Do Now: What are some characteristics of a liquid and solid

Liquids in relation to gases According to the kinetic theory, both particles have kinetic energy This energy allows particles to flow past one another, allowing them to conform to the shape of the container These substances are known as fluids

Intermolecular attractions between the particles reduces the space between these particles, thus making liquids more dense than gases.

Solids Fixed volume and shape Although particles are arranged in orderly arrangements and fixed locations, their particles are still moving Most solids have crystalline structures

Crystal Particles that are arranged in an orderly, repeating 3-dimensional pattern (crystal lattice) Shape of a crystal reflects the arrangement of the particles within the solid

Unit Cell Unit cell- smallest group of particles within a crystal that retains its shape

Objective: To review different phase changes Do Now: Read the article about graphite and diamonds, and use the text to determine its similarities and differences. Be sure to cite from the article This will be a graded Do Now, so this must be done on a separate sheet of paper (40 point classwork)

Allotropes Solid substance that can exist in more than one form Carbon is the most common – Diamond – Graphite – Fullerene (buckminsterfullerene) Other elements that have allotropes – phosphorus, sulfur, oxygen, boron and antimony

Phase Changes

Gases and Liquid Phase changes Condensation- going from gas state to a liquid The phenomena that real gases undergo and not ideal This is due to gas particles attracting when they collide

Evaporation: going from a liquid to gas without applying heat During evaporation, only the molecules who achieve minimum kinetic energy escapes the liquid surface

Vapor Pressure A measure of force exerted by gas above its liquid is vapor pressure Vapor Pressure is effected by both temperature and the bond strengths of the liquid – Strong intermolecular forces have low vapor pressure – Weak intermolecular forces (nonpolar) have high vapor pressure

What makes a substance flammable? Flash point- the lowest temperature where there is enough vapor to be ignited vapor pressure and flash point are inversely proportional Gasoline has a flash point of -40 ◦ C Rubbing alcohol has a flash point of 11.7 ◦ C Water does not have a flash point

Boiling Point Going from liquid to gas when heat is applied When enough heat is applied to where all of the liquid has enough kinetic energy to vaporize, that’s when the liquid boils

Due to the fact that liquid boils when its vapor pressure is equal to external pressure, liquids to do not boil at the same temperature The lower the pressure, the lower the boiling point

Phase changes with Solids and Liquids Melting Point- when solid becomes a liquid When heat is applied, disruptive vibrations are strong enough to overcome the attractions that hold them in fixed positions

Freezing point- when a liquid becomes a solid Melting and freezing points are at the same temperature Ionic compounds have higher melting points because of their bond strengths, whereas covalent bonds have a relatively lower melting point because of their weaker bonds

Gas and Solid phase changes Deposition- where gas goes directly to solid Sublimation- where solid goes directly to gas Solids also have vapor pressure, and when the vapor pressure exceeds atmospheric pressure, sublimation occurs

Example of solids that sublime Carbon dioxide (dry ice) Iodine Air fresheners

Phase Change Diagram

Phase Diagrams

Triple Point Point on the phase diagram where the substance is at a solid, liquid and gas at the same time For water, when the temperature is at ◦ C and 0.61kPa, it is at triple point

Triple Point of water