Here's why:
* Atoms are the building blocks of everything: Atoms are the smallest unit of an element that retains the chemical properties of that element.
* Solids have a fixed shape and volume: This is because the atoms in a solid are closely packed together and held in a rigid structure by strong attractive forces. The atoms vibrate in place but don't move freely like in liquids or gases.
Examples:
* A piece of metal: Made up of a lattice of metal atoms.
* A rock: Made up of a mixture of different minerals, which themselves are made up of atoms.
* Ice: Made up of water molecules (which are themselves made of hydrogen and oxygen atoms).
Important Note: While we often talk about solids being made of atoms, it's more accurate to say they are made of molecules, which are groups of two or more atoms held together by chemical bonds. However, even molecules are still composed of individual atoms.
