1. Solutions, Acids and Bases
Chapter 8

2. Formation of Solutions
For a solution to form, one substance must dissolve in another.
Even though we usually think of a solid dissolving in a liquid, any state of matter can become part of a solution.
Scuba divers breathe with the aide of compressed air(78% nitrogen). As a diver descends (the deeper the diver goes), the greater is the pressure of the air in the diver’s lungs and the more nitrogen dissolves in the blood and tissues of the body. If divers surface too quickly, the nitrogen that has dissolved in the blood and tissues can bubble out of the solution and become trapped in joints causing great pain (“the bends”).

3. A Quick review of Solutions
A solution is a homogeneous mixture of two or more substances.
Every solution has two types of components: a solute (salt) and a solvent(water).
For a solute to dissolve in water, the solute and solvent particles must attract one another.
Solutes and solvents can be solids, liquids or gases.

4. Dissolving
Substances can dissolve in water three ways:
Dissociation of Ionic Compounds: sodium chloride crystal and water
Dispersion of Molecular Compounds: hard candy and saliva
Ionization of Molecular Compounds: HCl and water
The process in which neutral molecules
gain or lose electrons is known as ionization.

5. Properties of Liquid Solutions
Three physical properties of a solution that can differ from those of its solute and solvent are as follows:
Conductivity
Sodium chloride dissociates in water
Hydrogen chloride ionizes in water
Freezing point
Magnesium chloride dissociates and interferes with the freezing process changing it from 0ºC to as low as -15ºC
Boiling point
Ethylene glycol and water (coolant in most car radiators) raises the boiling point of water from 100ºC to prevent overheating

6. Heat of Solution
During the formation of a solution, energy is either released or absorbed.
Sodium hydroxide dissolves in water and becomes warmer (exothermic: releasing energy to the surroundings)
Ammonium nitrate , used in cold packs, dissolves in water and becomes colder (endothermic: absorbing energy from the surroundings)
In order for a solution to form, both the attractions among solute particles and the attractions among solvent particles must be broken. Breaking of attractions requires energy.
As the solute dissolves, new attractions form and the formation of attractions releases energy. The is the difference between these energies.
heat of solution

7. Factors Affecting Rates of Dissolving
Factors that affect the rate of dissolving include surface area, stirring and temperature.
The more frequent the collisions between the solute and solvent, the faster rate of dissolving.

8. Solubility and Concentration
Lemonade, Iced tea, and hot tea can all “hold” different concentrations of sugar.
They each have different factors for solubility of sugar.

9. Solubility
The maximum amount of a solute that dissolves in a given amount of solvent at a constant temperature is called solubility.
Grams of solute per 100 grams of solvent at a specified temperature
Knowing the solubility of a substance can help you classify solutions based on how much solute they contain.
Solutions are described as saturated(solvent filled with solute), unsaturated(solvent does not fill the solute) or supersaturated(more solute than the solution can hold), depending on the amount of solute in solution at a given temperature.

10. Factors Affecting Solubility
Three factors affect the solubility of a solute.
Polar and Nonpolar Solvents – oil is soluble in soapy water
-“like dissolves like”
Temperature – generally, solubility increases as the temperature increases (iced tea versus hot tea with sugar)
Pressure – 12-ounce can of soda/carbonation (CO2) dissolved in a liquid

11. Concentration of Solutions
Concentration can be expressed as percent in three ways.
Percent by Volume
Percent by Mass
Molarity

12. Properties of Acids and Bases
Sodium hydroxide (a base) is added to a mixture of animal/vegetable fats and boiled until the sodium hydroxide reacts with the fats producing glycerol and soap. After glycerol is separated from the soap, the soap is purified and other chemicals are mixed in for color and scent.

13. Identifying Acids
An acid is a compound that produces hydronium ions when dissolved in water.
Some general properties of acids include sour taste, reactivity with metals, and ability to produce color changes in indicators.
Sour Taste: lemons, grapefruits, limes, and oranges (citric acid)
vinegar (acetic acid)
Reactivity With Metals: aluminum foil over spaghetti sauce (citric acid) – a single replacement reaction
Color Changes in Indicators: litmus paper (a common indicator) turns red in the presence of an acid

14. Identifying Bases
A base is a compound that produces hydroxide ions when dissolved in water.
Some general properties of bases include bitter taste, slippery feel, and ability to produce color changes in indicators.
Bitter Taste: unsweetened chocolate, many cough syrups
Slippery Feel: wet soap, some wet rocks
Color Changes in Indicators: bases turn litmus paper blue

15. Other indicators Phenolphthalein: In a basic solution, is red
In an acidic solution, is colorless
Natural indicators: flowers, like hydrangeas
In basic soil, flowers are pink
In acidic soil, flowers are blue

16. Neutralization and Salts
The reaction between an acid and a base is called neutralization.
FISH – BASE LEMON – ACID
REACTION MAKES FISH TASTE LESS BITTER
This reaction is called neutralization.
The neutralization reaction between an acid and a base produces a salt and water.

17. Strength of Acids and Bases
Certain compounds of chlorine are dissolved in swimming pool water to prevent the growth of bacteria.
The concentration of hydronium ions in solutions must be carefully controlled.
Determining the concentration of hydronium or hydroxide ions is one way to determine the acidity or basicity of a solution.

18. The PH Scale
Chemists use a number scale from 0 to 14 to describe the concentration of hydronium ions in a solution.
The PH of a solution is a measure of its hydronium ion concentration.
7 is neutral
Acids have a pH less than 7
Bases have a pH greater than 7
The lower the pH value, the greater the H3O+ ion concentration in solution is. The higher the pH value, the lower the H3O+.

19. Strong Acids and Bases To review…
Some reactions go to completion while other reach equilibrium
When certain acids and bases dissolve in water, the formation of ions from the solute almost goes to completion. These acids and bases are classified as strong.
Strong Acids
When strong acid dissolve in water, they ionize almost completely.
Examples: sulfuric acid and nitric acid
Strong Bases
Strong bases dissociate almost completely in water.
Examples: calcium hydroxide and potassium hydroxide

20. Weak Acids and Bases
Weak acids and bases ionize or dissociate only slightly in water.
Weak Acids
Citric acid in orange juice, acetic acid in vinegar
Equilibrium favors the reactants over the products so few ions form in solution
Have a higher pH
Weak Bases
Toothpaste and shampoo contain weak bases
Ammonia (colorless gas with distinctive smell)
Buffers
A solution that is resistant to large change in pH
Prepared by mixing a weak acid and its salt or a weak bases and its salt
pH is relatively constant

21. Electrolytes
Sports drinks taste salty because they contain salts of elements; they help restore the balance of ions in your body.
Electrolytes ionize or dissociate into ions when they dissolve in water and results in a solution that can conduct an electric current.
Strong acids and bases are strong electrolytes because they dissociate or ionize almost completely in water.
Batteries and fuel cells also produce electricity and contain electrolytes.

22. River of Life
Class Participation Opportunity: Write a research paper that includes the following concepts: 1. compounds in blood 2. blood flow through the body 3. maintaining blood’s pH 4. scientists who have contributed to our understanding of blood Your paper should include information found on pages It should also contain information from two other sources.

23. Formal Lab Report: Your Way
Possible investigative questions: Determining Solubility 1. How can you determine the solubility of a substance in water? Comparing Solubilities and Rates of Dissolving 2. How does surface area affect the rate of dissolving and solubility? 3. How does temperature affect the rate of dissolving and solubility? Testing Antacids 4. Which antacid neutralizes stomach acid with the smallest number of drops? Comparing Antacids 5. Which brand of antacid neutralizes the most acid per dose?