging

9️⃣ Faraday’s Laws

Used to calculate:

• Charge (Q = It)

• Mass of substance deposited

• Electrons transferred

Conceptual Questions

1. Why are biofuels considered more sustainable than fossil fuels?

2. Explain why incomplete combustion is less efficient.

3. Describe how a fuel cell differs from a primary cell.

4. Why does hydrogen bonding affect the energy value of alcohols?

5. Define limiting reagent and give an example.

Calculation Questions

6. Calculate the energy absorbed by 200 g of water heated by 9.5°C.

7. Write a balanced thermochemical equation for ethanol combustion.

8. Calculate the CO₂ produced from burning 1.00 mol of propane.

• Confusing anode/cathode (remember: galvanic = AN OX, RED CAT)

• Forgetting ΔH sign convention

• Incorrect unit conversions (J ↔ kJ, L ↔ m³)

• Misreading electrochemical series order

• Assuming higher voltage always = more sustainable

• Always label diagrams of galvanic cells

• Use units consistently in calorimetry & stoichiometry

• Redox: practise half-equations daily

• Memorise typical fuel equations (ethanol, methane, butane)

• Use the electrochemical series every time—you must know how to apply it