Acids and Bases Indicator Lab

Acids and Bases Indicator Lab Purpose: 1. To discover properties of acids and bases 2. To develop methods for identifying acids & bases Materials:  2 microplates  Safety goggles  0.1M HCl  0.1M NaOH  4 unknown solutions (A – D)  4 House hold solutions  Data booklet 3. To classify unknown solutions as acids or ba  Various indicators  Red and blue litmus paper  Bromothymol blue  Phenolphthalein  Methyl orange  Magnesium Procedure: PART ONE: Acid and Base 1. Place 1 – 2 drops of phenolphthalein indicator into one microwell. 2. Place 1 – 2 drops of bromothymol blue indicator into one microwell. 3. Place 1 – 2 drops of methyl orange indicator into one microwell. 4. Place one small piece of red litmus paper into one microwell. 5. Place one small piece of blue litmus paper into one microwell. 6. Place one small piece of magnesium into one microwell. 7. Add 5 drops of hydrochloric acids into each microwell containing an indicator. Record your observations in Table 1. 8. Repeat steps #1 – 6. 9. Add 5 drops of sodium hydroxide (NaOH) into each microwell containing an indicator. Record your results in Table 1. 10. Remove the magnesium and litmus paper using tweezers; wash and dry your microplate. PART TWO: Identifying Unknown Solutions 1. Place 1 – 2 drops of phenolphthalein indicator into one microwell. 2. Place 1 – 2 drops of bromothymol blue indicator into one microwell. 3. Place 1 – 2 drops of methyl orange indicator into one microwell. 4. Place one small piece of red litmus paper into one microwell. 5. Place one small piece of blue litmus paper into one microwell. 6. Place one small piece of magnesium into one microwell. 7. Add 5 drops of Unknown A into each microwell containing an indicator. Record your results in Table 2. 8. Repeat steps 1 – 5 for Unknown B – H. 9. Wash and dry your microplate. Observations: Table 1: Acid and Base: Indicator Observations Phenolphthalein Acid 0.1 M HCl Stayed the same Base 0.1M NaOH Stared off clear, turned purple instantly when NaOH was added Stayed blue Bromothymol blue Slowly turned yellow, started off blue Methyl orange Went red and started as orange Started as a dark orange, turned light orange Red litmus Stayed the same Started off as a light pink, turned blue Blue litmus Turned red from blue Stayed the same Magnesium metal Nothing happened Stayed the same Table 2: Identifying Unknowns and House Hold Solutions Indicator A Did nothing B Did nothing Started off as clear, turned magenta Turned to a lighter blue Stayed the same Started off as blue, turned yellow Stayed blue Turned to a lighter orange Stayed the same Stayed the same Stayed the same Started off orange, turned red Stayed red Turned orange Milk of Magnesia Turned a little bit purple, pushed phenophtj alein outside Turned Milk yellow stayed in middle pushing liquid out, stayed blue Turned red Turned yellow Turned blue Turned blue Stayed the Turned same blue Turned red Stayed the same Phenolphthalein Started off blue turned Bromothymol blue yellow Methyl orange Red litmus Blue litmus Started off orange, turned red Stayed the same Started off blue, turned red C Observations D Oven Cleaner Stayed the Turned same magenta Turned blue Turned darker blue Turned red Lemon Juice Stayed the same Cola Did nothing Turned yellow Turned red Stayed red Turned red Magnesium metal Acid, Base or Neutral? Had a reaction with the substance added and bubbled and fizzed. Acid Stayed the same Nothing Had a happened reaction with the substance and sizzled. Stayed the same Bubbling a little bit Nothing happened Bubbled up Neutral Base Base Acid Base Acid Acid Discussion: 1) List the solutions in Part B in order from most acidic to least acidic. A, D, Cola, acid juice 2) Which unknown solutions was neutral? Explain how you know. Unknown solution B was neutral because no reaction occurred, and the indicators stayed the same. 3) Which acid/base indicator do you think would be the most useful? Explain. Methyl Orange would be the most useful indicator because it clearly showed the changing of acids or bases. 4) Which acid/base indicator do you think would be the least useful? Explain. The magnesium metal was the least useful reaction because it barely reacted and it would not be able to show you if the solution was neutral or a base because it doesn’t react for either. 5) If you add a clear unknown solution to phenolphthalein and it remains clear, what are two possibilities for the pH of the solution? The two possibilities for the solution would be a base or neutral. 6) If you add a clear unknown solution to bromothymol blue and it stays blue what are two possibilities? The two possibilities would be a base or neutral. 7) Suppose you were asked to put together a test kits to determine whether water taken from a factory waste drain is acidic, basic or neutral. Your kit can only contain three tests. Which tests would your kit contain? Explain. The three indicators chosen for the kit would be methyl orange, the red litmus paper and the magnesium metal. The reason for the magnesium is because it usually reacts to acids, so if the water was acidic, it would be identified. The reason for the methyl orange is because it is the strongest indicator for acids and the reason for the red litmus paper is because it always reacts to bases so if the water was basic, then it would Identify that. The red litmus paper could also identify if it was neutral because there would be no reaction. Conclusion: This experiment investigated the properties of acids and bases, and classifying unknown solutions as acids or bases. In order to study the problem, students went into groups of four and were asked to classify whether hydrochloric acid and sodium hydroxide were acids or bases using different indicators. The indicators students used were phenolphthalein, bromothymol blue, methyl orange, red and blue litmus paper, and magnesium metal. Students put the sodium hydroxide and the hydrochloric acid into microwells that had a different indicator in each one. After, students recorded the observations of the reactions. Next, students were given unknown substances and were asked to test each substance with all the indicators and figure out if it was acids or bases. Students tested unknown substances A-B with the 6 different indicators and recorded all the observations in a chart. The last substances students were asked to test was oven cleaner, lemon juice, milk of magnesia, and cola. Students did the same thing as the other substances, using the same indicators and recorded the observations down. Results showed that in the first part of the experiment the 0.1m of HCl reacted in the Bromothymol blue, turning it yellow, and in the Methyl orange, turning it red. The HCl also turned the blue litmus paper red. The other 0.1m of NaOH students tested turned the phenolphthalein purple instantly, and the red litmus blue, either then that everything else stayed the same. In part B, students identified the unknown substance A and substance D as an acid as it turned the bromothymol blue yellow, and the methyl orange red, and the blue litmus red. It also made the magnesium metal fizz and bubble. Results also showed that the unknown substance B was identified as neutral because none of the indicators reacted to the substance. Unknown substance C was identified as a base as it turned the indicator phenolphthalein purple, and the red litmus blue. Students figured out that the oven cleaner and the milk of magnesia were both bases. Both substances were concluded as bases because both turned the phenolphthalein magenta and the red litmus paper blue. The lemon juice and cola were concluded to be bases. Both substances reacted with the bromothymol blue, turning it yellow, and reacted with the methyl orange, turning it red. The lemon juice and the cola also turned the blue litmus paper red, and made the magnesium metal fizz and bubble. The purpose of using indicators is to make it easier to identify whether a substance is an acid or base. There are many different types of indicators, which are helpful to back up each indication to prove that it is either an acid or base. Knowing whether something is an acid or base is important because acids can react to certain substances and it could be dangerous. To extend this experiment, a few different things could have been done. Students could have compared the time it takes for reactions to occur between acids and bases. Another way to extend this experiment, students could have tried more types of acids and bases with the indicators and tried to figure out what acid had the biggest and fastest reaction to each indicator. Either than that, not much more could have been done to extend it. Questions about the experiment include; Why do acids and bases react to different types of indicators? Also, how do acids and bases react to the indicators. One last final question is, how are the indicators made? Possible errors in this lab could have occurred when we were adding in the substances, we may have added too much in. Finally, if the experiment was repeated, some changes to improve the experimental design could be to use more exact measures of the substances and of the indicators. Students could also compare the outcomes from the experiment with other groups. Acid Base Lab – Self assess prior to handing in Just starting out… Observations Completion/ Questions Conclusion / Reflection / Big Ideas Lab Technique In Progress Getting there Got it Rock Star  Data tables are completed. All data is clearly recorded  Ideas demonstrate thoughtful thinking  All questions are complete and well-explained  Student shows exceptional ability to sum up the big ideas of the lab activity  Student can describe the purpose and specifically report his/her findings  Detailed yet concise  Student has demonstrated reflection on the activity, addresses possible errors made during lab activity and improvements for future tests  Student can follow procedures and work with group effectively  Student follows lab safety expectations: wears goggles, hair up, handles glassware appropriately, on task at all times  Lab station (including desk surface), supplies, sink, and chemicals are all cleaned up and put away accordingly