2 pHLiving things have certain pH ranges for normal biochemical processes to occur.pH is a logarithmic scale for measuring acids and bases videoMeasured through indicators or pH meter
3 Properties of Acids & Bases Taste tart or sourConduct electricityHave more hydronium ionsH3O+Base (Alkaline)Taste bitterFeel slipperyHave more hydroxide ionsOH-Buffers are chemicals that neutralize the effects of adding small amounts of either an acid or a base to a solution.
4 Strongest acidWeak acidIf “Normal rain water” is pH 6, then what would the pH of acid rain be?NeutralWeak BaseStrongest base
5 SAFETY NO tasting, smelling, touching of liquids NO tasting, smelling of papersNO wandering – be aware while cleaning up.Everyone wears goggles to protect eyes from splashesOne person from team wears gloves while handling materialsFirst Aid – wash affected area with plenty of water.
6 CLEANUPUse toothpicks to remove pH paper. Throw toothpicks and pH paper in white barrel near sinkPour contents of Chemplate into the BEIGE water basinDip the Chemplate into the GREEN bucket 5xRinse Chemplate out in RUNNING waterLeave Chemplate on counter
7 Data Table Create a data table to account for: Material tested (6 items)Cavity number (#)Original colorColor change for acid (HCl)Color change for base (NaOH)
8 Lab Setup Setup the Chemplate as follows: Phenol red: one drop in cavities 1 and 2Phenolphthalein: one drop in cavities 5 and 6Bromthymol Blue: one drop in cavities 9 and 10Red litmus paper: ¼” square in cavities 3 & 4Blue litmus paper: ¼” square in cavities 7 & 8Universal pH Indicator paper: ¼” square in cavities 11 & 12
9 Lab ProcedureAdd one drop of dilute Hydrochloric Acid (HCl) to cavities 1,5, and 9. Stir with toothpick.Add one drop of dilute Sodium Hydroxide (NaOH), a base to cavities 2,6, and 10. Stir with toothpick.Record data into table.For paper strips in cavities 3 and 7 add one drop of HCl. Record data into table.For paper strips in cavities 4 and 8 add one drop of NaOH. Record data into table.Cavity 11 – 1 drop of HCl; Cavity 12 – 1 drop of NaOH. Compare color to pH scale on vial.
10 Post Lab Questions How do you think litmus paper is made? Of what value is Universal pH Indicator paper?How do you think Universal pH Indicator paper is made?A student pH tests several items and is asked to place the results in order of strongest acid to weakest acid. What should the results look like? Values are 6.7, 7.0, 3.5, 4.2, 8.9, 2.0, and 13.Add to your notes – What color do acids turn blue litmus paper? Red litmus paper? What color do bases turn blue litmus paper? Red litmus paper?
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