Matter is made of tiny particles called atoms and molecules, and it changes based on how these particles interact and move.
All matter on Earth, whether it's a solid chair, liquid water, or gaseous air, is fundamentally made of tiny particles called atoms and molecules. Atoms are the basic building blocks, and molecules are formed when two or more atoms join together. These tiny particles are constantly in motion, though their movement differs depending on the state of the matter.
The Building Blocks
- Atoms: The smallest unit of a chemical element. Think of them as the individual LEGO bricks.
- Molecules: Groups of two or more atoms held together by chemical bonds. These are like the different shapes you can build with LEGO bricks.
How Does Matter Exist? States of Matter
Matter typically exists in one of three main states on Earth: solid, liquid, or gas. The state depends on how the atoms or molecules are arranged and how much energy they have, which affects their attraction to each other and their movement.
Here's a quick look at the states:
| State | Particle Arrangement | Particle Movement |
|---|---|---|
| Solid | Closely packed, fixed positions | Vibrate in place but don't move past each other. |
| Liquid | Closely packed, no fixed shape | Can move past each other, flow. |
| Gas | Far apart, no fixed shape/volume | Move freely and randomly at high speeds. |
As the reference states, in a solid, the particles are very attracted to each other. They are close together and vibrate in position but don't move past one another, giving solids a definite shape and volume.
How Does Matter Change? State Changes
Matter changes its state primarily through the addition or removal of energy, usually in the form of heat. Adding heat makes the particles move faster, while removing heat slows them down.
Here are the common ways matter changes state:
- Melting: Solid changes to liquid (e.g., ice -> water). This happens when a solid gains enough energy to overcome the strong attractions holding particles in fixed positions.
- Freezing: Liquid changes to solid (e.g., water -> ice). This is the reverse of melting; particles lose energy and settle into fixed positions.
- Boiling/Evaporation: Liquid changes to gas (e.g., water -> steam). Particles gain enough energy to break free from the liquid surface and move far apart.
- Condensation: Gas changes to liquid (e.g., steam -> water droplets). Particles lose energy and come closer together.
- Sublimation: Solid changes directly to gas (e.g., dry ice -> carbon dioxide gas). Particles gain enough energy to skip the liquid state.
- Deposition: Gas changes directly to solid (e.g., water vapor -> frost). Particles lose energy and skip the liquid state.
These changes are physical changes, meaning the substance itself remains the same (water is still H₂O whether it's ice, liquid water, or steam); only its form changes.
Understanding how matter is composed of atoms and molecules and how their behavior changes with energy helps explain everything from why ice melts in the sun to how steam powers engines.
