1. Unit 8 Part I Types of Mixtures

3. Mixtures are either homogeneous or heterogeneous
A heterogeneous mixture is made of different substances that remain physically separate and can be distinguished from each other.
Heterogeneous mixtures often have more than one phase and can have regions with uniform composition and properties.
Heterogeneous mixtures can be separated by a physical change.
A homogeneous mixture has the same uniform appearance and composition throughout.
Many homogeneous mixtures are commonly referred to as solutions.

4. Types of Heterogeneous Mixtures
Suspension: A mixture in which particles of a material are less evenly dispersed through a liquid or gas. E.g. mud, freshly squeezed orange juice.
A suspension separates into different layers when you stop stirring it is

5. Types of Heterogeneous Mixtures
Colloid – A mixture consisting of tiny particles that are intermediate in size between those in solution and those in suspensions and that are suspended in a solid, liquid or gas. E.g. Fog, smoke, whipped cream, mayonnaise, etc.
Stable colloid particles are too small to be filtered out and do not settle.

6. Colloids in Biological Systems
Water can interact with other polar molecules, but cannot interact with nonpolar molecules (like oils and fats)
In order for water to be able to interact with nonpolar molecule, a molecule called as an emulsifier has to act as a bridge between the nonpolar molecule and water.
Emulsifiers have a polar, hydrophilic (water-loving) end and a nonpolar, hydrophobic (water-hating) end.
Sodium stearate is one example of such a molecule.
Sodium stearate can help water form a colloid with nonpolar oils and fats so they can be removed using water.

7. Emulsifiers allow nonpolar molecules to mix with water
Emulsification - To make a suspension of tiny droplets of one liquid in a second liquid. By making an emulsion, one can mix two liquids that ordinarily do not mix well, such as oil and water.

8. Soap is also an emulsifier
When grease or oil (non-polar hydrocarbons) are mixed with a soap- water solution, the soap molecules work as a bridge between polar water molecules and non-polar oil molecules.
Since soap molecules have both properties of non-polar and polar molecules the soap can act as an emulsifier.
This means that soap can suspend oil/dirt in such a way that it can be removed.
The soap will form tiny clusters called micelles.
The water-loving (hydrophilic) part of the soap molecules points outwards, forming the outer surface of the micelle.
The oil-loving (hydrophobic) parts group together on the inside, where they don't come into contact with the water at all.
Micelles can trap fats in the center.
Since the micelle is soluble in water, it can easily be washed away.

10. Objectives:
Students will be able to cite evidence used to formulate methods to increase the solubility of a solute.
Students will be able to compare solutions based on their concentration.
Students will be able to differentiate between unsaturated, saturated and supersaturated solutions based on their defining characteristics
Assignment: None
Focus:
Soap can remove grease and oil from your skin because it acts as
a. an emulsifier to surround the oil. c. a solvent to dissolve the dirt.
b. an acid to neutralize the dirt. d. a salt to make water harder.

11. Solutions are Homogeneous Mixtures
Solution – homogeneous mixture of two or more substances of ions or molecules. E.g. NaCl (aq)
Solutions will not separate under normal circumstances.
Solvent = A substance capable of dissolving another substance. The component of a solution that does not change its state in forming the solution or the component which is present in greater amount.
Solute = The substance that is dissolved in another substance. The component of a solution that changes its state in forming the solution or the component which is present in the smaller amount.
Gaseous Solutions = gases are completely miscible in each other.
Liquid Solutions = gas, liquid or solid solute dissolved in liquid solution.Liquids that mix to form a single layer are said to be miscible.
Solid = mixture of two solids that are miscible in each other to form a single phase.

12. How do solvents dissolve solute?
The intermolecular forces between solute and solvent particles must be strong enough to compete with those between solute particles and those between solvent particles.

13. Water dissolving Salt

14. How Does a Solution Form?
As a solution forms, the solvent pulls solute particles apart and surrounds, or solvates, them.

15. Factors Affecting Solubility
Chemists use the axiom “like dissolves like”:
Polar substances tend to dissolve in polar solvents.
Nonpolar substances tend to dissolve in nonpolar solvents.
The more similar the intermolecular attractions, the more likely one substance is to be soluble in another.
Example:Glucose (which has hydrogen bonding) is very soluble in water, while cyclohexane (which does not have hydrogen bonding) is not.

17. Solution Concentration
An aqueous solution consists of at least two components, the solvent (water) and the solute (the stuff dissolved in the water).
Usually one wants to keep track of the amount of the solute dissolved in the solution.
We call this the solution concentration.
To keep things simple we will think of concentration as the ratio of solute to solvent.
The more solute particles there are per amount of solvent, the more concentrated the solution is.

18. Solutions and their concentrations
Unsaturated
Less than the maximum amount of solute for that temperature is dissolved in the solvent.
Therefore, it can dissolve more solute at the current conditions.

19. Solutions and their concentrations
Saturated
Solvent holds as much solute as is possible at that temperature.

20. Solutions and their concentrations
Supersaturated
Solvent holds more solute than is normally possible at that temperature.
These solutions are unstable.
The solute will precipitate out of the solution as it cools down.
Crystallization can usually be stimulated by adding a “seed crystal” or scratching the side of the flask.

21. Objectives:
Students will be able to connect the biological process of osmosis to a difference in the concentration of a solution on opposite sides of a semipermeable membrane.
Students will be able to explain how hypertonic, hypotonic and isotonic solutions affect cells
Assignment: None.
Focus:
Water can dissolve charged particles because
a. it is an ionic compound. c. it is solid at a temperature of 0°C.
b. its atoms have partial charges. d. its molecular weight is extremely low.

22. Osmosis occurs because of difference in solution concentration
Osmosis – Facilitated diffusion of water.
Facilitated diffusion – Substances move from high to low concentration, but cannot pass directly through a membrane, instead passing through protein channels.
Some substances form semi permeable membranes, allowing some smaller particles to pass through, but blocking other larger particles.
In biological systems, most semi permeable membranes allow water to pass through, but solutes are not free to do so.

23. Osmosis occurs because of difference in solution concentration
In osmosis, there is net movement of solvent (water) from the area of higher solvent concentration (lower solute concentration) to the area of lower solvent concentration (higher solute concentration).
Concentrated Solution
Dilute Solution
Solute concentration
Higher Concentration
Lower Concentration
Solvent concentration (Water)
Water moves
Moves into the solution
Moves out of the solution

24. Osmosis in Blood Cells
If the solute concentration outside the cell is greater than that inside the cell, the solution is hypertonic.
Water will flow out of the cell, and crenation results.
Crenation - A cell shrinks by osmosis because water leaves cell.

25. Osmosis in Blood Cells
If the solute concentration outside the cell is less than that inside the cell, the solution is hypotonic.
Water will flow into the cell, and hemolysis results.
Hemolysis - The breakdown or destruction of red blood cells so that the contained hemoglobin is freed into the surrounding medium.

26. Osmosis in Blood Cells
An isotonic solution refers to two solutions having the same concentration and therefore the same osmotic pressure across a semipermeable membrane.
This state allows for the free movement of water across the membrane without changing the concentration of solutes on either side