1. Solutions, Acids, and Bases
Chapter 8
Solutions, Acids, and Bases

2. 8.1 Formation of Solutions

3. Dissolving
Recall that a solution is a homogeneous mixture of two or more substances
Every solution has two components:
Solute
Substance whose particles are dissolved in a solution
Solvent
Substance in which the solute dissolves
Ex. Seawater – water is solvent, salt is solute

4. Dissolving
Solutes and solvents can take the form of solid, liquid, or gas
Solution takes state of solvent
Substances can dissolve in water in three ways
Dissociation
Dispersion
Ionization

5. Dissociation of Ionic Compounds
For a solute to dissolve in water
The solute and solvent particles must attract to one another
The solute particles are attracted and the solvent particles are attracted to one another
So, before a solution can form, those attractions must be overcome
Process in which an ionic compound seperates into ions as it dissolves is called dissociation

6. Dispersion of Molecular Compounds
The water in your saliva dissolves the sugar and flavoring in candy throughout your mouth
Sugar dissolves in water by dispersion, or breaking into small pieces that spread throughout the water
Both sugar and water are polar, therefore attract
When enough water molcules have surrounded the sugar molecule, sugar molecule breaks free and is pulled into solution

7. Ionization of Molecular Compounds
HCl – molecular compound where hydrogen and chloride share an electron
When HCl gas dissolves in water, the H molecule is transferred to water
H30+ and Cl- are produced
When a neutral molecule gain or lose electrons it is known as ionization
This is a chemical change
Unlike dispersion and dissociation

8. Properties of Liquid Solutions
Three physical properties of a solution that can differ from those of its solute and solvent are:
Conductivity
Freezing point
Boiling point

9. Conductivity Solid sodium chloride is a poor conductor
When it dissociates in water, the sodium and chloride ions are able to move freely
They will then conduct electricity

10. Freezing Point and Boiling Point
MgCl2 is what is sometimes spread on icy roads
When it dissolves in melting ice, it dissociates into Mg2+ and Cl-
These ions are able to interfer with freezing process
Salted roads have a freezing point of -15°C

11. Freezing Point and Boiling Point
Solute can also raise boiling point
ex. Coolant used in most car radiators
Adding ethylene glycol to water raises the boiling point
Solution helps prevent the engine from overheating
Also prevents the the liquid from freezing in the winter

12. Heat of Solution
During the formation of a solution, energy is either released or absorbed
Can be described as either exothermic or endothermic
Dissolving sodium hydroxide in water is exothermic, releases heat
How it Works box explains how cold packs are used

13. Heat of Solution
In order for a solution to form, all attractions must be broken
That requires energy
Formation of solutions, releases energy
The difference between these energies is called the heat of solution

14. Factors Affecting Rates of Dissolving
Reates of dissolving depend on the frequency and energy of collisions
Formation of solutions, collisions occur between solute and solvent particles
Factors that affect the rate of dissolving include:
Surface area
Stirring
temperature

15. Factors Affecting Rates of Dissolving
The greater the surface area of a solid solute, the more requent the collision are between the solute and the solvent particles
Increase surface area by breaking into smaller pieces
Stirring
Moves dissolved particles away from surface
Allows more collisions between solute and solvent

16. Factors Affecting Rates of Dissolving
Increasing temperature is another way to speed up dissolving
Increase in temperature causes the particles to move faster
Both the number of collisions and the energy of these collisions increases
Goes into solution more quickly

17. Review Quiz
1. What do we call the substance whose particles are dissolved in a solution?
2. What do we can the substance the dissolves the particles in a solution?
3. When a neutral molecule gains or loses electrons, it is called ________?
4. List two of the three factors that affect the rate of dissolving?

18. 8.2 Solubility and Concentration

19. Solubility Solubility Solutions are described as:
The max amount of a solute that dissolves in a given amount of solvent at a constant temperature
Usually expressed in grams of solute in 100g of solvent
Solutions are described as:
Saturated
Unsaturated
Supersaturated

20. Solubility Saturated Sugar is very soluble in water
At 20 degrees C you can dissolve grams of sugar in 100g of water
What will happen if you try to dissolve more than that?
The extra sugar will not go into solution
The solution is already saturated
One that contains as much solute as the solvent can hold at a given temperature

21. Solubility Unsaturated
A solution that has less than the max amount of solute that can be dissolved
many beverages are unsaturated

22. Solubility Supersaturated
If you heat a solvent above the average temperature it can dissolve more solute
If you then carefully cool the solvent back to the average without jarring it, you may be able to keep the extra solute in the solution
Supersaturated solution
One that contains more solute than it can normally hold at a given temperature
Very unstable
If a tiny particle falls into a supersaturated solution, the extra solute may rapidly fall out

23. Factors Affecting Solubility
Have you ever tried to wash oil or grease off your hands?
Will not come off in just water, but in soapy water it will wash off
Not soluble in water, but in soapy water it is
Three factors that affect solubility:
Polarity of the solvent
Temperature
pressure

24. Factors Affecting Solubility
Polar and Nonpolar Solvents
Oil molecules are nonpolar, water is polar
Common guideline for predicting solubility is ‘like dissolves like’
More likely to dissolve if solute and solvent are both polar or both nonpolar
Soap molecules have a polar and non polar end
Makes it easy to dissolve oil

25. Factors Affecting Solubility
Temperature
In general the solubility of a solute increases when you increase the temperature of the solvent
When water temp increases, bubbles start to come out of the water
These are gas bubbles that are dissolved in water
Unlike most solids, gases usually become less soluble as the temperature of solvent increases

26. Factors Affecting Solubility
Pressure
Incresing the pressure on a gas increases its solubility in a liquid
Pressure of carbon dioxide in a 12 oz can of soda at room temp can by two to three times atmospheric pressure

27. Concentration of Solutions
The amount of solute dissolved ina specified amount of solution
Can be expressed as:
percent by volume
percent by mass
molarity

28. Percent by Volume
Often times on fruit juice bottles have a percentage of real fruit juice in it.
Ex. 27% real fruit juice
To calculate the concentration as a percent by volume:
Page 238

29. Percent by Mass

30. 8.3 Properties of Acids and Bases

31. Identifying Acids Acid
Compound that produces hydronium ions (H3O+) when dissolved in water.
Acids have certain chemical and physical properties that are similar
Sour taste
Reactivity with metals
Ability to produce color changes in indicators

32. Sour Taste Foods that taste sour often contain acids
Lemons, grapefruits, limes, and oranges all contain citric acid
Dairy products that have spoiled contain butyric acid
NEVER TEST AN ACID BY TASTING IT!

33. Reactivity with Metals
Sometimes when you cover food with aluminum foil, it gets small holes in it, or the food starts to taste metallic
Foods with tomatoes contain citric acid which will react with aluminum (metal)
Single replacement reaction

34. Color Changes in Indicators
Any substance that changes color in the presence of an acid or base
Common idicator is litmus
Dye derived from plants called lichens
Blue litmus paper turns red in the presence of acid

35. Identifying Bases Base
A compound that produces hydroxide ions when dissolved in water
Have certain physical and chemical properties in common
Bitter taste
Slippery feel
Ability to produce color changes in indicators
Do not react with metals (usually)
Zinc and aluminum react vigorously with sodium hydroxide

36. Bitter Taste Have you ever tasted unsweetened chocolate?
Sometimes called baking chocolate…
Coco beans contain a base called theobromine that gives unsweetened chocolate its bitter taste
Cough syrups and other liquid medicines contain similar bases
Fruit flavorings are added to mask the bitter taste

37. Slippery Feel
Wet soap and many cleaning supplies are slippery because they contain bases
When wet, some rocks feel slippery
Water dissolves compounds trapped in the rocks, producing basic solution

38. Color Changes in Indicators
Bases turn red litmus paper blue.
Will change back to red if you put acid on the paper
Phenolphthalein is another example of an acid-base indicator
In solution containing base, solution is red
In solution containing an acid, colorless
Hydrangeas contain natural indicators
Color depends on acid/base soil
Acid soil – bluish-purple
Basic soil - pink

39. Neutralization and Salts
Sometimes people squeeze lemon juice over fish
Fish is basic and can sometimes taste bitter
Lemon juice contains acids, makes it taste less bitter
Reaction between acid and base is called neutralization
Negative ions in acid combine with positive ions in base to form a salt
Hydronium ions combine with hydroxide ions to form water

40. Proton Donors and Acceptors
Acids lose, or ‘donate’ protons
Bases accept, forming water, a neutral molecule
Water can act as either an acid or a base depending on what it is reacting with