Energy Resources and Conservation
Grade 8 · Science · Study Guide
Compare renewable and nonrenewable energy sources and explore strategies to reduce energy use and environmental impact.
Energy resources are materials or processes that provide usable energy for human activities. They are classified into two main categories: nonrenewable and renewable.
Nonrenewable energy sources — coal, oil, and natural gas (collectively called fossil fuels) — formed from the remains of ancient organisms over millions of years. Nuclear energy, which splits atoms to release energy, is also considered nonrenewable because it relies on finite uranium. Fossil fuels supply most of the world's energy today, but they release CO₂ and other pollutants when burned, contributing to climate change and air pollution.
Renewable energy sources are naturally replenished over short time periods. Solar energy uses photovoltaic cells or thermal collectors to harness sunlight. Wind energy uses turbines to convert wind into electricity. Hydroelectric power generates electricity from flowing or falling water. Geothermal energy uses heat from within Earth. Biomass energy comes from organic materials like wood and crops.
Energy conservation means using less energy through efficiency improvements and behavioral changes. Examples include using LED light bulbs, improving home insulation, driving fuel-efficient vehicles, and turning off unused appliances.
The law of conservation of energy states that energy cannot be created or destroyed — it can only change form. For example, chemical energy in gasoline converts to mechanical energy in a car engine, with some lost as heat.
Key terms
- Fossil fuels
- Nonrenewable energy sources (coal, oil, natural gas) formed from ancient organic matter over millions of years
- Renewable energy
- Energy from sources that are naturally replenished, such as solar, wind, hydroelectric, and geothermal
- Nonrenewable energy
- Energy from sources that cannot be replaced at the rate they are consumed, such as fossil fuels and nuclear energy
- Energy conservation
- The practice of reducing energy use through efficiency improvements and behavioral changes
- Solar energy
- Energy from the Sun, harnessed using photovoltaic cells or thermal collectors to produce electricity or heat
- Law of conservation of energy
- Energy cannot be created or destroyed; it can only be converted from one form to another
Flashcards
- Coal
- A solid fossil fuel formed from ancient plant matter; the most carbon-intensive fossil fuel when burned
- Wind turbine
- A device that converts kinetic energy from wind into electrical energy
- Hydroelectric power
- Electricity generated by the force of moving water turning turbines, typically at dams
- Photovoltaic cell
- A device that converts sunlight directly into electricity; used in solar panels
- Nuclear energy
- Energy released by splitting (fission) or fusing (fusion) atomic nuclei; uses uranium as fuel
- Energy efficiency
- The ratio of useful energy output to total energy input; higher efficiency means less energy wasted as heat
- Biomass energy
- Energy from organic materials like wood, crops, and waste; considered renewable because plants can be regrown
Questions
Which of the following is a renewable energy source?
- Coal
- Natural gas
- Wind
- Nuclear
Show answer
Answer: Wind
Wind is a renewable energy source because it is continuously replenished by natural atmospheric processes. Coal, natural gas, and nuclear fuels are nonrenewable.
Burning fossil fuels releases carbon dioxide, which contributes to climate change.
Show answer
Answer: True
Combustion of fossil fuels releases stored carbon as CO₂, a greenhouse gas that traps heat in the atmosphere and drives global warming.
Energy cannot be created or destroyed; it can only change form. This is the law of conservation of ______.
Show answer
Answer: energy
The law of conservation of energy is a fundamental principle of physics: energy changes form but the total amount in a closed system remains constant.
Which energy source uses the heat from inside Earth?
- Hydroelectric
- Geothermal
- Biomass
- Solar
Show answer
Answer: Geothermal
Geothermal energy taps into Earth's internal heat — from radioactive decay and residual heat from formation — to generate electricity or heat buildings.
Once a fossil fuel is consumed, it can be quickly replenished over a few years.
Show answer
Answer: False
Fossil fuels take millions of years to form under heat and pressure; they are considered nonrenewable because human consumption far outpaces their formation rate.
Get a personalized course on Energy Resources and Conservation built around your child.