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Indicators and pH To learn about pH and how indicators show a substance to be an acid or a base. Objective:

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Presentation on theme: "Indicators and pH To learn about pH and how indicators show a substance to be an acid or a base. Objective:"— Presentation transcript:

1 Indicators and pH To learn about pH and how indicators show a substance to be an acid or a base. Objective:

2 Research: Acid: solutions – high concentration of H 3 O + ions. Hydronium Base: solutions – high concentration of OH - ions. Hydroxyl pH: percent of hydrogen – how acidic it is.

3 pH scale: series of numbers = neutral, 0-6 acid, 8-14 base. Indicator: substance that shows a definite color change when mixed with acid or base.

4 Effect on Acids Effect on Bases Blue litmus paper: pink ___ Red litmus paper: ___ blue Phenolphthalein: stays clearshocking pink Bromthymol blue: orange ___ Congo red: blue ___ As the pH of a solution changes, the indicator shows a specific color change.

5 Procedure I – Acid After each step, record your observations. Drop a small drop of HCl onto blue litmus paper. Drop a small drop of HCl onto red litmus paper. Place a small amount of HCl into test tube A. Add 1 drop of phenolphthalein. Rinse TT. Place a small amount of HCl into test tube A. Add 2 drops of bromthymol blue. Rinse TT. Place a small amount of HCl into test tube A. Add 1 drop of congo red. Rinse TT.

6 Procedure II – Base After each step, record your observations. Drop a small drop of NaOH onto blue litmus paper. Drop a small drop of NaOH onto red litmus paper. Place a small amount of NaOH into test tube B. Add 1 drop of phenolphthalein. Rinse TT. Place a small amount of NaOH into test tube B. Add 1 drop of bromthymol blue. Rinse TT. Place a small amount of NaOH into test tube B. Add 1 drop of congo red. Rinse TT.

7 Reaction withAcidBase Blue litmus paper Red litmus paper Phenolphthalein Bromthymol blue Congo red


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