States of Matter What are the three main states of matter? Solid, liquid, and gas The Kinetic theory is used to explain the different states of matter. According to the kinetic theory all matter is made up of tiny little particles called atoms and molecules. Atoms and molecules are in constant motion and are continually bumping into each other.

The state of matter depends on how fast the particles move and how much they are attracted to each other.

Solids: Liquids: Gases: Have a definite shape and volume The particles are strongly attracted to each other and vibrate in place Liquids: Change shape but not volume The particles have enough energy to slide past each other and take the shape of their container Gases: No definite shape or volume Exert pressure on the inside of their container

The Nature of Gases Kinetic Theory The particle are hard spheres with an insignificant volume therefore they take the volume of their container. The motion is constant and random The motion of a particle is unaffected unless the particle collides Forces of attraction can be ignored under ordinary conditions

Gas Pressure Pressure is a result of the collisions of gas particles with an object. A Barometer is used to measure atmospheric pressure. (or you can google it with your smartphone) 1 atm = 760 mm Hg = 101.3 kPa = 760 torr These measurement are all what we call standard pressure.

Gas Pressure What is the pressure in atm and mm Hg if a pressure gage reads 450 kPa?

Properties of Gases Compressibility is how much the volume decreases under pressure. Factors affecting gas pressure Amount Volume Temperature

Amount of Gas

Volume of Gas

Temperature of Gas

Boyle’s Law If temperature is constant, as the pressure of a gas increases, the volume decreases.

Boyle’s Law A balloon contains 30.0 L of He at 103 kPa. What is the volume of the helium when the balloon rises to an altitude where the pressure is only 25.0 kPa?

Charles’s Law If the pressure is constant, as the temperature (in Kelvin) of an enclosed gas increases, the volume increases.

Charles’s Law A balloon inflated in a room at 24.0°C has a volume of 4.00 L. The balloon is then heated to a temperature of 58.0°C . What is the new volume if the pressure remains constant?

Combined Gas Law The volume of a gas filled balloon is 30.0 L at 313K and 153 kPa pressure. What would the volume be at STP?

Changes of State A change of state is the conversion of a substance from one physical form to another. All changes of state require a change in the amount of energy. What happens when energy is added? Particles move faster and spread apart What happens when energy is removed? Particles move slower and get closer together.

Melting: a solid changes into a liquid. Melting point is the temperature at which a substance changes from a solid to a liquid. Most substances have a unique melting point that can be used to identify them. Energy is absorbed by a substance in order to overcome the attractions between particles. Freezing: a liquid changes into a solid Freezing point is the temperature at which a substance changes from a liquid to a solid. Freezing is the reverse process of melting so they occur at the same temperature. Energy is removed causing the particles to slow down and lock into place.

Vaporization: a liquid changes into a gas Boiling occurs throughout a liquid while evaporation occurs at only the surface of the liquid. The boiling point is the temperature at which a liquid rapidly turns into a gas. Boiling point is affected by pressure: lower pressure produce lower boiling points. Energy is added causing the particle to spread further apart and escape into the gas phase.

Condensation: a gas changes into a liquid The condensation point is the temperature at which a gas becomes a liquid and is the same as the boiling point. Energy is removed causing the particles to slow down and clump together. Sublimation: solids change directly into a gas Dry Ice is an example of a substance that changes directly from a solid to a gas.

Condensation Freezing Vaporization Melting During a Phase Change the temperature remains constant and does not change. As energy is added the particles in matter move faster and spread apart.

Exothermic or Endothermic Comparing changes of state If energy is being added the change of state is considered to be endothermic. If energy is being removed the change of state is considered to be exothermic. Change of State Direction Heat Goes Exothermic or Endothermic Melting Freezing Vaporization Condensation Sublimation

Phase Diagram The triple point is the set of conditions when all three phases can exist in equilibrium with each other.