Ch. 6: Acids and Bases and Solutions

Lesson 1: Understanding Solutions

Vocab to know:

  • solvent- Dissolves other substances and is the part of a solution that usually is present in the largest amount
  • Water is the solvent when you make lemonade from a mix.
  • Water is known as the “universal” solvent
  • solute- the substance that is dissolved by the solvent. Can be gases, liquids or solids.
  • The lemonade mix is the solute that is dissolved in the water.
  1. Classification of Mixtures?
  2. Solutions
  3. Solution- a mixture containing a solvent and at least one solute and has the same properties throughout.
  4. solvent- Dissolves other substances and is the part of a solution that usually is present in the largest amount

*Water is the solvent when you make lemonade from a mix.

  1. Water is known as the “universal” solvent
  2. nutrients used by plants are dissolved in water
  3. Water is the solvent in blood, urine, saliva, sweat and tears.

b. Solvents can be gases, liquids or solids.

  1. solute- the substance that is dissolved by the solvent. Can be gases, liquids or solids.

*The lemonade mix is the solute that is dissolved in the water.

  1. Colloids
  2. colloid- a mixture containing small undissolved particles that do not settle out.
  3. The particles are too small to be seen without a microscope but large enough to scatter light.

* Many colloids are not clear because they scatter light.

  1. Fog is a colloid--made of water droplets in the air.
  2. solvent- air
  3. solute- water droplets that do not precipitate.
  4. fog scatters the head lights of cars, making it harder to see when in fog.
  1. other examples: milk, shaving cream, smoke
  1. Suspension
  2. Suspension- a mixture in which particles can be seen and easily separated by settling or filtration.
  3. Do not have the same properties throughout.
  4. Contains visible particles that can be easily separated.
  1. Formation of Solutions
  2. Solutions form when particles of the solute separate from each other and become surrounded by particles of the solvent.
  1. Ionic Solutes--such as NaCl dissolve in water because of the charges of the ions that make them up.
  • the positive and negative charges of the ions are attracted to the slight polar charges of the water molecules.
  • Water molecules will completely surround the NaCl and the solid crystals will dissolve completely in the water.
  1. Conductivity--ionic solutions conduct electricity because an electric charge is present.
  1. Molecular Solutes--such as table sugar break up into neutral molecules in the water. The covalent bonds holding the molecules together do not break.
  1. No conductivity most likely--no electric charge present means no electric current is possible.
  1. Effects of Solutes
  1. Raise the boiling point of a solution
  2. Salt added to boiling water will raise the temperature past 100˚ to about 104˚. (Without salt, the temperature of the boiling water cannot go above 100˚ )
  1. Lower the freezing point of a solution
  2. Salt added to liquid water will prevent it from freezing at 0˚. (Without salt, the temperature of the water molecules would slow down and crystallize into ice at 0˚ )

Lesson 2: Concentration and Solubility

  1. Dilute Solutions- have only a little amount of solute to a particular amount of solvent.
  1. Concentrated Solutions - have a lot of solute dissolved into a solvent.
  2. Changing concentrations
  3. add more solvent “water it down”
  4. remove solvent “thicken it up”
  5. Calculating concentrations
  6. Compare the amount of solute to the amount of the solvent.
  1. Solubility
  2. Solubility- The amount of a solute that can dissolve in a solvent at a particular temperature.
  1. Factors like pressure, temperature and the type of solvent will affect solubility.

**For example: Hot water will dissolve more sugar that cold

water.

  1. saturated solution- When no more solute will dissolve in a solvent

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  1. Solubility can be used to identify an unknown substance.
  1. Incompatible solutes and solvents cannot make a solution
  2. Oil and water--separate into layers as soon as you stop stirring
  3. water is polar
  4. Oil is non polar

Lesson 3: Acids and Bases

  1. Acids- compound that reacts with metals, tastes sour, and turns blue litmus paper red.

**important compounds in our lives

  • Folic acid--cell growth
  • Hydrochloric acid--digestion
  • Phosphoric acid--fertilizers
  • Sulfuric acid--batteries
  • Properties
  • React with most metals to form hydrogen gas-- acid seems to eat the metal away. Acids are called “corrosive” because of this.
  • Gold and platinum do not react with acids--
  • Acids are used to test the purity of fine jewelry. If a drop of acid reacts, then the metal is not pure.
  1. Reacts with carbonates to form carbon dioxide gas
  • seashells, eggshells, chalk, limestone
  • Sour taste--Never try to identify an acid by tasting it.
  • citric acid--citrus fruits like lemons and limes
  • acetic acid--vinegar
  • Reactions with indicators--litmus paper turns red
  1. Bases- compounds that taste bitter, feel slippery and turns red litmus paper blue

**Many uses

  • soaps
  • fertilizers
  • drain cleaners--can actually burn your skin!
  • Properties
  • Bitter Taste--never try to identify a base by tasting it.
  • tonic water-quinine, almonds, cocoa beans
  • Slippery feel
  • soaps and detergents and shampoos
  • Do not react with metals or carbonates to form carbon dioxide gas
  • Bases de-activate acids and vice versa
  • Acid indigestion--take an antacid like tums (base) and no more tummy trouble. Base neutralizes the acid by breaking the acid up and reorganizing it into gas and water molecules.