Physical Science Chapter 3 Solids, Liquids & Gases Physical Science Chapter 3

States of Matter Matter can exist in four states, or phases: Solid: definite shape and definite volume Liquid: no definite shape and a definite volume Gas: no definite shape or volume Plasma: very high energy, no definite shape or volume

Solids All solids have definite shapes and volumes. The particles that make up a solid are packed closely together so that they vibrate in place. The two types of solids are crystalline solids and amorphous solids.

Types of Solids Crystalline solids have an internal structure made of crystals. Crystals are regular, repeating patterns of arranged particles. An amorphous solid is a solid that flows very slowly over time and changes shape. Glass is an example of an amorphous solid.

Liquids Liquids have a definite volume, but not a definite shape. The particles in a liquid are close enough together that they cannot be compressed, but able to flow. Viscosity is the resistance of a liquid to flowing. Honey has high viscosity, while water has low viscosity.

Gases Gases do not have a definite shape or volume. Gas particles are much further apart and move very rapidly. Gas particles will expand to fill whatever container they are in. The behavior of gases is explained by their arrangement and movement.

Plasma The fourth phase of matter is called plasma. The plasma particles are very high energy. The plasma phase is rare on Earth, but is the most common phase in stars.

Phase Changes The amount of energy in particles is responsible for the different phases of matter. A solid substance tends to have less energy than a liquid of the same substance. Liquid substances tend to have less energy than gas substances. Phase changes can be caused by adding energy or taking it away.

The Phase Changes The phase changes are Melting: change from solid to liquid Freezing: change from liquid to solid Vaporization: change from liquid to gas Condensation: change from gas to liquid Sublimation: change from solid to gas

Melting Melting is the change in a substance from the solid state to the liquid state. Melting occurs when a substance absorbs energy. The melting point is the temperature at which melting occurs. The melting point can be used as a characteristic to identify an unknown substance.

Freezing Freezing occurs when a liquid substance becomes a solid substance because energy is lost. The freezing point is the temperature at which freezing occurs and is equal to the temperature of the melting point.

Vaporization The change of a substance from a liquid to a gas is called vaporization. Vaporization occurs when energy is absorbed. Evaporation occurs only at the surface of a liquid. Boiling is vaporization that occurs throughout a substance. The boiling point is the temperature at which boiling occurs. (when particles escape to the air from the liquid.

Condensation Condensation occurs when a gas becomes a liquid by losing energy. The condensation point is the temperature at which gas condenses and is equal to the temperature of the boiling point.

Sublimation Sublimation occurs when a solid goes directly to the gas phase without passing through the liquid phase. An example of a substance that sublimes is carbon dioxide. Dry ice (solid CO2) becomes a gas at room temperature.

Gases Gases are unique due to their changing properties of volume, temperature and pressure and can be described in terms of pressure, temperature and volume. To understand how a gas will behave in an experiment these three measurements need to be known: volume, temperature, and pressure.

Gas Volume The volume is the amount of space that matter occupies. Volume is measured in terms of cm3 or mL. The volume of a gas will always be the same as the container the gas is in. The gas particle will bounce off of each other and the walls of the container until they fill all the space.

Temperature Temperature is the measure of the average energy of the particles; resulting in random particle motion. As temperature increases, the gas particles will move faster and faster. At 20ºC (room temperature), gas particles move at approximately 500 m/s.

Pressure Pressure is the amount of force over a given area, or pressure = force/area. The pressure of a gas is the amount of force it is applying to the walls of the container. Pressure is measured in pascals, Pa or kilopascals kPa. Sometimes you’ll see the units as psi (pounds per square inch)

Gas Laws Boyle’s law states, “that pressure and volume of a gas are inversely related.”

Boyle’s Law Boyle’s law relates volume and pressure. Boyle’s law states that volume and pressure are inversely related when temperature remains constant. This means that if pressure increases, then volume decreases. Or, if pressure decreases then volume will increase, if the temperature stays the same.

Pressure and Temperature Pressure and temperature are directly related, if volume remains constant. This means that if temperature increases, then pressure increases. Or, if temperature decreases, then pressure decreases. This occurs because as temperature decreases, so does particle energy which means fewer collisions with the walls of the container.

Gas Laws Charles’ law states, “that if pressure of a gas is constant than, volume and temperature are directly related.”

Charles’ Law Charles’s law relates volume and temperature. Charles’ law states that if pressure remains constant, then volume increases directly with temperature. This means if temperature goes up, so does the volume of the gas. Or, if temperature goes down, so does the volume of the gas.