Astonishing Science. Spectacular museum.
Create an ice balloon and explore how it melts.
Ideal for year groups: Reception – Year 6 (ages 3–11)
As an ice balloon melts students will use observation and questioning skills to examine the properties of ice. They will also test different factors and explore aesthetic aspects of the experience. This activity has scope for many cross-curricular links between art and science.
Ice balloon activity sheet
Download student activity sheet [pdf]
An iceberg is a frozen body of fresh water that is floating in salt water. Although icebergs may look quite small above the water line, they are much larger below the surface because of the differing densities of salt water and ice. As an iceberg melts it makes a fizzing sound as trapped air is released, which is sometimes jokily referred to as ‘bergy-seltzer’.
Students can see a real-life link to this investigation and the way that ice behaves when it is floating in water, e.g. when they have a drink with an ice cube in it.
Key Stage 1:
Ideas and evidence in science - Investigative skills:
Materials and their properties - Grouping materials and changing materials:
Key Stage 2:
Materials and their properties - Changing materials:
Water is one of the few materials that is less dense when it is a solid, which means that solid water (ice) will float. In much the same way that you only see the tip of an iceberg, when you put an ice balloon into water you can only see the top section of it. The part of it in contact with air melts at a different rate to the part submerged under water. This changes the shape of the balloon and shifts its centre of gravity. As the force acting on the centre of gravity shifts position this causes the balloon to move.
As you try out different things with your ice balloon you can see the effect on the melting process. Adding salt to ice will lower its melting point, making it melt a lot faster than ice where no salt has been added.
The bubbles of air within the ice balloon are formed when the water freezes and the air which is dissolved within the water is trapped within the ice balloon and takes the form of a bubble. This in turn changes the position at which gravity pulls on the balloon and causes it to move.
Ask a Scientist - The freezing point of sea water The Physical Society - Air bubbles in ice