College Prep Chemistry Mr. Pompilii Ch 10: States of Matter College Prep Chemistry Mr. Pompilii

States of Matter 1. Solid 2. Liquids 3. Gases

Colloids: (Definition: when one type of substance is evenly dispersed in another) Ex) gas-liquids: foam, whipped cream Ex) liquid-liquid: milk, mayonnaise Ex) solid-liquid: blood, ink Ex) liquid-gas: fog, mist, clouds Ex) solid-gas: soot, smog Ex) gas-solid: Styrofoam, pumice Ex) liquid-solid: jelly, gelatin, jell-o

Gas dispersed throughout a liquid! That’s why it is light What is Shaving Cream? Gas dispersed throughout a liquid! That’s why it is light That’s why it’s form can change

Kinetic Theory: Kinetic Energy vs. Potential Energy Energy in motion, energy at work. Potential Energy: Stored Energy Energy with the capacity to do work

Chemical Kinetic or Chemical Potential???

Kinetic Theory All particles of matter are in constant motion – even the solids!

3- Assumptions about Gases from the Kinetic Theory 1. Gases are composed of tiny particles and mainly empty space 2. Gas particles move in rapid, constant, random motion 3. Collisions are perfectly elastic

Physical Properties of Gases: Volume: Shape Molecular Motion Density Intermolecular Forces: Avg. Kinetic Energy Indefinite Volume Indefinite Shape Constant and Random Relatively far apart None Constant: Elastic collisions

3- Variables that describe a Gas 1. Volume – measured in mL, L, or cm3 2. Temperature – measured in oC or K

3- Variables that describe a Gas: 3. Pressure – force acting on an object A push or a pull Atmospheric Pressure

Units that describe Pressure: SI Units: Pascal (Pa) are very small so we use kilopascal (kPa) 1000 Pa = 1 kPA 101.3 kPa = standard pressure

Other units that describe Pressure: 1 atmosphere (atm) Because there is 1 atmosphere’s worth of air above you at sea level 1 atm = 101.3 kPa mmHg (millimeters of mercury) 1 atm = 760 mmHg= 101.3 kPa Torr: 1 atm = 760 torr = 101.3 kPa

Converting Pressure Units 1 atm = 760 mm Hg = 760 torr = 101.3 kPa All units are equal to one another in these quantities!

Example Problem How many millimeters of mercury does a gas exert at 2.40 atm of pressure?

Example Problem Given: 2.40 atm Unknown: ? mm Hg Conversion Factor: 1 atm = 760 mm Hg Solve: 2.40 atm x 760 mm Hg/ 1atm = 1820 mm Hg

Device used to measure pressure Developed by Evangelista Torricelli Barometer Device used to measure pressure Developed by Evangelista Torricelli

Barometer at Sea Level

Sect. 10-2: Nature of Liquids

Sect. 10-2: Nature of Liquids Volume Shape Molecular Motion Density Intermolecular forces Avg. Kinetic Energy Definite volume Indefinite Shape Vibrate, flow and spin More Dense than gas Yes Lower than gas

Vaporization Definition: term used for the conversion of a liquid to a gas or vapor below its boiling point General term for the escape of molecules at the surface Can be an open or closed container

Evaporation – vaporization of an open container

Vaporization in a closed container: Vapor Pressure: vaporized particles collide with the walls of a sealed container, and create a pressure above the surface of the liquid. Some particles vaporize, others condense Ex) The “Sssst” in soda!

Dynamic Equilibrium Equilibrium reached between particles vaporizing and particles condensing

Boiling Boiling Point (bp): the temperature at which the vapor pressure of the liquid is just equal to the external pressure Bubbles form throughout the solution The vapor pressure inside these bubbles is equal to the atmospheric pressure Boiling and evaporation are cooling processes. Why?

Different from Boiling Point! Normal Boiling Point: the boiling point of a liquid at 1 atm lower pressures = lower boiling point not as much force holding particles in the solution higher pressure = higher boiling point more force on the surface of the liquid

Vapor Pressure

Distillation Apparatus

Distillation: A separation process Uses the specific boiling point of each liquid to separate a mixture of liquids Boiling point is a physical property and unique to each substance As a substance is boiling the temperature remains CONSTANT regardless of how much energy is added to the system

Sect. 10-3: Nature of Solids Volume Shape Molecular Motion Density Intermolecular forces Avg. Kinetic Energy Definite volume Definite Shape Vibrate on a fixed point More Dense than liquids Yes Lower than liquids

Solids – have repeating patterns called crystals

Crystal Structure & Crystalline Shapes

Allotropes– different forms of the same element Carbon Examples of Carbon allotropes: 1. Graphite 2. Diamond 3. Bucky Ball 4. Carbon- 540 5. Carbon – 70 6. Carbon- nanotubes

Graphite:

Diamond

Buckminsterfullerene: Buckyball Carbon - 60

Carbon-70 Another Fullerene Hollow ball Used for nanotechnology

Carbon- 540 Another Fullerene Hollow ball Used in nano- technology

Carbon- nanotubes Stronger than diamonds Good conductors of heat Can be used as conductors or semi- conductors

Amorphous Solids Lack ordered internal structure Ex) Rubber, plastic, asphalt, glass Glass: Supercooled Liquids

Melting Point Melting Point (mp): the temperature at which the solid turns into a liquid Melting points and freezing points are the same temperatures

Section 10.4 College Prep Chemistry Phase Changes Section 10.4 College Prep Chemistry

Summary of Phase Changes

Phase Diagrams: Shows the temperature and pressures at which a substance exists as a solid, liquid or gas. Triple Point: Point where all three curves meet Point at which all three phases exist in equilibrium Critical Point: Highest temperature and pressure at where a liquid and gas can coexist at equilibrium

Heat Curves: shows the temperatures at which phase changes occur

Heat Curve for Water:

Sublimation – solid phase to gas

Deposition – gas phase to solid