Pretest on prior knowledge CW credit Not for a grade, just to see what you already know Good Luck!
States of Matter ESSENTIAL QUESTIONS Compared to solids and liquids, what is unique about gases? How do substances change from one state to another? OBJECTIVES Recall properties on states of matter Explain why gases are easier to compress than solids or liquids Analyze and interpret a phase diagram
Chemcatalyst: __.__ Name some properties of solids: Can you give some examples of solids?
Solids Particles have fixed locations Packed tightly together in an orderly arrangement Vibrate in place
Properties of solids Not easily compressible Do not FLOW because they are packed tightly No effect with an increase of pressure
Think back… Which type of compounds are only solids at room temperature?? IONIC COMPOUNDS
Crystal Structure Orderly arranged particles in a pattern Also, known as a lattice A unit cell is the smallest part of a crystal that retains its shape
Allotrope A substance that exist in more than one form Carbon has 3 allotropes Graphite (in pencils) Diamonds (thanks Mr. Herman) Buckministerfullerene (C 60 )
Other Allotropes Oxygen O 2 or O 3 Phosphorus Red or white
Amorphous solids A solid that lacks order within its internal structure These solids are randomly arranged Example: Glass, plastic, synthetic fibers, rubber
Chemcatalyst :__.__ Why do you add salt to a pot of water?
Liquids Particles are spaced out more than solids Particles feel attraction between each other which keeps them close Less dense than solids
Properties of Liquids Take the shape of the container Definite volume Ability to flow (fluid) No effect with an increase of pressure
What’s a fluid? A continuous substance whose molecules move freely past one another and that has the tendency to assume the shape of its container
Boiling Point A liquid is heated to a temperature where the particles have enough kinetic energy to vaporize The liquid begins to bubble because the vapor is rising and escaping the container
Boiling Point (BP) At a particular temperature the vapor pressure is equal to the external pressure During the boiling process the temperature is constant Since, its based on pressure, not all liquids will boil at the same temperature
BP & Pressure Altitude will affect boiling points As you go up to higher altitudes, the pressure is lower; which in turn would lower the boiling point.
Think about this… Would the temperature at which water boils be higher or lower than 100 o C? Denver is 1600 m above sea level Water actually boils at 95 o C!!!
Kinetic energy and states of matter If Kinetic energy increases all particles begin to move faster and in turn change phase Kinetic energy is directly proportional to temperature
Did you know?! At higher altitudes, a pressure cooker is used so the vapor cannot escape and the food will cook more quickly! Due to the higher pressure, the more heat needed to have the water boil
Why do you add salt to a pot of water? By adding salt to your pot, it raises the BP to 102 o C, but salt water has a lower heat capacity than typical water. Needs less energy to heat the water What would be a more effective way to boil water, than salt? Think about pressure
Small scale Lab The behavior of liquids and solids
Chemcatalyst __. __ Explain the differences between a NaCl crystal compared to a piece of glass. What happens to kinetic energy when temperature decreases? If the pressure is lower, does boiling point change?
Gases Small, hard particles Empty space in between Particles are far apart
Gases Insignificant volume and no shape No attractive or repulsive forces between particles Move in straight lines until a collision Elastic collisions Flows like a fluid
Is a gas a fluid? Gases have the ability to flow because they can move past one another What happens over time as Bromine gas is left in the beaker?
Is there a difference between a gas and a vapor? At room temperature, a gas is a gas – Example: Chlorine gas (Cl 2 ), oxygen gas (O 2 ) At room temperature, a vapor is in some other form – Example: Water Vapor (H 2 O)
Gas Pressure Results from the force exerted by the gas on an object What is causing this force? The particles colliding with themselves and the object The force applied is very small for one, but imagine millions!!
Gas Pressure & a Vacuum A vacuum is where there are no particles, thus no pressure Space is a vacuum!
Think about this… Why can no one hear you scream in space? It’s a vacuum and sound needs a medium to travel
Measuring Pressure Barometer Used to measure atmospheric pressure Air pressure decreases as altitude increases
Chemcatalyst __.__ A.Solid B.Liquid C.Gas 1.Ability to flow and has a definite volume 2.An ordered pattern with particles in fixed positions 3.Particles have elastic collisions 4.Particles feel attraction between each other 5.Particles vibrate in place 6.Move in straight lines, until a collision Match the Property with the correct state of matter: B A C A or B A C
Changes of State A physical change occurs as a substance undergoes a change from solid liquid gas Energy is needed to complete this change
Solid Liquid Melting Particles within a solid gain enough energy to move into the liquid phase The organization of the particles break down Melting point (MP) the temperature at which it goes from solid liquid
Liquid Solid Freezing Lowers the energy or temperature where particles become more rigid in its shape Freezing Point (FP)- the temperature where a liquid begins to freeze
Did you know?! The melting point and the freezing point is the same EXACT temperature!!! Meaning solid and liquid are at equilibrium, until it shifts towards either one
Think back… Which one has a higher melting point? Salt or Sugar? (NaCl or C 12 H 22 O 11 ) Salt is an ionic compound, while sugar has weaker covalent bonds
Liquid Gas Evaporation Also, known as vaporization When liquid particles gain enough energy to leave the liquid phase and escape as a gas Since, the most energetic particles are leaving the leftover temperature decreases
Did you know?! Evaporation is a cooling process By sweating, your sweat is evaporated and in turn cooling down your body
Gas Liquid Condensation A loss of energy returns the gas to the liquid phase
Solid Gas Sublimation A solid skips the liquid phase and becomes a gas Occurs when the solid has a vapor pressure that is greater than atmospheric pressure at or near room temperature.
But doesn’t sub mean below? Sublimation is from the Latin word sublimare, which means to raise or elevate!!
Gas Solid Deposition Gas/vapor becomes a solid and skips the liquid phase Used for making computer chips and purifying mixtures!
Let’s make this concept map Solid Liquid Gas Melting Freezing Condensation Evaporation Sublimation Deposition
Answer the following in complete sentences: Is a phase change a chemical or physical change and explain why.
Chemcatalyst: __.__ Which change of state occurs when liquid becomes solid? Is there an increase or decrease of temperature/kinetic energy for this change? What happens to the particles during this change?
Phase Diagram A phase diagram shows the relationship between the 3 states Shows conditions (temperature & pressure) at which phases are at equilibrium
Phase diagram Let’s shade the 3 phases of our diagram
Phase Diagram Triple Point- where all 3 states exist at once Critical Point- no phase boundaries exist
Phase Diagram Each line represents an equilibrium between changes of states
Phase Diagram Normal means at standard pressure Or MP
Phase diagram Practice What temperature and pressure is the triple point? What temperature and pressure is the critical point? What temperature and pressure of the normal MP and BP?
Phase diagram Practice A. Pressure B. Temperature C. Triple point D. solid E. Liquid F. Gas/Vapor G. Critical Point H. Normal FP/MP I. Normal BP
Chemcatalyst __.__ A B G H F C Describe what’s happening:
Label and answer the following: 1.What state of matter would be at 75.0 Kpa and -120 o C? 2. What is the normal boiling point for Xe?