Key Concepts

Carbon dioxide (CO2) gas dissolved in water can cause water to end up being acidic. The mountain of water from liquified CO2 have the right to be decreased by a base such together baking soda (sodium bicarbonate).

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The teacher blows into a global indicator solution until it transforms color. Students translate this color adjust and define that the equipment becomes acidic. Students explore whether carbon dioxide from other sources, specific carbonated water and also a chemistry reaction between baking soda and vinegar, can likewise make a equipment acidic. Students then apply their observations to the environmental problem of s acidification by doing research on this issue.


Students will be able to explain that carbon dioxide from any source reacts chemically with water to type carbonic acid. Lock will likewise be maybe to use the color changes of global indicator to monitor the changing pH that a solution throughout a chemistry reaction.


Download the student task sheet, and also distribute one per student once specified in the activity. The task sheet will certainly serve together the “Evaluate” ingredient of each 5-E class plan.


Be certain you and the student wear correctly fitting goggles during the task and wash hands afterwards. Universal indicator is alcohol-based and also flammable. Usage vinegar in a well-ventilated room. Read and follow all safety warnings top top the label. Dispose of all liquid waste down the drain or follow to regional regulations.

Materials for the Demonstration

Universal indicator solutionWater2 clean plastic cupsStraw

Materials because that Each Group

WaterUniversal indicator systems in cupUniversal indicator pH color chartCarbonated water (club soda or seltzer water) in wide, clear, plastic cupBaking soda in wide, clear, plastic cupVinegarAlka-Seltzer tablet2 little clear plastic cups4 vast clear plastic cups4 taller, clear, plastic cupsGraduated cylinderSnack-sized zip-closing plastic bag

About the Materials

For this lesson, each team will require a global Indicator pH color chart. Print sufficient pages of these charts ~ above a shade printer so the each group can have their very own chart. Friend may also choose to acquisition them indigenous Flinn Scientific, Product number AP8765.

Each group will also need global indicator solution, Flinn Product #U0002, and sodium bicarbonate (baking soda), Flinn Product #C0136 (500 grams).


Do a demonstrate to show that adding CO2 gas to water can make the water become acidic.

Materials for the Demonstration

Universal indicator solutionWater2 clean plastic cupsStraw

Teacher Preparation

Make indicator equipment for student groups

Make a dilute global indicator solution for this demonstration and for each student team by combining 625 mL water through 25 mL universal indicator solution.Pour at the very least 80 mL that this dilute universal indicator solution into a clean plastic cup because that each student group.

Note: Your local tap water is most likely fine because that the demonstration and tasks in this lesson. If the indicator systems you make is no green, this means that your water is either acidic or basic. If this happens, use distilled water, which is obtainable in supermarkets and pharmacies.

Note: In the activities, each team will require 80 mL that indicator solution. Inspect to make sure that girlfriend prepare sufficient solution. You will need about 50–60 mL of indicator solution for your demonstration. If 650 mL of systems is not enough, make much more using the same proportions.

Prepare because that the Demonstration

Pour about 25–30 mL the indicator solution into each of two clear plastic cup for you to usage in the demonstration.


Show students both samples of global indicator solution. Location a straw in one of the samples so the the straw goes every the method to the bottom that the cup.Explore

Have students usage club soda as a resource of CO2 to check out if the gas will adjust the pH of an indicator solution.

Question to Investigate

Will carbon dioxide native carbonated water change the pH of one indicator solution?

Materials because that Each Group

Universal indicator equipment in a plastic cupWaterCarbonated water (club soda or seltzer water) in a large clear plastic cup1 wide, clear, plastic cup2 taller, clear, plastic cupsGraduated cylinderUniversal Indicator pH color Chart

Teacher Preparation

Pour 25 mL that carbonated water right into a wide, clear, plastic cup because that each group.


Measure 30 mL of global indicator solution and also divide the evenly right into two small, clear, plastic cups. Include 25 mL the water to a large plastic cup and also 25 mL the carbonated water to another large cup.

Stand the little cups v indicator systems in the liquid in the wider cups together shown.

Turn the 2 tall cup upside down and also place them over the two broader cups.

While hold the top and bottom cup to store them together, tenderness swirl both sets of cups. Clock the shade of the indicator in both cup to view if over there is any change.

Compare the shade of the indicator come the pH shade Chart to uncover out whether the solution is acidic, neutral, or basic.

Expected Results

The indicator inside the cups with water stayed green, if the indicator with the carbonated water rotate yellow.

Discuss college student observations and what will happen in the complying with activity.

Ask students:

Did one of two people indicator change color?Only the indicator v the carbonated water readjusted color.What does the color adjust tell you about the pH the the indicator solution? Is that acidic or basic? The indicator systems is currently acidic. The carbonated water should not have splashed into the indicator. Why walk the indicator solution readjust color in one collection of cups?The carbon dioxide indigenous the carbonated water dissolved in the indicator solution. The molecules of carbon dioxide reacted through the water, developing carbonic acid, and changed the color of the indicator.

Tell students that they have actually seen carbon dioxide gas from your breath and carbon dioxide gas indigenous carbonated water revolve an indicator equipment acidic.

Ask students:

Do you think carbon dioxide gas produced during a chemistry reaction will also turn one indicator equipment acidic?Carbon dioxide native any source should cause the indicator equipment to end up being acidic. The amount of carbon dioxide gas produced and also dissolved in the indicator equipment may reason the shade of the indicator come vary, yet on the acidic side. What chemistry reaction do you recognize of that can develop carbon dioxide gas?Students should remember the vinegar and baking soda react, creating carbon dioxide gas. Phone call students that they will incorporate baking soda and also vinegar in the following activity.

Use a chemistry reaction to develop CO2 to see if it alters the pH of one indicator solution.

Question come Investigate

Will carbon dioxide gas developed in the baking soda and also vinegar reaction adjust the pH of one indicator solution?

Materials because that Each Group

Universal indicator equipment in cupUniversal indicator pH color chartWaterBaking soda in broad clear plastic cupVinegar in cup2 little clear plastic cups1 large clear plastic cups2 taller clean plastic cupsGraduated cylinder

Teacher Preparation

Pour about 50 mL the vinegar in a large plastic cup because that each group.Place around ½ teaspoon of baking soda into a tiny clear plastic cup for each group.


Measure and also pour 25ml of vinegar right into two large plastic cups. To water 15ml of global indicator right into two clean tiny plastic cups.Pour every the baking soda right into one that the cup of vinegar. Execute not to water anything into the other.

Stand the small cups with indicator systems in both that the broader cups together shown.

Turn the two tall cups upside down and also place them over the two wider cups.

While stop the top and also bottom cup to save them together, tenderness swirl both to adjust of cups. Clock the color of the indicator in both cups to view if over there is any type of change.

Compare the shade of the indicator come the pH shade Chart to uncover out whether the systems is acidic, neutral, or basic.

Expected Results

The indicator inside the cup with just vinegar remained environment-friendly while the indicator within the cup with the vinegar and also baking soda reaction turned yellow.

Discuss student observations.

Ask students:

Did either indicator change color?Only the indicator through the chemical reaction readjusted color. Why walk one collection of cups only have vinegar in the bottom?It is feasible that vinegar by itself reasons the indicator to change color. Due to the fact that this indicator did not change color, it must be the carbon dioxide gas developed by the chemical reaction, and not just the vinegar that caused the shade change. The indicator systems in the set of cup with just vinegar in the bottom serves as a control. What walk the color of the indicator systems tell you about the pH of each solution? Is the acidic, neutral, or basic?The color change shows that the indicator equipment is contempt acidic. What could you include to the acidic indicator systems to neutralize it?Because the indicator equipment is acidic, students have to suggest adding a base. Phone call students the baking soda is a base. Extend

Explain how ocean acidification is negative for shell-making organisms and also show a video clip about s acidification.

Explain the the ocean is in reality basic. The pH the the ocean is about 8.2. The hatchet “ocean acidification” way that the ocean is tending come become an ext acidic or much less basic. It has actually moved from about 8.2 to 8.1. This may not seem prefer a large change but it is a very large change to biology in the s which are really sensitive to transforms in pH. When ocean water becomes more acidic it reasons two main problems for shell-making organisms favor clams, oysters, and coral:

It i do not care harder for these organisms to do their shells

Have students carry out research on methods to mitigate the lot of carbon dioxide released into the atmosphere.

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The vast bulk of the overfill carbon dioxide in Earth’s atmosphere is from burning fossil fuel such as petroleum, herbal gas, and also coal. Many of this fuel is supplied for cars, trucks and also other creates of transportation, for running power plants that produce electricity, and also for heating homes and also businesses.

Have students research alternative sources of power that could help in burning less fossil fuel. Students could present their research in a short file with illustrations, power point, tri-fold board, or in any method you feel will certainly work. College student should define how the renewable energy source works and the benefits and obstacles of the technology.