States of Matter

States of Matter: Solids, Liquids, and Gases

Solids

  • Fixed volume and shape; high density.

  • Atoms vibrate in position but do not change location.

  • Particles are closely packed in a fixed and regular pattern.

Liquids

  • Fixed volume but adopts the shape of the container.

  • Generally less dense than solids (water is an exception) but much denser than gases.

  • Particles move and slide past each other, allowing liquids to adopt the container's shape and flow freely.

Gases

  • No fixed volume; takes up the shape of the container.

  • Very low density.

  • Can be compressed into a smaller volume due to large spaces between particles.

  • Particles are far apart and move randomly and quickly (around 500 {m/s}) in all directions.

  • Particles collide with each other and the sides of the container, creating pressure.

Particles in a Solid

  • Arrangement:

    • Regular repeating pattern.

    • Close together, touching each other.

  • Movement:

    • Vibrate about fixed positions; do not move apart.

  • Forces between particles:

    • Stronger than in a liquid.

  • Shape:

    • Fixed shape and volume.

Particles in a Liquid

  • Arrangement:

    • Irregular.

    • Close together, touching each other.

  • Movement:

    • Move around and slide past one another.

  • Forces between particles:

    • Not as strong as in a solid.

  • Shape:

    • No fixed shape (takes the shape of the container) but fixed volume.

Particles in a Gas

  • Arrangement:

    • Irregular.

    • Far apart.

  • Movement:

    • Move freely and collide with each other.

  • Forces between particles:

    • Non-existent.

  • Shape:

    • No fixed shape or volume.

Summary of Properties

State

Density

Arrangement of particles

Movement of particles

Energy of particles

Solid

High

Regular pattern

Vibrate around a fixed position

Low energy

Liquid

Medium

Randomly arranged

Move around each other

Greater energy

Gas

Low

Randomly arranged

Move quickly in all directions

Highest energy

Interconversion Between the Three States of Matter

Interconversion Names & Definitions

  • Melting: Conversion from solid to liquid due to increased temperature.

    • Melting point: Temperature at which a solid starts to melt (e.g., ice melts at 0^ {o}C).

  • Boiling: Conversion from liquid to gas due to increased temperature; also known as vaporization.

    • Boiling point: Temperature at which a liquid starts to boil (e.g., water boils at 100^ {o}C).

  • Condensation: Process by which a gas turns to liquid.

  • Sublimation: Process by which a solid turns directly to gas without melting.

  • Solidification: Process by which a liquid turns to solid (freezing).

  • Evaporation: Process by which a liquid turns to a gas below its boiling point.

  • Volatile liquids: Liquids that evaporate at room temperature.

Evaporation

  • Occurs when a liquid changes into a gas over a range of temperatures.

  • Occurs only at the surface of liquids where high-energy particles can escape at temperatures below the boiling point.

  • A larger surface area and warmer liquid surface allow for quicker evaporation.

Condensation

  • Occurs when a gas changes into a liquid upon cooling over a range of temperatures.

  • As a gas cools, particles lose energy and group together to form a liquid.

Sublimation

  • Occurs when a solid changes directly into a gas.

  • Happens to a few solids, such as iodine or solid carbon dioxide.

  • The reverse reaction is called desublimation or deposition.

State Changes & Kinetic Theory

  • When substances are heated, particles absorb thermal energy, which is converted into kinetic energy.

  • Heating a solid causes its particles to vibrate more; as temperature increases, they vibrate so much that the solid expands until the structure breaks and melts.

  • On further heating, the now liquid substance expands more, and some particles at the surface gain sufficient energy to overcome intermolecular forces and evaporate.

  • When the boiling point temperature is reached, all the particles gain enough energy to escape, and the liquid boils.

  • These changes in state can be shown on a graph called a heating curve.

  • Cooling down a gas has the reverse effect; this is shown on a cooling curve.

  • The horizontal sections on heating/cooling curves occur during a change of state when there is no change in temperature.

Heating and Cooling Curves

  • Heating curves show the states, state changes, and temperature changes as time progresses during heating.

  • Cooling curves are the mirror image of heating curves.

  • During a state change, there is no temperature change.

Pressure & Temperature in Gases

  • A change in temperature or pressure affects the volume of gases.

  • As the air inside a hot air balloon is heated, it expands, and the balloon gets bigger because the volume of a gas increases as its temperature increases.

  • If a gas is stored inside a container that is squeezed, the pressure increases as the volume decreases like in a bicycle pump.

Gases & Kinetic Theory

  • Gaseous particles are in constant and random motion.

  • The pressure that gas creates inside a closed container is produced by the gaseous particles hitting the inside walls of the container.

  • An increase in temperature increases the kinetic energy of each particle, as heat energy is transformed to kinetic energy, so they move faster.

  • As the temperature increases, the particles in the gas move faster, impacting the container's walls more frequently.

  • If the container walls are flexible and stretchy, then the container will get bigger, like a hot air balloon.

  • If the container is made smaller, then the gas particles hit the wall more frequently.

  • A decrease in volume causes an increase in gas pressure.