Polarity and Hydrophobic & Hydrophilic Molecules Learning Goal: I will be able to describe the properties of water that make it a good solvent for polar compounds I will explain the process of how soap works by using the terms hydrophobic and hydrophilic I will be able to describe what acids and bases are and how they compare to water

What are we talking about?

RECAP: Draw the shape of a water molecule, and show the polar ends. Due to differences in electronegativities, water is slightly charged at its poles Oxygen takes on a slight – charge Hydrogens take on a slight + charge Why are ionic compounds electrolytes? Think/Pair/Share: How might 2 or more water molecules interact with each other?

Solubility: How easily a substance dissolves The general rule is "like dissolves like" Polar substances dissolve polar substances Non-polar substances dissolve non-polar substances HYDROPHOBIC: HYDROPHILIC: Often, the subscript “(aq)” is visible. This subscript means that aqueous substances are soluble in water. A polar molecule that can bond with water is called a hydrophilic molecule. A nonpolar molecule that cannot bond with water is called a hydrophobic molecule.

H-Bonding Is Responsible for Density of Ice Being Less than Water H-bonds lock into lattice structure in the solid state

Ice Solid water is less dense than liquid water, allowing it to float

Fun Water Facts About how much of our body is made up of water? How long can we go without water? True or False: Good hydration can prevent arthritis. 70% 1 week

Water is the universal solvent Water can dissolve many hydrophilic (water loving) substances Ionic compounds Other polar compounds Any substance that dissolves in water is called a solute. Water, then, is a solvent. Hydration is the process of water molecules surrounding ions to make “spheres of hydration” Video: https://www.youtube.com/watch?v=DAilC0sjvy0

Think/Pair/Share: Can water dissolve non-polar oil? Why or why not? Can water pass freely through the cell membrane?

Some substances do not dissolve readily in water because they are non-polar solutes Oil (fats or lipids) is an example of a hydrophobic – “water-fearing” - substance Application: How does soap work to clean grease/oil from our dishes?

How soap works: micelles Soap can suspend oil/dirt in such a way that it can be removed

Soap is an excellent cleanser non-polar CH2 units; ionic/polar COO-Na+ group

Grease and oil are non-polar and insoluble in HOH. When soap is added to oil-containing solution, the non-polar hydrocarbon portion of the soap attaches to the non-polar oil molecules.

A micelle then forms—with nonpolar solutes (grease/oil) in the centre. The outside of the micelle is polar (water soluble) and now the grease and oil can be washed away.

3-D diagram of a micelle . . . Hydrophillic (water loving) head Hydrophobic (water fearing) head

Isn’t our cell membrane made of fat? What happens when soap comes in contact with our cell membrane?

Acids & Bases: When 2 water molecules interact, one molecule gains a hydrogen (to become H3O+, hydronium ion) while the other loses a hydrogen (and becomes OH-, hydroxide ion). This process is called the autoionization of water.

Acids are defined as substances that increase the concentration of H+ (or H3O+) ions in solution. Bases are defined as substances that increase the concentration of OH- ions in solution.

When an acid is mixed with a base, the result is a neutralization reaction. Neutralization reactions produce water and a salt.

A solution with a pH of 7 is considered neutral (equal amounts of H3O+ and OH-). Solutions whose pH is less than 7 are acidic (more H3O+). Solutions whose pH is greater than 7 are basic (more OH-).

How Did We Do? Learning Goal: I will be able to describe the properties of water that make it a good solvent for polar compounds I will explain the process of how soap works by using the terms hydrophobic and hydrophilic I will be able to describe what acids and bases are and how they compare to water