Energy transfers and transformations occur all around us. Chemical energy in food is transformed into kinetic energy when we move and heat energy to keep us warm. Energy transformations have also changed how cities function over time. Buildings now use electricity for lighting rather than candles or gas lamps, and transportation is powered by gasoline and diesel engines rather than horse-drawn carriages. Diagrams can be used to represent energy transfers, such as Sankey diagrams that show the amounts of different forms of energy using different width arrows.

1. Energy transfers
Chapter 16
Physics

2. Energy transfers and transformations
We are living at this moment due to the energy
transfers in our body.
As energy is transferred, it is transformed (changed).
Chemical energy in the food is transformed to
movement (kinetic) energy when you raise your hand.
Chemical energy is also transformed into heat energy
to keep you warm.

4. A city in the past
• Buildings were lit by candles, oil lamps
and gas lights.
• To keep the building warm they used
coal and wood.
• Streets were lit by gas lights
• Transportation was by carriages and
carts
• Trains are pulled by steam locomotives
• People walked
A city today
• Buildings are lit by electricity
• Buildings are warmed by heaters and
cooled by air conditioning powered by
electricity.
• Transportation is by cars, vans and trucks
powered by petrol or diesel engines
• Trains are pulled by a locomotive with an
electric motor.
• People use aircraft, uses fuel called
kerosene (petrol)

5. Stored chemical
energy
Catapult Kinetic energyStrain energy
Light and heat
energy
Bunsen burner
a) Releasing a catapult
b) Burning gas in a Bunsen burner
Energy input Energy converter Energy output
Energy transfer diagrams

6. Light energy
Balloon strain energyKinetic energy
Chemical energyCamera
c) Blowing up a balloon
d) Taking a photograph

7. Sankey diagrams
A second kind of diagram that shows
energy changes.
It shows arrows of different widths.
The width of the arrow represents the
amount of energy.
The unit of energy and work is the
Joule (J).
A thousand Joule (1000 J) = 1 kJ
(kilojoule)

8. A car engine has an energy input of 200kJ. The energy output is 80kJ
of kinetic energy and 120kJ of heat energy.
Energy in a car engine

9. -When a seed germinates, the
tip of the root pops out.
(Energy stored inside the
seed is used)
-Some of the light energy
falling on the leaves is
trapped.
- It is converted into chemical
energy as the plant makes
food (Photosynthesis).
Plants and energy

10. - The herbivore animals then has a store of chemical energy, which
it uses to keep itself alive and to move about.
- Carnivore animals feed on herbivorous animals and take in stored
chemical energy.
The chemical energy stored in
plants is transferred to a
herbivorous animal when it eats it.

11. - If you do not take care while barbecuing the meat will
catch fire.
- The meat and fat burn because they contain chemical
energy (all food do).
- Energy in food is released through respiration process.

12. The chemical energy in food is released in a process
called respiration

13. Power station generator

14. Electrical energy
(produced)
Heat energy
(Heats the
water)
Kinetic
energy
(Water to gas)
Chemical
energy
(Coal)
Kinetic energy
(gas moves turbine)
Energy transfers in a power station
Burn it

15. Law of conservation of energy
Energy cannot be made or
destroyed, it can only be
changed from one form to
another.