Monday
Monday: What Is Water Made Of?
Rocket tips a bag of dry beans onto the Bench. Big white beans and small red beans roll everywhere.
"Atoms," he says. "Pretend atoms. I want to build water."
Raven catches a red bean before it rolls off the edge. "What do you notice? Two sizes. Maybe two kinds of atoms."
Nova hovers over the pile, her light making the beans gleam. "Water is a team of three," she says. "But not three of the same."
"Two of one and one of another," Rocket says. He lines up two small red beans beside one big white bean.
"Two hydrogen and one oxygen," Raven reads from the Bench Log. "H2O. Rocket, you just built a molecule."
Rocket stares at his three beans. "Every drop of water is made of these?" Nova hums. "Trillions of them."
Atoms are the building blocks
All matter is made from atoms. Atoms are the building blocks of matter.
An atom is the smallest particle of an element that still has the element's properties. Atoms are extremely small, far smaller than a billionth of a meter across.
An element is the simplest form of matter that has a unique set of properties. It cannot be broken down into different kinds of substances.
As of 2010 there were 118 known elements. Ninety-eight of them occur naturally on Earth. Hydrogen, oxygen, carbon, sodium and chlorine are five of them.
Each element has its own kind of atom. Every hydrogen atom has one proton in its center. Every oxygen atom has eight.
- Read the question.
- Tap your answer.
Atoms team up into molecules
Individual atoms can combine with other atoms to form molecules. Molecules range in size from two atoms to thousands of atoms.
A water molecule contains two atoms of hydrogen and one atom of oxygen. Chemists write it as H2O.
The oxygen and nitrogen in the air occur as two-atom molecules. Each oxygen molecule is two oxygen atoms joined together.
A molecule of water vapor has the same composition, H2O, as a molecule of liquid water or ice. Changing state does not change the molecule.
| Substance | Atoms in one molecule | Formula |
|---|---|---|
| Water | 2 hydrogen, 1 oxygen | H2O |
| Oxygen gas | 2 oxygen | O2 |
| Carbon dioxide | 1 carbon, 2 oxygen | CO2 |
| Statement | True or false? |
|---|---|
| All matter is made from atoms. | ? |
| A molecule is a single atom. | ? |
| Oxygen in the air is found as two-atom molecules. | ? |
| Ice and water vapor have different molecules. | ? |
- Tap a card.
- Then tap its spot.
Build one water molecule: two of one kind and one of the other. Then build three more.
Count all your atoms. Four molecules of water use how many atoms in total? Write it in your Bench Log.
Keep small objects away from younger children and pets. Nothing goes in anyone's mouth.
The atom and molecule facts come from NASA, the U.S. Geological Survey and a chemistry text hosted by the University of California, Davis.
Great building. Tomorrow you will learn to read a formula like a recipe, including the tiny numbers.