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Science
Wheel
Think about all the things that use wheels. Cars and trucks have wheels. Rollerblades have wheels. Bicycles have wheels. Shopping carts and suitcases have wheels. The wheel is one of the most important inventions in history.
WHAT ARE WHEELS?
Wheels are round. Wheels can be solid disks. Or they can be round hoops with spokes to make them stronger, like bicycle wheels.
Atoms
An atom is a tiny, tiny bit of matter. It’s really hard to imagine how small an atom is. Suppose you could line atoms up in row. It would take 100 million atoms to make a row only 1 centimeter long.
Everything in the world is made of atoms. The chair you are sitting on, the computer you are looking at, the clothes you are wearing, and even your body are all made of atoms.
There are more than 100 kinds of atoms. Each kind of atom belongs to a different element, such as oxygen or iron.
Chemical Reactions
Make both of your hands into fists. Put your closed fists together then pull them apart. Nothing holds your hands together, so it’s easy to pull them apart.
Now link your fingers together. Curl them around one another and pull. It’s hard to pull your hands apart. Linking your fingers is like a chemical reaction.
MIXING CHEMICALS
A chemical reaction can happen when you mix two or more chemical elements together. A chemical element is made of only one kind of atom. There are more than 100 different kinds of atoms. Atoms are much too small to see.
Chemical Elements
You and everything around you are made of chemical elements. The elements are sort of like LEGO or Tinkertoy pieces. You can put LEGO or Tinkertoy pieces together to make new things. You can take an object built of LEGO or Tinkertoy pieces apart. When there is nothing more to take apart, you have a pile of LEGO or Tinkertoy pieces. The pieces are different from the original object. You cannot take apart a LEGO or Tinkertoy piece without breaking it.
Materials, or substances, that you cannot take apart are called elements. Elements can link together to make all kinds of materials. The elements oxygen and hydrogen, for instance, together make water. Oxygen and the element carbon together make carbon dioxide, a gas that plants need.
Color
The world is full of beautiful color. You see a violet dress, a blue car, a yellow flower, and a green tree. The colored leaves on trees in autumn mean that winter is coming. All kinds of colors are everywhere.
COLOR COMES FROM LIGHT
White light, including sunlight and light from a light bulb, is actually made of all the colors of the rainbow. Have you ever seen sunlight that hits a piece of crystal?