Energy makes things happen — it causes changes.
Forms of Energy and Change
For example, to change ice into water, you have to add energy in the form of heat. If the same amount of energy is removed, the water freezes again. These are known as physical changes.
To move a shopping trolley from a check-out to a car — a mechanical change — work must be done. The greater the force required and the further the distance, the more work is needed.
Work = Force × Distance
Energy cannot be destroyed, but it can be transformed from one form to another.
Energy in Nature
Green plants use light energy to drive chemical changes in carbon dioxide and nutrients, enabling growth. This process is known as photosynthesis.
Animals — including humans — consume plants and use this stored chemical energy to generate heat and perform work.
Fossil Fuels and Energy Production
Millions of years ago, plants and marine organisms absorbed energy from sunlight. Over time, their remains were buried and transformed into fossil fuels such as coal, oil, and natural gas.
By burning these fuels, we release stored chemical energy as heat. This heat is used to produce steam, which drives turbines connected to generators to produce electricity.
However, not all energy is converted efficiently. Some energy is lost as heat through exhaust gases, radiation, and friction. The proportion of usable energy produced is known as efficiency.
Environmental Impact
Fossil fuels are finite and take millions of years to form. Burning them releases carbon dioxide faster than natural systems can absorb it, contributing to global warming.
This has led to increasing interest in renewable energy sources.
Renewable Energy Sources
Moving materials possess kinetic energy. Flowing water has been used for centuries to power mills, and modern hydroelectric systems generate electricity.
Wave energy is still in early development, though some systems are already in use.
Wind energy has evolved from traditional windmills to modern turbines generating electricity across Ireland.
Tidal energy can also be harnessed using dams and turbines.
Solar energy can be used directly. Solar thermal systems heat water, while photovoltaic panels convert sunlight into electricity.
Biomass, such as wood and plant material, is a renewable energy source. When used sustainably, the carbon dioxide released during burning is offset by new plant growth.