the effects of carbon dioxide on the environment vanderbilt student volunteers for science...

13
The Effects of Carbon Dioxide on the Environment Vanderbilt Student Volunteers for Science Presentation Spring 2012

Upload: johnathan-norman

Post on 27-Dec-2015

220 views

Category:

Documents


3 download

TRANSCRIPT

Page 1: The Effects of Carbon Dioxide on the Environment Vanderbilt Student Volunteers for Science Presentation Spring 2012

The Effects of Carbon Dioxide on the Environment

Vanderbilt Student Volunteers for SciencePresentationSpring 2012

Page 2: The Effects of Carbon Dioxide on the Environment Vanderbilt Student Volunteers for Science Presentation Spring 2012

Safety

• The students should not handle the dry ice– You will be placing it in their cups for them

Page 3: The Effects of Carbon Dioxide on the Environment Vanderbilt Student Volunteers for Science Presentation Spring 2012

I. Introduction

• Discuss CO2 in the atmosphere• Explain the difference between acidified

rainwater and acid rain– Acidified = naturally dissolved CO2 (pH ~5.6-7)– Acid Rain = sulfuric acid, nitric acid, and others

causing a very low pH (<< 5.6)

Page 4: The Effects of Carbon Dioxide on the Environment Vanderbilt Student Volunteers for Science Presentation Spring 2012

II. Demonstration

• Discuss acids, bases, and indicators• Pour 3 cups 1/3 full each of: “rain water,” drinking

water, and “ocean water.”– Note: the “rain water” and “ocean water” are

synthetically prepared and have abnormal pHs so students can observe the color change

• One cup is basic, one neutral, and one acidic• Hand out color charts• Add some bromothymol blue to each cup to show

colors to students

Page 5: The Effects of Carbon Dioxide on the Environment Vanderbilt Student Volunteers for Science Presentation Spring 2012

IIIA. Experiment

• Pass out plates, cups w/ 1/3 ocean water• Students describe liquid, THEN add indicator• Go around and add 1 piece of dry ice to the

cups• Students observe

color changeSource:serc.carleton.edu

Basic Neutral Acidic

Page 6: The Effects of Carbon Dioxide on the Environment Vanderbilt Student Volunteers for Science Presentation Spring 2012

IIIB and IV. Explanation

• CO2 + H2O → H2CO3

– Bubbling CO2 in water makes carbonic acid• Why does ocean water start basic?– Dissolved minerals make it basic

• Why does the color change?– The indicator shows the water becoming acidic

due to the formation of carbonic acid• Discuss consequences of acidifying oceans

Page 7: The Effects of Carbon Dioxide on the Environment Vanderbilt Student Volunteers for Science Presentation Spring 2012

V. Effects of CO2 on Land

• Discuss what might happen with acidic rain• Tell students some CO2 dissolves naturally in rain water– Slightly acidic– This affects exposed rocks

• Rain trickles through soils– IMPORTANT: water gets most of its CO2 from soils where

CO2 partial pressure is 10-100 times that of the atmosphere. This is important for cave systems.

• Water is now more acidic and can dissolve calcite, the mineral in limestone

Page 8: The Effects of Carbon Dioxide on the Environment Vanderbilt Student Volunteers for Science Presentation Spring 2012

VI. Experiment – Limewater

• Pass out cups with 2/3 limewater• Drop 1 piece of dry ice in students cups– Have them observe the reactions– Cloudy in ~10 seconds, clear again in ~3 minutes

Page 9: The Effects of Carbon Dioxide on the Environment Vanderbilt Student Volunteers for Science Presentation Spring 2012

VI. (Cont.) Explanation

• CO2 dissolves after subliming

• CO2 reacts with Ca(OH)2 to form calcium carbonate (CaCO3)– Insoluble suspension, solution becomes cloudy

• Excess CO2 mixes with CaCO3 to form calcium bicarbonate (Ca(HCO3)2) which is soluble

• Solution becomes clear since the solid is no longer suspended in solution

Page 10: The Effects of Carbon Dioxide on the Environment Vanderbilt Student Volunteers for Science Presentation Spring 2012

VI. (Cont.) Cave Formation

• Reference the cave diagram while explaining:• Rainwater falls, dissolves CO2 in soils• Water percolates through limestone• Reacts with calcite (CaCO3) to dissolve it.– Leaves behind small cavities which grow over time

• Water moves elsewhere in the system– CO2 slowly exolves (leaves solution) converting

Ca(HCO3)2 → CaCO3 which is left as a solid– Cave formations such as stalactites/stalagmites

Page 11: The Effects of Carbon Dioxide on the Environment Vanderbilt Student Volunteers for Science Presentation Spring 2012

How do caves form? (flow chart)

Leaves behind tunnels

Caves Deposit formations

Form carbonic acid (H2CO3)

Seeps into bedrock Dissolves limestone

Rain falls and mixes with:

CO2 in atmosphere CO2 in soil

Page 12: The Effects of Carbon Dioxide on the Environment Vanderbilt Student Volunteers for Science Presentation Spring 2012
Page 13: The Effects of Carbon Dioxide on the Environment Vanderbilt Student Volunteers for Science Presentation Spring 2012