Tiny Building Blocks

Why it matters

Imagine zooming into a grain of salt until you reach the tiniest building blocks of matter — atoms. Atoms rarely stay alone: they join together into molecules, the particles that make up the substances all around you.

Predict first

If you keep breaking a piece of chalk into smaller and smaller pieces, what is the smallest unit that still retains the properties of chalk?

Atoms combine to form molecules. A molecule is the smallest particle of a substance that has all of the physical and chemical properties of that substance.

• A molecule — correct
• An atom
• A subatomic particle
• Nothing, it disappears

What you do

Sort each particle: is it a single atom, or a molecule (two or more atoms joined together)?

Check yourself

Which statement best describes the relationship between atoms and molecules?

Atoms are the basic units. When two or more atoms bond together, they form a molecule.

Why can't we see atoms with a normal microscope?

Atoms are incredibly tiny, typically around 0.1 to 0.5 nanometers in diameter, far below the resolution limit of visible light microscopes.

In the formula H₂O, what does the '2' indicate?

Subscripts in a chemical formula indicate the number of atoms of the element immediately preceding it. H₂ means two hydrogen atoms.

• Atoms are made of molecules
• Molecules are made of atoms — correct
• Atoms and molecules are the same thing
• Molecules are smaller than atoms
• They are too small — correct
• They are invisible ghosts
• Microscopes only see liquids
• Atoms move too fast to be seen
• Two oxygen atoms
• Two hydrogen atoms — correct
• Two water molecules
• The charge of the molecule