Energy, Heat Transfer and Rocks: Year 8 Study Guide
Energy cannot be created or destroyed, but it changes form and moves from place to place.
Kinetic energy is the energy of motion and potential energy is stored energy, such as in a lifted object or a stretched spring. Other forms include heat, light, sound, chemical and electrical energy. The law of conservation of energy says that energy is transformed but never lost; however, some becomes heat that is hard to use. The unit is the joule (J).
Heat moves by conduction (through solids), convection (in fluids as warm parts rise) and radiation (waves that need no material). Conductors such as copper transfer heat well; insulators such as wool and air do not.
Energy transformations
| Device | Input | Useful output | Wasted |
|---|---|---|---|
| Torch | chemical (battery) | light | heat |
| Toaster | electrical | heat | light and sound |
| Hydro dam | gravitational potential | electrical | heat and sound |
| Solar panel | light | electrical | heat |
Heat transfer
Metal spoons get hot in soup (conduction). Hot air rises, which is why heaters are placed low and sea breezes form (convection). The Sun warms us through space (radiation). Dark surfaces absorb more radiation than light ones, and shiny surfaces reflect it, which is why a thermos is shiny inside. Insulation in roofs reduces heat loss by trapping air.
Safely, with supervision.
Pins fall off in order.
Particles pass on energy.
Wood conducts poorly.
The rock cycle
Rocks are recycled over millions of years. Igneous rocks (basalt, granite) form from cooled magma or lava. Sedimentary rocks (sandstone, limestone) form when sediments are compacted and cemented, and may contain fossils. Metamorphic rocks (marble, slate) form when heat and pressure change existing rock. Weathering, erosion, melting and uplift link them. Uluru is an arkose sandstone, and the Great Dividing Range contains a variety of rocks.
Worked example and common misconceptions
Example: A skateboarder at the top of a ramp has gravitational potential energy that becomes kinetic energy going down, with some lost as heat through friction. Common misconceptions: thinking energy is 'used up', that cold flows into objects and that rocks do not change. Draw energy flow diagrams (Sankey diagrams) to show the useful and wasted parts.
Check your understanding: model answers
1. Igneous, sedimentary and metamorphic. 2. Radiation. 3. Light energy changes into electrical energy.
✨ Key Takeaways
- Energy is conserved.
- Conduction, convection, radiation.
- Insulators reduce heat loss.
- Rocks are recycled in the rock cycle.
💬 Questions for Discussion & Reflection
- Name the three types of rock.
- Which method of heat transfer needs no material?
- What energy change happens in a solar panel?
Print a science experiment report →