Energy Changes in Everyday Life

This final lesson brings together everything you have learned about energy changes and applies it to real-world contexts. Understanding how exothermic and endothermic reactions are used in everyday life is essential for the AQA GCSE Combined Science Trilogy (8464) specification.

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Exothermic Reactions in Everyday Life

Many everyday processes rely on exothermic reactions — reactions that release energy to the surroundings.

Respiration

Respiration is the exothermic reaction that occurs in every living cell to release energy for life processes:

$\text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2 \rightarrow 6\text{CO}_2 + 6\text{H}_2\text{O} \quad (\Delta H = -2803 \text{ kJ/mol})$C6​H12​O6​+6O2​→6CO2​+6H2​O(ΔH=−2803 kJ/mol)

This energy is used for:

• Muscle contraction (movement)
• Maintaining body temperature (37°C in humans)
• Active transport across cell membranes
• Building large molecules from smaller ones

Combustion

Burning fuels is an exothermic reaction used for:

Application	Fuel	Product
Heating homes	Natural gas (methane)	CO₂ + H₂O
Cooking	Gas, wood, charcoal	CO₂ + H₂O
Powering vehicles	Petrol, diesel	CO₂ + H₂O + other pollutants
Generating electricity	Coal, gas, oil	CO₂ + H₂O

Hand Warmers