Chapter 24 - Molecular Mixing

Key Terms:

Objectives of chapter:

• distinguish between molecular attractions and chemical bonds
• compare and contrast the different types of molecular attractions
• understand the concept of solubility
• articulate how soaps and detergents work

Outline:

24.1 submicroscopic particles electrically attract one another

24.2 polar molecules can induce dipoles in non-polar molecules

24.3 Solubility is a measure of how well a solute dissolves

24.4 Solubility changes with temperature and pressure

Solutions:

• Solutions - a mixture that is homogenous in which the particles are evenly spread out,
  so evenly that it doesn't even exhibit the tyndall effect.
• Solvent:- doing the dissolving, usually the larger quality.
• Solute- Being dissolved usually the smaller quantity.

examples of solutions

Solute	Solvent	Example	states being combined
Salt	water	salt water	S:L
Fruit Juice	Corn Syrup	Cheap Juice	L:L
Carbon Dioxide CO2	Coke syrup	Coke	G:L
O3	Air at atmosphere	air pollution	G:G
Copper	Zinc	Brass Alloy	S:S

The dissolving process :

• To speed up rate of dissolving:
  • Increase the energy. This turns up the heat, causing molecules to separate, it "excites" the molecules.
  • Or you can decrease the molecule size and increase surface area.
  • heat
  • physical stirring
  • pressure
• Solvents and solutes must be of the same type in order to dissolve - ie polar vs non polar

Solubility and concentration:

• there is a maximum amount that can be dissolved in a given solution - solubility
• as concentration increases the solubility decreases making it harder to dissolve something.
• concentration is the ratio of solute and solvent, if you change one or the other's quantity you change the concentration
• supersaturated solutions exceed the normal solubility - usually as a result of heat and pressure.

Conductivity and Boiling point as related to concentration.

• as concentration increases boiling point and conductivity increase

24.5 Soap works by being both polar and non polar

Chapter links

class text - conceptual physical science

PCDS useful links - sorted by topic

 

Related labs, activities and videos

crime lab - using chromatography to separate a mixture by polarity

pure sweetness - purification of crystals

Practice Book Exercises

solutions - page 95

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