Intro to Biology
September 26, 2011
Lab Partners: Kristen, Tania and Betty
When using different methods to measure pH levels there are some tools that can be useful. Some more than others but by putting into action the different methods it may determine which tools will work best and give the best results when testing the pH within a solution. The pH, which stands for the proportion of hydrogen ions in a solution, could be acidic (acidosis), neutral or basic (alkaline). The pH scale goes from numbers 1 through 14. A pH of 7 is neutral; meaning the amount of hydrogen ions and hydroxide ions is equal, just like water. An acid is an ionic compound that gives off hydrogen ions into a solution. An ionic compound is the result of an ionic bond, which are formed after atoms transfer electrons to achieve full outermost energy levels or orbits. Bases are ionic compounds that give off hydroxide into a solution or accept hydrogen. Buffers are what keep them at bay by using weak acids to maintain the pH levels. By using a pH paper, indicator dyes and a pH meter, several tests will be conducted to check which one will result in a precise pH level reading.
Materials and Methods
Get 5 beakers and label them A through E. Fill the beakers with 20 to 25 milliliters of the appropriate solutions and then cut a piece of pH paper at least one inch in length. Dip the pH paper into the solution and color coordinate with the pH chart it provides.
Using indicator dyes.
Get 2 sets of test tubes and the label them A through E. Fill the tubes with equal amounts of solution and then in only the first set of tubes, place 2 drops of Bromothymol Blue dye into each and make sure it mixes in well with the solutions. On the second set of tubes do the same but this time place 2 drops of Phenolphthalein into the solutions.
Get 5 small beakers and label them A through E. Half fill the small beakers with the appropriate solution as it was done with the prior experiment but this time a pH meter and a cabbage extract called anthocyanin will be used. Before continuing, the pH meter needs to be calibrated. Once calibrated, measure the pH level of beaker A until the meter gives the result of the solution. Once finished with beaker A, place the sensor stick into water, wipe the stick by using a Kim-wipe before you could continue to beaker B. The washing of the sensor stick needs to be done before moving onto the next beaker for safety and to get an accurate reading. After testing all the beakers with the pH meter, add 2 drops of cabbage extract (anthocyanin) to each beaker and mix it well until there is a distinct color. By the pH reading that the pH meter provided, determine which solution from beakers A through E is a base or acid.
pH of household products.
Half fill 7 small beakers with Sprite, Vinegar, Dish detergent, Baking soda, Ammonia, Coke and Orange juice individually and equally measured. Place 2 drops of color extract (anthocyanin) in each beaker and make sure it mixes in well until there is a distinctive color. By comparing the colors to table 1 and 2 determine if the solutions are acidic, basic or neutral.
Fill 50 ml of distilled water into two small beakers. On one beaker, measure the distilled water with the pH meter and record the pH level. Carefully, added 1 drop of hydrochloric acid into the solution of distilled water until the pH dropped 1.0 pH unit on the pH meter. Then, I clean the pH meter sensor stick with water and a Kim-wipe. On the other beaker, place an Alka-Seltzer tablet into the solution of distilled water and let it sit until it fizzes out. Use the pH meter to measure the solution and recorded the initial pH reading. Next, gently swirl the beaker...