# Energy REvision map

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• Created by: DGL
• Created on: 28-03-21 20:34
• Energy
• Energy and temperature
• Temperature is measured in degrees Celsius (°C).
• Internal (thermal) energy is measured in joules (J).
• The amount of thermal energy stored in something depends on:
• ?      how hot it is (its temperature)
• ?      the material it is made from
• ?      its mass.
• When two objects are at different temperatures, energy will be transferred from the hotter one to the cooler one until they are at the same temperature.
• Transferring energy by heating
• Energy can be transferred by heating in different ways.
• Evaporation  can take place from a liquid at any temperature.
• When part of a liquid evaporates, it is the fastest-moving particles that escape to form a gas.
• The particles that are left are storing less energy as movement and so the temperature of the remaining liquid is lower.
• Conduction takes place in solids and can also happen in liquids (although not very well).
• The particles in a solid are held together tightly.
• When they gain energy they vibrate faster and further, and the vibrations are passed on.
• Metals are the best conductors.
• Most other solids are poor conductors.
• Convection takes place in fluids (liquids and gases).
• When part of a fluid is heated, the particles spread further apart and the fluid becomes less dense.
• This makes it rise. As it rises it meets cooler fluid and passes the energy on. More cool fluid moves in to replace the rising fluid, setting up a convection current.
• Infrared radiation can transfer energy through empty space and also through transparent materials.
• Any hot or warm object gives off or emits radiation.
• When something takes in energy from radiation, it is said to absorb it.
• Power
• Power is the rate at which energy is transferred.
• Power is measured in watts (W) or kilowatts (kW).
• Efficiency
• Not all energy is transferred usefully. Wasted energy is often transferred by heating. The percentage of useful energy produced by something is known as its efficiency.
• Sankey diagrams shows the energy transfers
• The width of each arrow shows the amount of energy it represents.

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