W is for WATER matter: any material or
substance that takes up space.
How many atoms do you think are in a glass of water? The exact number is hard to figure out. Imagine counting all the stars in the universe. That would be an enormous number! Well, a glass of water has more atoms in it than the universe has stars! Atomazing!
atom: the smallest particle of
matter.
hydrogen: the most common element in the universe, and one of the elements of water. oxygen: an element that is a gas in the air. People and animals need oxygen to live. element: a substance that
contains only one kind of atom.
WATER MAGIC
There is nothing in the word like water. Water is odorless, tasteless, and colorless—and it’s the most important substance on Earth. All living things need water to live.
WORDS
TO
KNOW
DID YOU KNOW? The word hydrologist comes from the ancient Greek words hydro for “water” and logos for “study.”
Water exists in three different forms—solid, liquid, and gas. Water can transform from one form to another and then back again. It’s like magic!
WATER MOLECULE CHEER When atoms join, they form molecules. A water molecule is made of three atoms. And what are those three atoms? Give me an H! . . . Give me a 2! . . . Give me an O! What does that spell? . . . H2O! H stands for hydrogen. The number 2 means there are two hydrogen atoms. O stands for oxygen. Hydrogen and oxygen are two elements.
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