1.What Makes a Rainbow？ 2.How Volcanoes Blow Off Steam 3.Spring: Nature Awakens 4.Winter: Nature Asleep 5.Moon Phases 6.Space Stations：Stepping Stones into Space 7.Not Your Average House Cat 8.Natures Eavesdroppers 9.How Horses Sleep 10.Songbirds All Year 11.Beautiful Bowers 12.How Bees Make Honey 13.Wind Power 14.Ice Racing 15.To the Point 16.Up High with Hydraulics 17.Start Your Engine 18.Magnets Attract， Magnets Repel
內容試閱：
Start Your Engine
Page 2
What makes a car go?
Page 3
Most cars run on gas. A car is always moving， so it has to carry its energy source with it. That’s why cars have big tanks that we fill with gas.
Page 4
The engine burns the gas.
Page 5
Inside the engine， small gas explosions push pistons. The pistons turn a shaft. Then the shaft turns the wheels. This makes the car move!
Page 6
Some cars run on electricity instead of gas. Batteries store the electricity.
Page 7
Electric motors do not have pistons. Electric motors have magnets and coils of wire. Electricity moves through the coils. Then the coils become magnets. The magnetic parts push and pull at one another. The shaft spins and turns the car’s wheels.
Page 8
Do you see the orange box under the car seats? It holds the batteries.
Page 9
Batteries need to be recharged. Drivers go to electric charging stations to plug in the car!
Page 10
Batteries are heavy. They do not hold as much energy as gasoline.
Batteries must be replaced when they wear out.
Page 11
Scientists are learning how to make lighter， stronger batteries. Scientists also look for ways to recycle batteries. How will cars of the future run?
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