Fossil Fuels, Biofuels and Energy Resources
What are fossil fuels?
fossil fuels are fuels formed from the buried remains of plants and animals that lived millions of years ago.
Name the three methods of heat transfer.
Conduction, convection and radiation.
What is the difference between kinetic energy and potential energy?
Kinetic energy is the energy an object has because of its motion. Potential energy is stored energy due to an object's position or condition.
Explain why different parts of the Earth receive different amounts of solar energy throughout the year.
Earth’s axis is tilted at approximately 23.5°. As Earth revolves around the Sun, the angle at which sunlight reaches different regions and the number of daylight hours change, causing seasonal variations in solar energy.
Explain how gravity keeps the Moon in orbit around the Earth instead of allowing it to move away into space.
Earth's gravitational force attracts the Moon towards it. This force, together with the Moon's forward motion, keeps it moving in orbit around Earth.
Give three examples of fossil fuels.
Coal, crude oil and natural gas.
What is convection, and how does it occur in water or air?
Convection is the transfer of heat through liquids or gases. Warm fluid rises while cooler fluid sinks, forming convection currents.
Explain how a basketball held above the ground gains gravitational potential energy.
The basketball gains gravitational potential energy when it is lifted above the ground because of its position in Earth's gravitational field.
The Earth's axis is tilted at approximately 23.5° from a vertical position. Explain how this tilt contributes to the formation of seasons.
The tilt causes each hemisphere to receive different amounts and intensities of sunlight at different times of the year. The hemisphere tilted towards the Sun experiences summer, while the hemisphere tilted away experiences winter.
The Moon rotates on its axis and revolves around the Earth. Explain why observers on Earth usually see the same side of the Moon.
The Moon takes approximately the same amount of time to rotate on its axis as it takes to revolve around Earth, about 27.3 days.
What are biofuels made from?
Biofuels are made from organic material, such as plants and animal waste.
Why is a thatched roof with a ceiling cooler in summer than a corrugated iron roof without a ceiling?
Thatched roofs are good insulators and reduce heat transfer. A ceiling provides an extra layer of insulation, helping keep the house cool.
What is the SI unit used to measure energy?
The joule (J).
Describe the difference between Earth's rotation and its revolution. Include the time taken to complete each movement and explain one effect of each.
Rotation is the spinning of Earth on its axis and takes approximately 24 hours, causing day and night. Revolution is Earth's movement around the Sun and takes approximately 365¼ days, forming one year.
Explain how the relative positions of the Sun, Earth and Moon determine whether spring tides or neap tides occur.
Spring tides occur when the Sun, Earth and Moon are aligned, causing a greater tidal range. Neap tides occur when the Sun and Moon are positioned at approximately right angles relative to Earth, resulting in a smaller tidal range.
State one difference between fossil fuels and biofuels.
Fossil fuels take millions of years to form and are non-renewable, while biofuels are produced from organic material that can be replenished.
Why is a heater placed near the floor of a room? Explain how convection currents form.
Warm air rises because it is less dense. Cooler air sinks towards the heater, warms up and rises. This circulation forms convection currents.
Identify one useful form of energy and two forms of wasted energy produced when an electric drill is operating.
Useful energy: Kinetic energy, which turns the drill bit.
Wasted energy: Sound energy and thermal (heat) energy.
Why is it incorrect to say that summer occurs because the Earth is closer to the Sun?
Seasons are mainly caused by Earth's axial tilt, not its distance from the Sun. The tilt affects the intensity of sunlight and the length of daylight in each hemisphere.
Analyse how the rise and fall of ocean tides influence the survival of organisms living in the intertidal zone.
High tides allow organisms to feed and move through the water while providing moisture. During low tides, organisms may be exposed to air, heat and predators. They must adapt by finding shelter, retaining moisture or attaching themselves firmly to rocks.
Give two disadvantages of using fossil fuels.
Burning fossil fuels releases greenhouse gases that contribute to climate change.
Fossil fuels are non-renewable and will eventually run out.
How does radiation transfer heat from the Sun to the Earth?
Heat travels through electromagnetic waves. Radiation does not require a medium and can travel through the vacuum of space.
Give two advantages and two disadvantages of using wind power in South Africa.
Advantages
Disadvantages
Wind is a renewable energy source.
Wind does not blow constantly, so electricity generation varies.
Wind power generates electricity without directly burning fossil fuels.
Wind turbines can be noisy and affect the landscape.
During the June solstice, the Northern Hemisphere experiences summer while the Southern Hemisphere experiences winter. Explain why these seasons occur simultaneously.
During the June solstice, the Northern Hemisphere is tilted towards the Sun and receives more direct sunlight and longer daylight hours. The Southern Hemisphere is tilted away from the Sun and receives less direct sunlight and shorter daylight hours, resulting in winter.
Explain how the gravitational forces of the Moon and the Sun influence the height of ocean tides on Earth.
The Moon’s gravitational force is the main cause of ocean tides, while the Sun’s gravity also affects them. When the Sun, Earth and Moon align, their gravitational effects combine to produce spring tides with a larger tidal range. When the Sun and Moon are at right angles relative to Earth, neap tides occur, producing a smaller tidal range.