Crystal Honeycomb Structure of Ice

What happens when solute is added?

Osmotic Pressure• A colligative property observed when solutions of higher and

lower solute concentration are separated by a semipermeable membrane like dialysis tubing or cell wall. – Solvent molecules travel through the semipermeable

membrane by a process called osmosis. – The net flow of solvent molecules in one direction causes a

pressure difference known as osmotic pressure.– In theory the net flow of solvent molecules = zero

when ?????• Osmotic pressure is the pressure that must be applied to a

system to prevent the net flow of solvent molecules through a semipermeable membrane.

• As number of solvent molecules increases, osmotic pressure ???

Osmotic Pressure and Cell Shape

Tonicity and Cell Shape. Tonicity refers to the tone or firmness of a cell. Isotonic Solution:

[Solute] in the solution = [Solute] in the cellRate of water into = Rate of water out of cell

Hypotonic Solution: [Solute] in the solution < [Solute] in the cellRate of water into cell > Rate of water out of cell

Hypertonic Solution: [Solute] in the solution > [Solute] in the cellRate of water into cell < Rate of water out of cell

Isotonic Solution Hypotonic Solution Hypertonic Solution

Fun Facts• Absorption of water by trees:

tree sap is a more concentrated solution than ground water. The difference in concentration causes water to travel through tree roots via osmosis. Osmotic pressure can exceed 20 atm.

• Food preservation: Packed onto food, salt causes microbes on the surface to shrivel as they lose water. The word salary comes from salt.

Petroleum Refining

• In petroleum refining, the refining process does not separate each compound contained in crude oil. It produces several distinctive mixtures called fractions. The process is known as fractional distillation. Compounds in each fraction have a particular range of boiling points and specific uses.

• The crude oil is heated to about 400˚C in a tower that is 30 meters (100 feet) tall. The temperature is higher at the bottom of the column and decreases toward the top. Trays are arranged at appropriate heights inside the column to collect the various fractions.

• The vaporized molecules move upward in the column. The lighter, smaller molecules having the lower boiling points and are drawn off at the top of the column. The heaviest fractions with the highest boiling points are drawn off at the bottom of the column.