Year 8 Science: Energy and Continental Drift

Gravitational Potential Energy (GPE): This type of energy relates specifically to the pull of the Earth on an object.
Potential Energy (PE): This is defined as stored energy.
Elastic Potential Energy: Energy stored through the deformation of an object. * Stretching: Found in objects like rubber bands and bungee cords. * Compressing: Found in objects like rubber balls and trampolines.
Chemical Potential Energy: Energy stored in the bonds of chemical compounds. * Slow Release: Examples include food digestion, which keeps the body warm. * Rapid Release: Examples include the combustion of wood or petrol. * Electronic Release: Examples include batteries powering various devices and vehicles.

Electrical Fundamentals: * Voltage ( $V$ ): The electrical potential difference. * Current ( $I$ ): The flow of electricity. * Resistance ( $R$ ): The bottleneck or opposition to flow.
Nuclear Fission: The process involving a heavy, unstable atomic nucleus (such as Uranium). * Pathway A: Results in an explosive event. * Pathway B: Results in high-velocity kinetic particles and high-energy Gamma rays.

Definition: Energy can neither be created nor destroyed.
The Quantitative Principle: In any process, the amount of energy present at the beginning must exactly equal the amount of energy present at the end.
Mechanisms of Change: Instead of being created or destroyed, energy can only undergo transfer or transformation.
Energy Transfer: The movement of energy from one place to another. * Example: A golf club hitting a golf ball transfers kinetic energy from the club to the ball.
Energy Transformation: The conversion of one type of energy into another type of energy. * Example: Chemical potential energy in a source resulting in thermal energy and light energy. * Input vs. Output: Input energy leads to useful output energy and wasted output energy (by-products like thermal energy or sound).

Thermal Energy Transfer Methods: * Conduction: Heat moves through solids via physical touch. * Convection: Heat moves through liquids and gases. * Radiation: Heat travels as waves and requires no physical contact.
Energy Flow Diagrams: * Computer: Electrical energy $\rightarrow$ light + sound + heat. * Washing Machine: Electrical energy $\rightarrow$ movement + sound + heat. * Hair Dryer: Electrical energy $\rightarrow$ heat + movement (air) + sound. * Television: Electrical potential energy $\rightarrow$ light + sound + thermal (waste).
Adherence to Conservation: Energy is not "lost" in these systems; it is simply changed into different forms, often less useful ones like heat or sound.

Alfred Wegener (1912): Proposed that Earth's continents were once a single giant landmass called Pangea (or Pangaea).
Process: Over time, this landmass broke up and the continents drifted apart to form the modern globe.
The Evidence Board for Pangea: 1. Jigsaw Outlines: The coastlines of continents like South America and Africa appear to lock together. 2. Fossil Twins: Identical fossils of prehistoric animals found on continents now separated by wide oceans. 3. Rock Matching: Rocks of the same type and age exist on opposite sides of the Atlantic ocean. 4. Climate Anomalies/Inconsistencies: Finding coal in polar regions and evidence of glaciers in the tropics suggested continents shifted locations.
The Fatal Flaw: Wegener could not explain the mechanism of how the continents were actually moving, leading to the initial rejection of his theory.

Marie Tharp (The Cartographer's Breakthrough): Used raw sonar data to create the first detailed three-dimensional maps of the ocean floor. She discovered the Mid-Atlantic Ridge, a massive underwater mountain range.
Harry Hess: Proposed the theory of Seafloor Spreading. He used Pacific sonar profiles in conjunction with Tharp's Atlantic maps.
Seafloor Spreading Mechanism: Molten rock creates new seafloor at ridges, acting like a conveyor belt to move continents.
Magnetic Striping: Symmetrical magnetic "stripes" on the seafloor serve as the "smoking gun" evidence, proving that new crust is added equally to both sides of a ridge.
Sonar Technology: Sonar works by sending sound waves and waiting for them to bounce back; the time taken helps locate how far away an object or the floor is.

Unit Conversion Chart: * $1\,MJ = 1,000\,kJ$ * $1\,kJ = 1,000\,J$ * $1\,MJ = 1,000,000\,J$ * $1\,kcal = 4.184\,kJ$ * $1\,kJ = 0.239\,kcal$
Conversion Calculations: * $3.5\,MJ = 3,500\,kJ$ * $4,800\,J = 4.8\,kJ$ * $0.75\,MJ = 750,000\,J$ * $12,500\,J = 12.5\,kJ$ * $2.4\,MJ = 2,400,000\,J$ * $420\,kJ \text{ to kcal:} \frac{420,000\,J}{4,184} = 100.4\,kcal$ * $95\,kcal \text{ to kJ:} \frac{95 \times 4,184}{1,000} = 397.48\,kJ$ * $1,150\,kJ \text{ to kcal:} \frac{1,150,000\,J}{4,184} = 274.8\,kcal$ * $0.55\,MJ \text{ to kcal:} \frac{550,000\,J}{4,184} = 131.4\,kcal$

Definition: Energy efficiency refers to using less energy while still achieving the same results/performing the same task. It represents how much energy is transformed into a useful output.
Formula: $\text{Efficiency (\%)} = \frac{\text{useful output energy}}{\text{input energy}} \times 100$
Efficiency Calculations: * Computer: Consumes $375\,kWh$ , provides $346\,kWh$ useful energy. $\frac{346}{375} \times 100 = 92.26\%$ * Television: Consumes $6,000\,J$ , provides $4,600\,J$ useful energy. $\frac{4,600}{6,000} \times 100 = 76.6\% \approx 77\%$
Comparing Hair Dryer Models: * Model A: $\frac{450\,kWh}{520\,kWh} \times 100 = 87\%$ * Model B: $\frac{700\,kWh}{770\,kWh} \times 100 = 91\%$ * Model C: $\frac{600\,kWh}{630\,kWh} \times 100 = 95\%$ * Conclusion: Model C is the most energy efficient at $95\%$ .

Question: What is Alfred Wegener's theory?
Answer: That Earth's continents were once all connected in a giant landmass called Pangaea.
Question: What was Harry Hess's theory?
Answer: Seafloor spreading.
Question: What occurs along ocean ridges?
Answer: Volcanoes.
Question: List one piece of evidence for Wegener's theory.
Answer: Fossil twins.
Question: Why was Wegener's theory originally rejected?
Answer: Because he didn't have any explanation of how the movement was possible.
Question: What did Marie Tharp find?
Answer: She found the Mid-Ocean Ridge.
Question: How is sonar used?
Answer: By sending sound waves and waiting for them to bounce back; that helps to locate how far something is.