Sparkling Bubbles

Concept: A chemical reaction occurs producing hydrogen bubbles that are flammable.

Materials:

1000 mL beaker

250 mL side arm flask

3 test tubes

Long rubber tubing

12-15 pea sized foil balls

1 tsp. or 5 g NaOH pellets

Rubber stopper

Candle

Matches

Demonstration:

Pre-preparation: Fill 1000 mL beaker with about 900 mL of water. Fill 3 test tubes to the top with water and hold them upside down. Place them in the large beaker without getting any air bubbles in the beaker. Attach a rubber hose to the side arm of the 250 mL flask. Stick the other end of the rubber hose into the large beaker.

Place the NaOH pellets and foil balls into the 250 mL side arm flask. Add 10 mL water to the flask and quickly cover the top of the flask with the rubber stopper. Shake the bottle a little to get the reaction started.

Let the gas from the flask flow through the hose into the large beaker. Let the bubbles form in the water for about 30-40 seconds. This is to get rid of the mixture of air and hydrogen in the flask. Now put an upside down test tube over the gas tube. The gas will go into the tube and push the water out.

Have an assistant help you put a rubber stopper on test tube before removing it from the water. Fill the other two test tubes with hydrogen gas in a similar fashion.

Light the candle. While still holding the tube upside down, remove the stopper. Put the tube above the flame and hear what happens!

Introduction: How many of you like fire works? Today, I am going to do an experiment that sounds like fireworks.

Explanation: The aluminum foil in the presence of NaOH pellets reacts with water, producing hydrogen gas. As the gas rises from the flask, it travels through the tube to the beaker of water. Since hydrogen gas is less dense than water, it bubbles out of the water.

When producing a gas, more molecules are being made. The number of collisions the molecules make against their container makes pressure. Therefore, the more molecules made, the more collisions occur, creating a greater pressure. When the gas is fed into the upside down test tube, the bubbles of gas create a pressure which pushes the water out of the test tube.

The hydrogen gas now in the test tube is flammable. So when I hold the tube over the flame, the hydrogen gas ignites and creates a popping sound. It is like a tiny bomb or fireworks.

Al + NaOH ---> H2 + Al3+ + Na+

H2 + O2 ---> H2O + energy

Safety:

NaOH is a caustic hazard and should not get into eyes, mouth, or any skin. Wear goggles during the preparation since a pressure builds in the side arm flask and is a slight hazard.

Disposal: Any left over Aluminum foil should go in the waste can. The solutions can be rinsed down the drain.

Source: Public Domain