Common Foods and the pH Scale

Background:

Acids and Bases

The Bronsted-Lowry definition of acids is that acids are compounds that give off H+ ions when they react with another compound. Likewise, this definition says that bases are compounds that accept H+ ions from other compounds.

The Arrhenius definition of acids says that they’re compounds that give off H+ ions in water and that bases are compounds that give off OH- ions in water.

These definitions are the same. Basically, if you have something that can give off H+ in water it’s and acid. As a result, all acids have hydrogen atoms on them that are ready to leave in water. Most common acids have the letter H in the beginning of them: hydrochloric acid, hydrobromic acid, hydroiodic acid, etc. Bases, on the other hand, are compounds that give off OH- in water. (The two definitions of a base are identical, as OH- combines with H+ to form water). When you see the formula of a base, it has “OH” in it: NaOH; Sodium Hydroxide, LiOH; Lithium Hydroxide, and KOH; Potassium Hydroxide.

You can also define acids and bases as being “strong” or “weak”. Strong compounds are compounds that completely break up in water. In other words, if we are talking about a strong acid, all of the H+ ions break away from the molecule in water. For strong bases, all of the OH- ions break way from the molecule in water.

There is a difference between a "strong" acid and a "reactive" one. Strong acids are all reactive, but some "weak" acids can also be extremely reactive. A good example of a weak, reactive acid is hydrofluoric acid, HF. Even though it's a weak acid, it can cause an explosion resulting in serious and permanent injury if caution is not used.

Examples of Acids Formula | Name | Strong/Weak | HCl | Hydrochloric Acid | Strong | HBr | Hydrobromic Acid | Strong | Hl | Hydroiodic Acid | Strong | HF | Hydroflouric Acid | Weak | HNO3 | Nitric Acid | Strong | H2SO4 | Sulfuric Acid | Strong | H3PO4 | Phosphoric Acid | Weak | CH3COOH | Acetic Acid | Weak |

Examples of Bases Formula | Name | Strong/Weak | NaOH | Sodium Hydroxide | Strong | LiOH | Lithium Hydroxide | Strong | KOH | Potassium Hydroxide | Strong | Mg(OH)2 | Magnesium Hydroxide | Weak | Ca(OH)2 | Calcium Hydroxide | Weak | NH3 (NH4OH) | Ammonia/(Ammonium Hydroxide) | Weak |

Properties of Acids and Bases
Properties of acids include: * React with most metals to form hydrogen gas * Tastes sour (like lemons) * Frequently feel “sticky” * Usually gases or liquids

Properties of bases include: * Feel “slippery (The slippery feeling is because the skin dissolves a little when touching the base) * Taste bitter (like baking soda) * React with oils and greases * Frequently solids (ammonia is a gas that’s usually dissolve in water) pH Every water-based solution will have a pH that is acidic, basic, or perhaps neutral. PH is a measurement that is used to quantify aqueous solutions into a range of values known as the pH scale. If the solution is basic it will be higher on the scale, if it is acidic it will be lower on the scale.
Because of the acid base relationship, whenever the concentration of one ion in an aqueous solution is known, the other ion concentration can be deduced. OH- and H+ concentrations are measured on a logarithmic pH scale. The formula for pH is written -log [H+]. pH is calculated by using the negative logarithm (base 10) of the H= concentration.
PH values below 7 are considered acidic, and values above 7 are considered basic. A pH between 6 and 8 is the range observed for most biological fluids.
Question:
Where do our most common selections range on the pH scale?
Hypothesis:
We hypothesized that people don’t consume basic foods or liquids.
Materials:
Six solid foods: 1 Lemon, 2 slices red apple, 1 slice of green pepper, 1 Vienna chicken sausage, 1 tomato, and 1 green grape.
Six Liquids; 2oz of each: