The Lake Nyos Demo

Introduction

This is a fun demo that demonstrates differences in the density of gases. I show it to the students the day after they have done the What happened at Lake Nyos? Lab. The lab is available in a kit from WARD's Natural Science Establishment. Both the lab and/or this demo will fit nicely into a unit on density, water quality, or volcanism.

Materials shown in photo

clear plastic box or similar container, vinegar, baking soda, funnel, empty one gallon jug, 3 birthday candles (1 inch, 1.5 inch, and 2 inches tall)

Procedures

1. Position the candles in the bottom of the box as shown in the photo.

2. Put 1.5 cups of vinegar into the empty jug.

3. Using a funnel, add .25 cups of baking soda to the jug containing the vinegar. Let it set for about 30 seconds or so until the reaction has finished. In the meantime, light the candles.

4. Ask the students to predict what will happen as you pour the carbon dioxide gas into the plastic box near the end where the tall candle is. . . Since my students do the "What happened at Lake Nyos? Lab" on the previous day, they can predict that the candles will be "snuffed out", and they can predict which one will quit burning first , second, etc. Next, carefully pour the gas from the jug into the plastic box.

Since carbon dioxide is more dense than air, it fills the plastic box from the bottom up. . . just as water would. As a result, the shortest candle is snuffed out first even though it is farthest from the source of gas (jug). . . then the medium candle, and finally the tall candle. This is very similar to what happened near Lake Nyos in Africa, causing the deaths of about 1,700 people.