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Science Lab Experiment: Acid/Base/Neutral Solutions

Acids and bases

Purpose: To identify substances as acidic, basic or neutral solutions.

Materials: hydrochloric acid, HCl phenolphthalein sodium hydroxide, NaOH red and blue litmus paper distilled water bromothymol blue various substances watch glass glass rod droppers

Procedure: 1. Before doing any tests clean all glassware which you will be using. 2. Place a few drops of solution on a watch glass and test with litmus paper. Note the results in your data table. 3. Add one drop of phenolphthalein indicator and note the colour in your data table. Rinse the watch glass, add a few drops of solution a second time and test with one drop of bromothymol blue. Note results. 4. Rinse watch glass and glass rod and repeat the steps for all other substances.

Indicators: Litmus paper Red - acidic solution Blue - basic solution Phenolphthalein Clear - pH 0 to 8 Pink - pH 8 to 14 Bromothymol blue Yellow - pH 0 to 6 Green - pH 6 to 7.5 Blue - pH 7.5 to 14

Observations: see table.

Substance: Blue paper Red paper Phenolphthalein Bromothymol blue Acid, Base or Neutral pH < > or = 7 HCl NaOH Water Vinegar Lemon juice Baking soda Salt water Dish soap Javex Milk 7UP Fantastic Ca(OH)2 TUMS detergent

Questions: To include in your conclusion 1. What is an indicator ? 2. A few drops of an unknown solution are dropped onto a piece of red litmus paper and there is no colour change. a) The student concludes the solution is acidic. Is he correct? Explain. b) What could he/she do to verify his/her conclusion ?