What's new

Bubbling bells

By David Shaw, 13 December 2018

Written by Elvina Lee

What’s the festive season without bells? Here’s an activity you can do, without the headache of excess jingling!

Safety: This activity uses small bells, which can be a choking hazard. Keep activity out of reach of children under the age of 3. Pour out water and safely pack away bells once the activity is complete.

You will need

• Round bells, 1 to 2 cm across
• Carbonated water
• Clear container, e.g. tall glass

What to do

1. Place the bells into the container.
2. Fill the container with carbonated water.
3. Watch the bells dance among the bubbles!

What’s happening?

The bells start at the bottom of the container as they are denser than water. Carbon dioxide gas is released from the carbonated water, forming bubbles around the bells. The gas bubbles are less dense than water, supporting the bells to float or become buoyant.

Once the bubbles around a bell pops, the bell is no longer supported. Being denser than water, the bell sinks back down to the bottom of the container.

Here are some questions for you to experiment with:

• What size bell floats to the top the most often?
• Would the bells still float in a different liquid?
• What other items can you use for this activity?

Did you know?

Pond skaters are small insects that walk on water. They have microscopic hairs on their legs that trap tiny air bubbles. The air is less dense than water, allowing these insects to stay afloat.

Microbubbles make pond skaters’ legs so buoyant they can support 15 times their own weight. But, if their legs get wet, pond skaters have a really hard time getting back to the water’s surface.

If you’re after more science activities for kids, subscribe to Double Helix magazine!