Define a Solution Summary Activity Read pp. 266 – 268 Define the following terms: solution, homogeneous mixtures, solute, solvent, alloy, and aqueous

Define a Solution Summary Activity• Read pp. 266 – 268

• Define the following terms: solution, homogeneous mixtures, solute, solvent, alloy, and aqueous solutions

• How are solutions classified? Utilize p. 266 Table 1 for examples

• What are some properties of aqueous solutions? Provide key terms, definitions and examples of each.

• Assigned Questions:

• p. 269 Practice UC #1, 2, 3, 4, 5, 6, 71






• p. 269 Practice UC #1, 2, 3, 4, 5, 6, 72






• p. 269 Practice UC #1, 2, 3, 4, 5, 6, 73






• p. 269 Practice UC #1, 2, 3, 4, 5, 6, 74

Explaining Solutions

Explaining Solutions 6

Bonding ForcesIntramolecular Forces• “intra” means within• forces that bond atoms and ions within a

compoundIntermolecular Forces• “inter” means between• responsible for how molecules arrange

themselves in an orderly fashion (i.e. lattice structure)

• relatively weak compared to intramolecular (e.g. covalent bonds)


Polar Covalent Bonds

• when atoms are identical (e.g. Cl2) the electrons are share equally

• however, when two different elements form bond the electron sharing is unequal, bonding electrons spend more time near one atom than the other

• Ex. H-Cl (because Cl is more electronegative than H, it has a greater ability to attract electrons when bonded and as a result Cl is slightly negative and H is slightly positive)


• “slightly” is represented by the Greek letter delta () which represents small difference

Example: + H – Cl -

• In general, if the absolute value of the difference in electronegativities is 1.7 or less the bond tends to be polar covalent (Review p. 83 Table 1 and p. 84 Figure 3)




Polar Molecules

• if a molecule contains polar covalent bonds, the entire molecule may have a positive end and a negative end. Therefore, called a polar molecule

• however, not all molecules with polar covalent bonds are polar molecules (e.g. HCl and CCl4)

• Review Guidelines for Predicting Polar and Nonpolar Molecules p. 85 Table 3




Intermolecular Forces

van der Waals forces (2 types)

• London dispersion forces– exist between ALL molecules, polar or

nonpolar– result of temporary shift of electron “cloud”

around atoms in molecule, they are short-lived dipoles (lasts tiny fractions of seconds)



• Dipole-dipole forces

– forces of attraction between oppositely charged ends of polar molecules

– positive end of each molecule attracts negative end of neighbouring molecules (kinda, like a weak version of ionic bond)



Hydrogen Bonds

• occur among highly polar molecules containing F – H, O – H, and N –H bonds

• hydrogen bonds are much stronger than van der Waals

• water tends to “stick together” because of these bonds



Intermolecular Forces


http://www.youtube.com/watch?v=S8QsLUO_tgQ

SEATWORK

Read and Summarize pp. 273 – 275

- Explaining molecular substances in water

- The effects of polarity and hydrogen bonds

Read Lab Exercise

Predicting High and Low Solubilities

(pp. 275-277)

- Within a small group answer the Prediction (a)


23

Predicting High and Low Solubilities (pp. 275-277)

Highest Solubility - Acetic Acid and Methanol• Molecules are polar• Formation of hydrogen bonds with water molecules

High Solubility - Dimethyl ether• Molecule is polar• Presence of oxygen atom means some hydrogen bonding with O-

H ends of water molecules

Slightly Soluble - Carbon dioxide and Oxygen• Should be non-polar, but oxygen presence means that there is a

possibility of some hydrogen bonding with water molecules.

Insoluble - Propane and Tetrachloromethane• Nonpolar molecules• Little or no solubility in water, cannot participate in dipole-dipole

forces and hydrogen bonding


SEATWORK

Assigned Questions

p. 277 # 3, 4, 5

Read and Summarize pp. 277 - 279

- Ionic compounds in water

- Explaining non-aqueous mixtures

- Water – “The Universal Solvent”

Documents

Define a Solution Summary Activity Read pp. 266 – 268 Define the following terms: solution, homogeneous mixtures, solute, solvent, alloy, and aqueous