Changes in energy

Part 1 of 8Stored energy and change

• Stored energywhen energy is stored, it is not doing anything
• Before changeenergy must be stored before it can be changed or transferred
• Useful changesenergy is changed in a way that we want

Part 2 of 8Process and event

• Processsomething such as burning that changes or transfers energy
• Eventsomething that happens, such as a book falling from a shelf
• Burningit changes chemical energy stored in a fuel to thermal energy

Part 3 of 8Diagrams of energy changes

• Arrowsan arrow from one energy to another represents a change in energy
• Fire burning woodchemical → thermal
• Televisionelectrical → sound and light
• Book falling from a shelfgravitational potential → kinetic
• Candlechemical → light
• Ball rolling down a hillgravitational potential → kinetic

Part 4 of 8Everyday examples

• Cooking pot on a wood firechemical energy in the wood changes to thermal energy, which is transferred to the pot and food
• Walking up stairschemical energy from food changes to kinetic energy, then to gravitational potential energy as the person rises
• Gas power stationchemical → thermal → kinetic → electrical

Part 5 of 8Power station sequence

1. Natural gas stores chemical energy.
2. Burning the gas changes the chemical energy to thermal energy.
3. The thermal energy is changed to kinetic energy in large spinning generators.
4. The kinetic energy is changed to electrical energy.
5. The electrical energy is transferred through wires to homes and buildings.

Part 6 of 8Harmful energy changes

• Dangerous changestyphoons, hurricanes, earthquakes and tsunamis are energy changes that can be very dangerous
• Damagestrong wind transfers energy in a damaging way
• Not all usefulsome energy changes are not useful, which is covered in the next topic

Part 7 of 8Investigating candle energy

1. Measure and record the starting temperature of cooking oil in a beaker or metal can on a tripod and gauze.
2. Light the candle, place it under the beaker and start the timer.
3. Stir the oil at regular intervals with a stirring rod, not with the thermometer.
4. Record the temperature every minute together with the time.
5. Stop heating when the temperature has risen by 10 °C and blow out the candle.
6. Show the results in a table and plot a line graph with temperature on the vertical axis.

Part 8 of 8Results of the candle investigation

• Energy sourcethe chemical energy stored in the candle changes to thermal energy
• Not all heats the oilsome thermal energy also heats the air, the beaker and the equipment
• Better transferplacing the candle closer or using a lid or draught shield transfers more energy to the oil
• Graph typea line graph shows the trend of temperature against time better than a bar chart