Adapted from www.us-ocb.org
Sue Boudreau 4.29.2011
Explore what’s acid, what’s basic, how to measure it and how acidity is related to the future of life in the oceans.
1. What does ‘acid’ mean a. to you BEFORE instruction: b. AFTER the lab and reading chapter 9.2:
2. What does a ‘base’ or ‘alkalai’ mean a. to you BEFORE instruction: b. AFTER the lab and reading chapter 9.2:
3. How are acids and bases important in our lives (our bodies, the stuff we buy and rely on) and the life on the planet? a. BEFORE instruction: b. AFTER the lab, video clip and chapter 9.2:
4. AFTER the the lab and reading: How is the strength of an acid or base measured? Give the methods, the scale and how it works.

You will be comparing the acidity of tap water and sea water to a whole variety of chemicals using universal indicator.
The strength of an acid is measured by the concentration of hydronium ions in the solution (H3O+). pH is a measure of the concentration of hydronium ions in the solution. pH 7 is neutral and green with universal indicator. Strong acids are red (pH 1-3), weak acids are 4-6.9, pH 7 is green and neutral, ph 7.1 and above are bases and go blue through to purple. See p.403 for a color chart.
1. Note ways to prevent CROSS CONTAMINATION of your results:
2. Note/sketch how you will KEEP TRACK of what you are testing in the SEPUP trays:
3. Note SAFETY precuations:
4. Draw a data table on graph paper to record pH prediction, color it goes with ‘universal indicator’ and actual pH for each of the solutions at the front. (List the variables you have to record, try different ways of organizing your data table on scratch paper. Then draw it out below using a ruler. Make it clear and easy to use!)
5. Analysis
1. Which solution was most acidic? _____________________________pH_______
2. Which solution was most basic? _____________________________pH_______
3. Rank the waters (seawater, tap water, distilled water, seltzer water) from most basic to most acidic:
4. What result surprised you most during this experiment and why?
5. What household fluid was most like seltzer water?
6. What does seltzer water have to do with ocean acidification?
7. Tap water comes from river water. What pH will freshwater life do best in? _____________
8. What pH will sea life do best in? __________
9. Finish the AFTER parts of the questions at the start of the activity.

Teacher Notes:
MATERIALS
Gather a range of kitchen and household chemicals from acid to base. Include soda water, “instant ocean”
(1/2C to 1 gallon of distilled water. Get from aquarium suppliers), distilled water and tap water.
Each team needs 4 clipboards, 4 eye protectors, 4 SEPUP trays, 1 universal indicator bottle with a dropper just for the indicator. A sheet of graph paper each for making data tables.
Class organization:
Label beakers for each solution and put in two droppers. Set up the original container + the beaker on plates. I did 4 solutions per small coffee table. Scattered the 4 coffee tables so kids could get to all sides easily.
Suggested they each have their own SEPUP tray and split up the solutions so each kid goes to a different coffee table. Works really fast that way. They have to figure out how to keep track of what they are testing.
Safety:
Trip hazards, hair, sleeves. Eye wash station. Wash hands after. Don’t taste or drink anything.
Cross-contamination control:
Don’t mix up the droppers in the different solutions. Don’t touch the universal indicator dropper to any of the solutions.
Management:
Show students how to measure pH using p.403 in the text. Have them practice a little.
Let them figure out their own data tables. Then show kids who struggle how before they start.
Extension can be to repeat with different indicators. We have bromothymol blue and phenolpthalien.