Unit 4 AP Chemistry

Unit 4 Section 2 Modeling Phase Change & Comparing Compounds

Multiple Choice

PSI, torr, mmHG, atm all are units for....

• temp

• vol

• pressure

• weather

Fill in the Blank

1,976 torr is how many atmospheres? (atm)

Multiple Choice

At higher temperatures

• particles in an object have less energy

• particles in an object have more energy

• a gas contracts

• a.     particles in an object break apart.

Multiple Choice

As the particles increase in movement, they begin to _____ and move faster.

• move closer

• spread out

Match

Match the description to the correct particle motion

• The particle moves around an axis

• The particle stays in one place while moving

• The particle moves in space

Rotation

Vibration

Translation

• Rotation

• Vibration

• Translation

Lesson Objectives

• Summarize how variations in kinetic energy among particles results in changes in state

• Relate Intermolecular forces to the energy needed to change states of matter

• Differentiate between the properties of various types of solids

​Energy & Phase Changes

• Phase Change: the transformation from one state of matter to another

• Adding energy to a material increases the temperature of that material

  • At certain points, the temperature stops increasing​ while the substance changes state

    • Energy is used to either break or form intermolecular bonds

​Types of Phase Changes

• Some types of phase changes we experience on a daily basis

  • Solid → Liquid= Melting

  • Liquid → Solid= Freezing

  • Liquid → Gas= Vaporization

  • Gas → Liquid= Condensation

• Other types are less common in our everyday lives

  • Solid ​→Gas= Sublimation

  • Gas → Solid= Deposition

• The properties of a material can change at different states even if the particles are the same

​Heating a Liquid

• In the liquid state, particles have vibrational movement and rotational movement

  • still held together by intermolecular forces

• Heating a liquid adds energy to the particles, allowing them to break those forces holding them together and become a gas

• Boiling Point: the temperature at which intermolecular forces break in a liquid​

  • Can be predicted by looking at intermolecular forces

    • Stronger forces have higher boiling points

​Evaporation

• A liquid doesn't have to boil for vaporization to occur

• Every particle in a liquid has a different energy level

  • Below the boiling point, most particles do not have enough kinetic energy to vaporize into a gas, but a few do​

• Evaporation: The process by which particles at the surface of a liquid have enough energy to escape intermolecular forces​ and enter the gas phase

  • Increasing the temperature can increase the evaporation rate, even if it is not raised to the boiling point

Evaporation

​Condensation

• In the process of condensation, some particles have a lower energy level, that allows them to enter the liquid phase

• Cooling the temperature reduces the energy of particles, which allows particles to return to a liquid state​

​Vapor Pressure

• When Liquid is in a container, some particles will evaporate

• When those particles collide with the wall of the container, it produces pressure on the container

• Vapor Pressure: the pressure of gas above a liquid​

  • Vapor pressure leads to an equilibrium, where some particles evaporate while others condense

​Vapor Pressure and Boiling

• The boiling point is the temperature where the vapor pressure is equal to the external pressure on a fluid

• In a system of variable vapor pressure, different factors affect the boiling point of the liquid

  • At sea level, warmer temperatures are needed to reach the boiling point

    • At higher altitudes with lower pressure, liquids boil at a lower temperature

    • At higher pressures, liquids boil at higher temperatures

Multiple Choice

As the temperature of an object increases, the energy will increase at the exact same rate

• True

• False

Multiple Select

Select all that apply.

In the process of evaporation,

• particles at the surface that have enough energy can escape the liquid and enter the gas phase.

• some of the molecules in a gas will have lower energy than the rest and can transition to the liquid phase

• it happens at the surface of liquids and its one type of vaporization

• increasing the temperature of a liquid results in more particles having enough energy to evaporate

Multiple Choice

True or False: Increasing the temperature of a liquid results in more particles having enough energy to evaporate

• False

• True

​Heating a Solid

• particles in a solid have vibrational energy

• With enough energy, the particles can no longer contain it, and break free from each other

  • As they break free, they change to a liquid phase

• Melting Point: the temperature at which a solid becomes a liquid

​Sublimation

• Solids generally melt into a liquid at a gradual temperature change

• In some cases, solids change to the vapor state without passing through the liquid phase

• Sublimation: The change from a solid to a gas state

  • Occurs at STP with substances that have extremely weak intermolecular bonds

• Gives some solids vapor pressure

​Phase Diagrams

• Phase Diagram: a graph that describes the conditions of temperature and pressure at which a substance exists as a solid, liquid, or gas

  • Can show a triple point where all three states of matter can exist in equilibrium with each other.

Match

Match the phase change to it's name

• Condensation

• Vaporization

• Melting

• Freezing

Gas → liquid

Liquid → Gas

Solid → Liquid

Liquid → Solid

• Gas → liquid

• Liquid → Gas

• Solid → Liquid

• Liquid → Solid

Multiple Choice

Sublimation is the change of a

• Solid to a liquid

• Liquid to a solid

• Gas to a solid

• Solid to a Gas

• Gas to a Liquid

Multiple Choice

This image is called a

• Pressure map

• phase diagram

• transitional chart

• Melting table

Multiple Choice

Change of a gas directly into a solid

• Sublimation

• Condensation

• Evaporation

• Deposition

Multiple Choice

A gas...

• has a definite shape but no definite volume

• has a definite volume but no definite shape

• has fast-moving molecules

Multiple Choice

Which of the following terms identifies the change from a liquid to solid?

• Melting

• Condensation

• Vaporization

• Freezing

​Representative Units

• The Representative unit is the most basic form of a compound

  • A molecule is the representative unit of a covalent compound

  • An ionic compound is defined by a formula unit

    • Most basic ratio of ions in the compound

​Determining Compound Type

• Ionic compounds are made up of metals and non-metals

• Molecular compounds are made up of only non-metals

  • You can identify Molecular compounds based on the ​the elements

Multiple Choice

Is CaO an Ionic or Molecular Compound

• Ionic

• Molecular

Multiple Choice

Is CH₄ an Ionic or Molecular Compound

• Ionic

• Molecular

Multiple Choice

Is MgSO₄ an Ionic or Molecular Compound

• Ionic

• Molecular

​Covalent Network Solids

• Made up of networks of atoms or molecules held together by covalent bonds

  • Form complex 3-dimensional structures​

• Allotropes: different physical forms of the same element

  • Can have different properties b​ased on the number and arrangement of the atom

​Polymers

• Long repeating chains of molecules

  • Divided into smaller units called monomers​

  • Can be natural or synthetic

​Comparing Metal and Nonmetal

• Metals have too few electrons to form covalent bonds

  • What electrons they have don't stay close to the nucleus when they form ionic bonds​

​Crystalline Structures & Properties of Metals

• Pure metals are crystalline solids

  • Atoms are arranged in one of three repeating patterns​

    • Body-Centered Cubic (BCC)

    • Face-Centered Cubic (FCC)

    • Hexagonal Close-Packed (HCP)

  • The Pattern that atoms are arranged in determines the properties of metals

    • The closer electrons are, the easier it is for metals to be shaped

​Defects & Properties of Metals

• Crystal Dislocations

  • All crystals have some defects in their lattice structure

    • missing electrons, extra atoms, etc.

  • Point Defects: a defect or irregularity within a crystal that occurs at a point in the lattice

    • Three types

      • Interstitial: An extra atom is in a spot it doesn't belong

      • Substitution: A atom is in the wrong spot

      • Vacancy: An Atom is missing

    • Can change properties of the metal

      • Sapphires can change colors based on substitutions

​Dislocations

• Dislocations: Defects caused by entire planes of atoms being inserted or removed

  • Changes the properties of metals

    • More dislocations lower the malleability

  • Can be put into metals on purpose through Work Hardening

    • Bending or shaping a metal repeatedly, increasing the number of dislocations

    • Makes metals stronger, but more brittle

​Alloys

• Many metals are not pure metals

• Alloys: Mixtures of two or more elements, at least one of them a metal

  • Have Superior Properties

    • Steel has Carbon introduced to iron atoms

      • Carbon stops the iron from moving, making the alloy stronger than pure iron

Match

Match the point defect to its description

• Interstital

• Substitution

• Vacancy

An Extra atom is in a spot it doesn't belong

An atom is in the wrong spot

An atom is missing

• An Extra atom is in a spot it doesn't belong

• An atom is in the wrong spot

• An atom is missing