**Lesson 6.2: How is dissolved carbon dioxide and pH related?

REVIEW¶

Use our models from last class to give a brief review of what we discovered last lesson.

Oysters are dying because of ocean acidification, which is due to carbon emissions in the ocean.

2. Last class, what question(s) did we decide to prioritize investigating?

We decided to prioritize investigating the acidification of the ocean because it seems the most likely.

TODAY’S QUESTION/CHALLENGE¶

Why is answering today’s question important? How will it help us in determining what is happening to shellfish?

What makes something acidic or basic?

The concentration of hydroxide or hydrogen ions in a solution.

INVESTIGATION IDEAS¶

Record your ideas for investigations we could do in our class to determine if carbon dioxide is really going into the ocean. What are some ways that carbon dioxide is produced?

We could use Universal Indicators to identify if a solution is an acid or a base.

INVESTIGATING CARBON DIOXIDE AND WATER¶

Watch the following videos and complete the table.

Observations: What did you notice?

What does this tell us about the interaction of carbon dioxide and water?

Video #1 Acid w/BTB

It shows that when something becomes more acidic, the universal indicator turned yellow. In the case of btb, the indicator was already in the solution, so when the vinegar was dropped in the solution, it became yellow.

Video # 2

Breath w/BTB (stop at 0:22)

When the instructor breathed into the tube that led into the btb, it also turned yellow. This shows us that gaseous Carbon Dioxide can still be present in a liquid and increase the acidity of the liquid.

Video #3

CO2 over water no indicator

Even if the CO2 was going into the ocean, we wouldnt be able to tell because there was no change of visual properties. The water that was surrounded by CO2 looked exactly the same as before the experiment.

Video #4

CO2 over water w/BTB

Now that the water has BTB in it, it shows how much carbon dioxide actually went into the water. This shows that CO2 can combine with H2) even when one is a gas and the other is a Liquid.

SO WHAT?

What evidence shows that carbon dioxide is going from the air into the water and making it more acidic?

When Mrs Beck breathes into the water, the carbon dioxide goes into the water and the universal indicator indicates that it is becoming more acidic.

What ideas did we develop today that could be helpful for answering our questions? What else do we need to know about acidity?

We need to know what kinds of compounds are acids and what are bases. I sure wish that the next section would help me figure out which is which.

INVESTIGATING ACIDS AND BASES - Wear Safety Glasses!!¶

oh wow look at that, my wish came true!

Part 1: Known Aqueous Acids and Bases (acids and bases in a water solution)

Materials: Well plate, Pipette with solutions, pH paper, Safety glasses

Procedure:

Each group will have a well plate, pH papers and a pH tube with color charts to compare.
Place a drop or two of each aqueous solution (from up front) into your well plate.
Test the solution at your lab table with a small piece of pH paper.
Record the color, the numerical value of the pH strip and any other observations in the Data Table below.
After all of the listed substances have been tested, throw away your pH strips and rinse your well plate with water.
Wash hands and put away your googles.

Data Table:

Chemical Formula and Name	pH Strip COLOR	pH Strip NUMBER	Observations
\(NaOH\) [sodium hydroxide]	Dark Green	9.0	Basic
\(KOH\) [potassium hydroxide]	Dark Blue	11.0	Basic
\(HCl\) [hydrochloric acid]	Red	3.0	Acid
\(HC_{2}H_{3}O_{2}\) [acetic acid]	Orange	5.0	Acid
\(Ca(OH)_{2}\) [calcium hydroxide]	Dark Blue/Black	11.0	Basic
\(HNO3\) [nitric acid]	Very Red	1.0	Acid

What patterns are there in this data? Consider the testing results as well as the names and formulas in determining patterns.

words that have "acid" in them tend to be acids, and words with "Hydroxide" in them tend to be bases.

MEASURING ACIDITY¶

Read the article on pH about how acidity is measured.

What does the pH scale measure?

Power of Hydrogen

What is a logarithmic scale?

A scale that gets larger in bases of 10, or whatever base you specify.

What is the range of the pH scale?

The pH Scale can go from 0 to 14

Complete the following table on acids and bases.

	pH Range	Characteristics	THREE Examples
Acidic	0-6	Acids generally taste sour	HCl Cola Wine
Basic (alkaline)	8-14	Bases generally taste bitter	Soap Milk NaOH

MODELS¶

In the space below, update our model to show what we learned today about the interactions between carbon dioxide and water.

Carbon Dioxide and water react to form Carbonic Acid.

NEXT STEPS:¶

Reflect on today’s question: How is dissolved carbon dioxide and pH related?
Open up the IMT for this unit, complete all boxes for lesson 2 and make sure all parts of the L6.2 student sheet are complete.
Complete the L6.2 HW - pH reading guide then submit completed reading to schoology assignment post.**

Last update: June 5, 2023
Created: June 5, 2023