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Junior School: States of Matter

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Solids, liquids and gases - BBC Bitesize


A solid has definite volume and shape, a liquid has a definite volume but no definite shape, and a gas has neither a definite volume nor shape.



What Is a Solid? Definition and Properties

A solid is defined as a state of matter with a definite shape and volume. In contrast, liquids can change shapes, while gases can change both shape and volume. The particles in a solid (atoms, molecules, ions) are tightly-packed compared to liquids and gases. The arrangement may be a regular lattice called a crystal or an irregular arrangement called an amorphous solid.

Properties of Solids

Properties of solids include:

  • Particles are packed closely together. This allows atoms and molecules to form chemical bonds.
  • Solids are rigid.
  • Solids don’t flow.
  • Solids aren’t readily compressible.

Examples of Solids

Anything with a fixed shape and volume is an example of a solid. Examples of solids include:

  • Most metals (coins, tools, cutlery, nails)
  • Building materials (bricks, wood, glass, concrete)
  • Everyday objects (pots and pans, desk, toys, computer, automobile)
  • Rocks and minerals
  • Gems and most crystals (diamond, sapphire, ruby)
  • Ice
  • Most chemical elements (exceptions include many nonmetals)

Examples of things that are not solids include air, water, liquid crystals, the elements mercury and helium, and steam.


Examples of Liquids

liquid is a state of matter that has a definite volume, but no fixed shape. In other words, a liquid takes the shape of its container. Liquids consist of atoms or molecules that are loosely connected by intermolecular bonds. In contrast, the atoms or molecules in a solid are fixed in a rigid shape, while the particles in a gas are separated by great distances. Most liquids resist compression. Liquids have surface tension, so they can wet surfaces.

Examples of Liquids

Here are examples of liquids at room temperature and pressure.

  • Water
  • Oil
  • Blood
  • Mercury
  • Milk
  • Coffee
  • Vinegar
  • Gasoline
  • Soft drinks
  • Juice
  • Alcohol
  • Liquid dishwashing detergent
  • Magma
  • Household bleach
  • Bromine
  • Acetone
  • Honey

Properties of Liquids

Liquids share common properties.

  • Liquids take the shape of their container. Particles within a liquid can move. Liquids share this property with gases.
  • Liquid flow when poured.
  • Liquids have a relatively fixed volume. Changing the temperature or pressure of a liquid does slightly alter its volume.
  • Liquids can wet surfaces.
  • Most liquids are difficult to compress. Liquids share this property with solids.
  • Liquids have a higher thermal conductivity than gases. In other words, they absorb heat better than gases.
  • At the right combination of temperature and pressure, liquids become solids or gases.