PDF Chapter 5 Lecture Notes: Solids, Liquids, and Gases

Chemistry 108 lecture notes Chapter 5: Solids, Liquids, Gases

Chapter 5 Lecture Notes: Solids, Liquids, and Gases

Chapter 5 Educational Goals 1. Define, compare, and contrast the terms specific heat, heat of fusion, and heat of vaporization. Know the equations that involve these concepts and be able to use them in calculations. 2. Understand the concepts of energy change and free energy change. Know if a process is spontaneous or not based on the free energy change. 3. Know the definition of pressure, vapor pressure, and atmospheric pressure and be able to convert between pressure units of atm, torr, and psi. 4. List the variables that describe a gas (P,V,n, and T) and be able to write and use the equations for the various gas laws. 5. Explain Dalton's Law of Partial Pressures and define partial pressure. 6. Understand the definitions of density and viscosity. Given the density, and either the mass or volume of a substance, be able to determine the volume or mass (respectively). 7. Know that a liquid in an open container will boil when its vapor pressure is equal to the atmospheric pressure. 8. Describe, compare, and contrast amorphous solids and crystalline solids. 9. Describe the makeup of the four classes of crystalline solids.

Why are some molecular compounds solid while others are gaseous and others are liquid at room temperature?

Competing Powers

? ___________________________forces working to hold particles together as liquids or solids

? _____________________ _______________= Motion = Temperature, work to separate particles

One major factor that is responsible for the varied behavior of solids, liquids, and gases is the nature of the interaction that attracts one particle (atom, ion, or molecule) to another.

What forces hold matter together to make liquids and solids?

The attractive forces that hold molecules together are called intermolecular forces.

3 Types of Intermolecular Forces

? 1) Dipole-Dipole ? 2) Hydrogen Bonding ? 3) London Forces (Induced Dipole Forces)

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Chemistry 108 lecture notes Chapter 5: Solids, Liquids, Gases

Other Noncovalent Interactions Noncovalent interactions are interactions that do not involve the sharing of valence electrons (covalent bonding).

Other noncovalent interactions due to the attraction of permanent charges. ? 1) Salt bridges ? 2) Ion-dipole interactions

? A salt bridge is another name for ionic bond. ? Ion-dipole interactions occur between ions with a full charge and atoms with a

partial charge.

Phase Changes

Energy meets Matter

Adding energy to liquids will overcome the forces holding the molecules together? boiling

Adding energy to solids will overcome the forces holding the molecules together? melting

Calculations Involving Heat Energy

Units of Energy

? One __________________________ is the amount of energy needed to raise the temperature of one gram of water by 1?C

? joule ? 4.184 J = 1 cal

? In nutrition, calories are capitalized ? 1 Cal = 1 kcal

Converting Calories to Joules Example: Convert 60.1 cal to joules

Equivalence statement: 1 cal = 4.184 J

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Chemistry 108 lecture notes Chapter 5: Solids, Liquids, Gases

Calculations Involving Heat Energy

? One of two things will happen if energy is added or removed from matter (assuming no chemical change takes place). ? 1) Change the ______________of the substance ? Example: melt, freeze, vaporize (boil) ? 2) Change the _______________of the substance ? You can only do ______________ of these at a time!!!

1) Phase Change Calculations

Energy calculations for phase changes may be carried out using the tabulated values for: ? ____________ ___ ____________ (symbol = Hfus) for a substance (Table 5.2). ? Energy required to melt one gram of a solid ? Change sign to negative for freezing (liquid to solid) ? ____________ ___ ____________ (symbol Hvap) of a substance ? Energy required to vaporize one gram of a liquid ? Change sign to negative for gas going to liquid

Energy Change = (mass) x (heat of fusion or vaporization) E = (mass) x (Hfus or vap)

Example: Determine the amount of heat needed to melt 155 g of ice at 0?C, we use the heat of fusion of water (79.7 cal/g) as a conversion factor. Note: No Temperature Change! Ice (0oC) Water (0oC)

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Chemistry 108 lecture notes Chapter 5: Solids, Liquids, Gases

Group Work: A patient with a fever is sponged with 50.0 g of 2-propanol. How much heat energy is drawn from the patient when 2-propanol vaporizes? (heat of vaporization for 2-propanol is 159 cal/g)

2) Calculations for Changing the Temperature of Matter

The amount the temperature of an object increases depends on the amount of _________ added (Q).

? If you double the added heat energy the temperature will increase twice as much.

The amount the temperature of an object increases depends on its _______________. ? If you double the mass it will take twice as much heat energy to raise the temperature the same amount.

? Energy calculations may be carried out using the values for the specific heat of a substance.

? Specific heat is the amount of energy required to raise the temperature of one gram of a substance by one Celsius degree.

Substance

Specific Heat (cal/g oC)

Water Ice Steam Ethanol (l) Copper (s) Aluminum (s) Gold (s)

1.000 0.500 0.480 0.586 0.0924 0.0215 0.0310

Energy required = Specific Heat x Mass x Temperature Change

Q = S x m x T

is always: (final) ? (initial) (T) = Tfinal-Tinitial

The table above gives the specific heats of various substances with units of cal/g oC. Specific heats can also be tabulated with units of J/g oC.

? For example, since 1 cal = 4.184 Joules, the specific heat of water is 4.184 J/g oC ? If you use cal/g oC in your calculation, the energy (Q) will be in calories. ? If you use J/g oC in your calculation, the energy (Q) will be in joules.

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Chemistry 108 lecture notes Chapter 5: Solids, Liquids, Gases Example: Calculate the amount of heat energy (in joules) needed to raise the temperature of 7.40 g of water from 29.0?C to 46.0?C

Group Work How much energy needs to be removed from 175 g of water to lower the temperature from 23.0oC to 15.0oC ?

Do this problem, you should get 3.4 x 103 cal for the answer.

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