The water molecule is very simple. A molecule is a piece of matter that contains two or more atoms. Atoms are the tiniest pieces of matter. The scientific name for water is H2O. It is called H2O because it has two atoms of hydrogen (H) and one atom of oxygen (O).
There are millions of these molecules in one drop of water. The form water takes depends on the movement of the water molecules. In liquid form, water molecules are constantly moving and rolling over themselves. You can pour liquid water into a container and it will move around to take the shape of that container. When water is frozen (ice) water molecules are locked into position and stay in that shape. When water boils, water molecules move very fast. Water molecules move so fast that they actually break apart from each other and escape into the air as water vapor or steam.
The two types of temperature scales are Fahrenheit and Celsius. The Fahrenheit scale is the one most commonly used in the United States. The Celsius scale is based on the metric system and is the one used in most other countries. However, the metric system is becoming more common in the USA. If you look at water temperatures, you can see how much easier the Celsius scale is to remember. Look at the following chart of water temperatures in the two different scales:
| Water | Fahrenheit | Celsius |
|---|---|---|
| Temperature | (• F) | (• C) |
| Boiling | 212• F | 100• C |
| Freezing | 32• F | 0• C |