1. Mixtures & Solubility – Part I

2. Mixtures are a physical blend of at least two substances; have variable composition. They can be either:
Heterogeneous – the mixture is not uniform in composition
Chocolate chip cookie, gravel, soil.
Homogeneous - same composition throughout; called “solutions”
Kool-aid, air, salt water
Every part keeps it’s own properties.

3. Phase?
The term “phase” is used to describe any part of a sample with uniform composition of properties.
A homogeneous mixture consists of a single phase
A heterogeneous mixture consists of two or more phases.

4. Separating Mixtures
Some can be separated easily by physical means: rocks and marbles, iron filings and sulfur (use magnet)
Differences in physical properties can be used to separate mixtures.
Filtration - separates a solid from the liquid in a heterogeneous mixture (by size)

5. Separation of a Mixture
Components of dyes such as ink may be separated by paper chromatography.

6. Separation of a Mixture
Distillation: takes advantage of different boiling points.
NaCl boils at 1415 oC

7. Remember… all substances are either:
a) elements, or
b) compounds

8. Substances: element or compound
Elements- simplest kind of matter
cannot be broken down any simpler and still have properties of that element!
all one kind of atom.
Compounds are substances that can be broken down only by chemical methods
when broken down, the pieces have completely different properties than the original compound.
made of two or more atoms, chemically combined (not just a physical blend!)

9. Compound vs. Mixture Compound Mixture Made of one kind of material
Made of more than
one kind of material
Made by a
chemical change
physical change
Definite
composition
Variable

10. Understanding Solutions
Solution - homogeneous mixture
Solute - substance being dissolved
Solvent - present in greater amount

11. Mixtures & Solubility – Part II

12. Solvation
Solvation – the process of dissolving
solute particles are surrounded by solvent particles
First...
solute particles are separated and pulled into solution
Then...

13. Recall the states of matter symbols…
(s) = solid
(l) = liquid
(aq) = aqueous (made with water)
(g) = gas

14. Solvation
“Like Dissolves Like”
NONPOLAR
POLAR

15. Solvation Soap/Detergent polar “head” with long nonpolar “tail”
dissolves nonpolar grease in polar water

16. Solubility UNSATURATED SOLUTION more solute dissolves
no more solute dissolves
SUPERSATURATED SOLUTION
becomes unstable, crystals form
concentration

17. Solubility Solubility
maximum grams of solute that will dissolve in 100 g of solvent at a given temperature
varies with temp
based on a saturated soln

18. Solubility Solubility Curve
shows the dependence of solubility on temperature

19. Solubility Rules 1. Higher temp. usually increases solubility
2. Higher pressure increases solubility of a gas
3. Polar solutes will dissolve in like polar solvents; nonpolar solutes will dissolve in nonpolar solvents