ACIDS & BASESJen Rosenthal

WHAT DO YOU ALREADY KNOW ABOUT ACIDS & BASES?

Where might you find them? Are all acids & bases harmful? What foods do we eat or drink that may be acids/bases? How can we tell the difference between them?

COMMON PROPERTIES OF ACIDS & BASES

AcidsTaste sour, are corrosive to metals, change litmus (a dye extracted from lichens) red, and become less acidic when mixed with bases.

BasesFeel slippery, change litmus blue, and become less basic when mixed with acids.

DEFINING ACIDS & BASESArrehenius (1800s):Described the difference between Acids & Bases

in this way:Acids: Release hydrogen ions (H+) in water

Bases: Release hydroxide ions (OH-) in water

BRONSTED- LOWRY MODELAcids: any substance that can DONATE a

hydrogen ion (H+). They INCREASE the concentation of H+ ions in solution by donating them.

Ex: HCl (strong acid)

Bases: any substance that can ACCEPT a hydrogen ion (H+). They DECREASE the concentration of H+ ions in solution by accepting them.

Ex: NaOH (strong base)

NEUTRALIZATIONWhen an acid & base are mixed you form

a salt and water.

Ex: HCl + NaOH H2O + NaCl (s)

Acid + Base water + salt (any salt)

PHA representation of the

concentration of H+ ions in solution. pH = -log [H+]

For example: [H+] = 1x10-7 moles/liter = pH of 7which would be considered NEUTRAL

ACTIVITY: INDICATORS FOR INQUIRYFollows the 5 Es to Inquiry1. Engage2. Explore3. Explain4. Elaborate5. Evaluation

MATERIALSIndicator Solutions: Substances to

Test:- Red cabbage juice - Baking Soda- Radish juice - Soda- Cherry juice - Lemon juice- Blueberry juice - Lime juice- Beet juice - shampoo- Carrot juice - Dishsoap * Others that you would like to tryOther solutions to be used:Vinegar, distilled water, & dilute ammonia

PART I. INVESTIGATING INDICATORSIndicator(10-20 drops)

Acid (Vinegar)40-60 drops or 1-2 mL

Base (Ammonia)40-60 drops or 1-2 mL

Neutral(Distilled Water)40-60 drops or 1-2 mL

PART II. TITRATIONInstructions.

1. Begin with 2 mL of vinegar in a cup or test tube.

2. Select an indicator from those tested (one group should select red cabbage juice)

3. Add about 10 drops (0.5 mL) of indicator to the beginning vinegar solution.

4. Begin to add one drop at a time of ammonia to the indicator/vinegar solution. Note the color change of the solution as you continue adding drops.

5. Repeat the procedure this time using ammonia as the base solution with the indicator and add vinegar slowly observing the color change.

TITRATION RESULTSVinegar + Indicator Ammonia + Indicator

PART III. TESTING HOUSEHOLD CHEMICALSHousehold Substance

Vinegar Test Ammonia Test

Water Test Results

PART IV. AQUARIUM TESTScenario: Something has contaminated

the aquarium water. You will be given a water sample and asked to determine if it was acidic or basic, based upon your prior tests.

WHAT IS INSIDE OF RED CABBAGE?Flavin (an anthocyanin) water-soluble

pigment that is also found in apple skins, grapes, plums, poppies, & cornflowers.

Acid solutions Turn REDBasic solutions Turn BLUE/GREENNeutral solutions Remain PURPLE

CABBAGE JUICE INDICATOR

ACID NEUTRAL BASE (RED) (PURPLE) (BLUE)