pH

What is pH? pH is the scale that tells you whether a substance is acidic, basic, or neutral. pH=“p” stands for power and “H” stands for hydrogen. The values correspond to the concentration of the hydronium ions.

What is an acid? An acid is a substance that donates hydrogen ions (H+) to form additional hydronium ions when dissolved in water. Therefore, there is a larger concentration of hydronium ions versus hydroxide ions. What is the formula for a Hydronium ion? Just add an H+ to water (H2O) = H3O+ (hydronium ion)

NaOH Sodium Hydroxide from the Penny Lab! What is a base? A base is a substance that either contains hydroxide ions or reacts with water to form additional hydroxide ions. Therefore, there is a larger concentration of hydroxide ions versus hydronium ions. What is the formula for a Hydroxide ion? Just take an H+ from water (H2O) = OH- There’s no HO’s in science!  Do you remember any compounds that had an OH? NaOH Sodium Hydroxide from the Penny Lab!

Properties: BASES Sour taste Can burn skin Contains more H3O+ than OH- ACIDS Sour taste Can burn skin Contains more H3O+ than OH- BASES Bitter taste Can burn skin Contains more OH- than H3O+ Feels slippery/soapy What is a common property of Acids and Bases? They both can burn!

The pH Scale… The pH scale ranges from 0-14. 0 = most acidic 7 = neutral (Distilled H2O) 14 = most basic But you can also have… Diluted acids= 3,4,5,6 on the pH scale and Diluted bases = 8,9,10,11 on the pH scale!

Diluted vs. Concentrated Diluted means to weaken with the addition of water. Concentrated means to strengthen with the absence of water. Think about when you made Kool-Aid and added too much water and what it tasted like. Too much water = it was too diluted = Does not taste good!

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pH Scale Concentrated acids Diluted acids Diluted Bases Concentrated bases acidic 0-6 basic 8-14 neutral 7 Diluted= weak Concentrated=strong

During the Lab… You will find the pH level using the pH probe. (take one place after the decimal point) Remember to dip the probe into the clean water BEFORE you dip it into the chemical! You will dip it in the substance for about 30 seconds and record the reading. You will Clean up any spills. Do not waste time talking. You will Hold on to the probe when it is in the beaker. You will Leave the pH probe at the table in the beaker of water! You will Move clockwise after 2 minutes / table.

Post-Lab Questions Which items were the is most acidic? Which items were the most basic? Which items on your scale were neutral? Which items on your scale were weakest acids? Which items on your scale were the weakest bases? Why would you take an antacid if your stomach was upset? 7. Label your pH scale with the 12different substances, according to the pH you found!

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Fill in pH Scale Lemon juice 2 Espsom salt 6 Antacid 8.5 Vinegar 3 Drain Cleaner 13.5 Vinegar 3 Espsom salt 6 Ammonia 11.5 Antacid 8.5 Water 7.6 Alcohol 7.9 Water 11 Soapy 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Coffee 5 Blood 7.4 Milk 6.9 Borax 8.5 HCl 1 Soda2.5 NaOH 14

Acids and Bases We can have weak acids and bases. Likewise, we can have strong acids and bases. Neutralize- to add an acid to a basic solution or a base to an acidic solution until it is chemically neutral or safe. (pH = 7). So…how would you neutralize a strong base like a laundry detergent spill on your skin? Pour large amounts of a weak acid on your skin like vinegar

Very Acidic Neutral Very Basic

So what’s wrong with Soda? Prolonged exposure to soft drinks can lead to significant enamel loss (tooth decay)! The erosive potential of colas is 10 times that of fruit juices in just the first three minutes of drinking!!!