Phases of matter

• Solid phase


  Molecules are closely bound to one another by molecular forces
• A solid holds its shape
• The volume of a solid is fixed by the shape of the solid
• Liquid phase


  Molecular forces are weaker than in a solid
• A liquid will take the shape of its container
• A liquid has a free surface in a gravitational field
• In microgravity, a liquid forms a ball inside a free surface
• Regardless of gravity, a liquid has a fixed volume
• Gas phase


  Molecular forces are very weak
• A gas fills its container
• A gas takes both the shape and the volume of the container