The way solids, liquids, and gases behave is very different because of how their tiny parts, called molecules, are arranged and how much energy they have.

Solids

• Shape and Volume: Solids keep their shape and have a fixed size.
• Molecular Arrangement: The molecules are packed closely together and stay in the same spot, often in a neat pattern.
• Movement: The molecules can wiggle a bit, but they don’t move around much.
• Density: Solids are usually heavy for their size. For example, plastics can weigh around 0.5 grams per cubic centimeter, while metals like gold can weigh over 19 grams per cubic centimeter.

Liquids

• Shape and Volume: Liquids have a set amount of space they take up, but they change shape to match their container.
• Molecular Arrangement: The molecules are a bit less packed than in solids and can slide past each other.
• Movement: The molecules can move around freely, which helps liquids flow.
• Density: Liquids are usually lighter than solids. For instance, water has a density of about 0.7 grams per cubic centimeter.

Gases

• Shape and Volume: Gases don’t have a fixed shape or size; they fill whatever space is available.
• Molecular Arrangement: The molecules in gases are spread far apart and are not arranged in any order.
• Movement: The molecules move quickly and can spread out, which makes gases easy to compress.
• Density: Gases are much lighter than liquids. For example, air at sea level weighs about 0.0012 grams per cubic centimeter.

In short, solids, liquids, and gases behave differently because of how their molecules are arranged, how they move, and how dense they are.