Volcanic gas

Need samples of Pumice, Scoria, and tuff

• Many volcanic samples are full of holes. Some samples of pumice are so full of holes that they will float on water. What puts these holes in the rock?

Objective

• To understand something about gases in a volcano, we will examine something we know a little better and can work with safely, soda.

• the eruption of a volcano is like opening a soda. We will use this model to help us understand the relationship between the gases and the volcanoes.

Effects of fumes

• When you read the descriptions of volcanic eruptions you learned that gases flowing down the sides of the volcanoes were very destructive. They were very hot and poisonous. When tourists visit Volcanoes National Park in Hawaii, they find signs warning them of the toxic fumes coming from vents around the park, even in the camp grounds.

Question

1. What makes a soda taste “fizzy”?2. What do you hear when you open a can or

bottle of soda?3. What is the cause of this sound?4. Why does this happen?5. If you open a soda and leave it out overnight,

will it taste “fizzy” the next day?

Materials• List• One bottle of soda (20 oz or

smaller)*• Rubber tubing (about 50 cm)• 1-L or 2-L Erlenmeyer flask• Plastic tub (shoe box sized)• Size 3 rubber stopper with barb

connector to fit the tubing• Laboratory stand with 9 cm (id)

ring*• Beaker large enough to hold the

bottle.*• Hot water*• Water*

• Picture

Procedure

• Form into group

• Each group gathers the needed materials• Record the volume of your soda container in

your journal.• Each person predicts the amount of CO2 gas

stored within the bottle of soda (ranges are given on the next page

How much carbon dioxide gas is in a small soda?

1. 1 - 100 cm3

2. 100 - 1,000 cm3

3. 1,000 - 10,000 cm3

4. Over 10,000 cm3

Procedure

1. Put on your safety goggles.2. Fill flask with water even

with its lip.3. Open the clamp on the ring

until it slides easily over the post on the lab stand.

4. Place the ring over the mouth of the flask.

Procedure

5. Put about 1 L of water in the plastic tub.

6. Place the tub on the base of the laboratory stand.

7. Place one hand securely over the mouth of the flask and tip it up side down. Do not remove your hand until you and your partner have completed step 8.

8. Slide the clamp over the post on the lab stand and lower the flask until the mouth of the flask is completely submerged in the water in the tub. There should be room for the hand under the flask without raising it above the level of the water.

Procedure

9. Tighten the clamp to support the flask.

10. Remove the hand from the mouth of the flask.11. If there is any air in the flask, record the amount. Approximate

if you cannot measure the amount precisely.

Procedure12. Slide one end of the rubber

tubing under the mouth of the flask. If it will not stay there, carefully lower the ring until the flask holds the tubing in place. Steady the flask as the ring is lowered.

13. Prepare the other end of the tubing by putting the barb in the tubing.

14. Get ready with the stopper end of the tubing. While one person opens the soda, the other should quickly seal the opening with the stopper.

15. Stand the bottle in the beaker and pour hot water around it.

16. If gas release slows, swirl the bottle to agitate the liquid

Observations

• Look at the flask. Record your observations in your journal.

Post-lab questions

1. What volume of gas was released from your soda?2. How does the volume of gas released compare to

your hypothesis?3. How do you account for any differences?4. Why is it important to heat and agitate the soda?5. What is the gas you have liberated from the soda?6. How does this activity model what happens in a

volcano? 7. How is this model unlike a volcano?

Making Sense• The parallels we want them to see are that the gases in

volcanoes are under extreme pressure. As they work their way to the surface, pockets of gas expand just as bubbles in a pot of boiling water expand as they get closer to the surface. The particles, themselves, don’t change, but the space between them increases. This is due to the reduction in pressure on them. Just as they cannot see the gas dissolved in a bottle of soda while it is capped, the gases are trapped under pressure in the volcano. When the volcano erupts, it is like opening the soda – the gases are released and the compressed bubbles expand rapidly.

• Because gas is less soluble as temperature rises, we place the soda in hot water to release the gas faster. Remind them of the relationship between dissolved gases and temperature. Volcanoes are very hot, so the gases are more likely to be released. Volcanic eruptions are frequently accompanied by earthquakes as the magma moves around in the magma chamber. Relate this to the swirling of the bottle.

• Rapidly released hot gases such as carbon dioxide and sulfur dioxide are more dense than air. They travel rapidly down the mountain sides of the volcanoes, scorching and killing whatever is in their path. This cloud of hot poisonous gas is called a nuée ardente – a glowing cloud. This was described in the story of Mount Pelée. It was a major factor in the deaths at Pompeii and Hurculaneum.

• The soda contains only carbon dioxide. Volcanoes contain water vapor, carbon dioxide, and sulfur dioxide. See the reading on page G-40.

Effects of Gas released from a volcano

• Sometimes only gases are released from a volcano, with no other materials. Lake Nyos, in Camroon, is actually an ancient caldera. When carbon dioxide gas trapped at the bottom of the lake was suddenly released, the result was a disaster in the area around the lake.

• The story can be read at http://www.smithsonianmag.com/science-nature/killerlakes.html?c=y&page=1

The sulfur combines with moisture in people’s lungs to form acid. Too much

exposure is deadly

What happens when you shake up a soda and then remove the cap?

• Why do a lot of people burp after quickly drinking a can of soda?