Solutions, Colloids, and Suspensions are All Mixtures

1
Solutions, Colloids, and Suspensions are All
Mixtures

• Solutions
• Very small particles (lt 1 nm) dissolved in
  solvent (often H2O).
• Clear
• Homogenous (evenly distributed)
• Can not separate by filtration
• NaCl in water, glucose in water

• Colloids
• Larger particles (1 nm- 1 mm) dissolved in
  solvent (often H2O).
• Often cloudy
• Homogenous
• Can separate by filtration
• Milk, shaving cream

• Suspensions
• Larger yet particles (gt 1 mm) suspended in
  solvent (often H2O).
• Visible particles suspended in solvent
• Heterogenous
• Can separate by filtration
• Sand in water, medications that require shaking
  prior to use

2
Diffusion is the Net Movement of Substances From
Areas of Higher Concentration to Areas of Lower
Concentration
3
Semi-Permeable Membranes
Some membranes allow water and small solutes
(dissolved particles) to pass through Cellulose
membrane - used in todays lab Dialysis membrane
- hemodialysis for patients with renal
failure Other membranes allow water but not
other particles - to pass through Red blood
cells
4
Dialysis and Osmosis
Dialysis occurs when water and small particles
in solution can pass through a membrane (but not
colloids) Diffusion of solutes from areas of
higher concentration to lower concentration
occurs Osmosis occurs when water moves
through red blood cell membranes Osmosis is the
net movement of water from areas of lower solute
concentration to areas of higher solute
concentration (In other words, areas of higher
H2O concentration to areas of lower H2O
concentration)
5
Osmosis is the Net Movement of Water Across a
Semi-Permeable Membrane From a Solution of Lower
Concentration Solute to a Solution of Higher
Concentration Solute
This selectively permeable membrane is only
permeable to water - sugar can not cross it.
Thus, water will diffuse across the membrane to
approach closer to equal concentration on both
sides. This creates a pressure difference -
osmotic pressure.
6
Hypotonic, Isotonic, and Hypertonic Solutions
Hypertonic Higher solute concentration than
inside cell Water moves out of cell
Hypotonic Lower solute concentration than inside
cell Water moves into cell
Isotonic Same solute concentration as inside
cell No net movement of water 0.9 NaCl
(saline) 5 glucose (dextrose)
7
Effect of Isotonic, Hypertonic and Hypotonic
Solutions on Red Blood Cells (RBCs)
RBC in isotonic solution Same solute
concentration as inside cell No net movement of
water
RBC in hypertonic solution Higher solute
concentration than inside cell Water moves out
of cell
RBC in hypotonic solution Lower solute
concentration than inside cell Water moves into
cell
8
Notes on This Experiment

• Start with Part B. Set up dialysis bag and allow
  to soak for 40 minutes.
• Skip 20 minute measurement.
• 2) While waiting, work on Part A and the
  problems on page 71.
• Also start filtration in Part C (filtration is
  slow)
• Continue with Part B while filtration is in
  progress.

Place silver (Ag) waste in Waste Container
3. Place iodine and Benedicts reagent solutions
in Waste Container 1. Glucose, NaCl, and starch
solutions can go down sink.