In this experiment we will learn
- How to make Ice balloons?
- How the phase change occurs from ice to liquid water?
- How does the salt affect the melting of an ice ball?
Materials Required (What Do I Need?)
- 1 small balloon (try to get a small size balloon so that the water inside it will freeze quickly)
- Access to freezer
- A plastic tub to catch melting water
- A transparent plastic tub filled with some water
- Food coloring
Procedure (What to do?)
- Stretch the balloon and attach it to the water tap mouth and slowly fill the balloon with water.
- Carefully remove the air from the balloon and tie a balloon knot.
- Now put the balloon in a freezer for at least 2 days.
- After 2 days, when the water inside the balloons is frozen completely, take them out in the plastic tub.
- Cut the neck of the ice balloon and peel off the balloon.
- Try to observe the color and transparency of the ice ball
- Now sprinkle a small amount of salt on the top the ice ball and observe the effect of sprinkling salt over the ice balloon
- Put a few drops of food coloring on the ice balloon and notice the melting flow pattern.
- Now put the ice balloon in the plastic tub containing some amount of water and observe how the ice balloon floats over water.
Science Behind This Experiment (What’s Going On?)
After peeling off the balloon from the ice balloon, you will notice that the ball has clear ice at the surface while opaque in the center of the balloon. This is because when we kept the balloon filled with water inside the freezer, it starts to freeze from outside to the center of the balloon. As it freezes it creates pure clear transparent crystals at the surface but the impurities such as air and minerals get collected and create a chain bubbles at the center of the ice balloon. These bubbles scatter light of all wavelengths and therefore, the center of the balloon becomes white and opaque.
When we sprinkle salt over the ice balloon surface, the ice starts to melt quickly. This is because as the salt dissolves with the film of the liquid water present on the surface of ice ball, salt lowers the freezing point of water below the ice’s temperature. The ice in contact with this film of salty water starts to melt and more salty water is created which causes more ice to melt. Hence salt acts as a catalyst which increases the rate of melting by lowering the freezing point of the water.
And when we add food coloring, the melting of ice becomes clearly visible and we can notice the flow pattern of the colored water which looks similar to flowing river water.
Now when we put the ice balloon in the plastic tub filled with water, we notice that the ice ball gets partially immersed into the water. The ice floats on water because liquid water has 9% more density as compared to ice. Now you must be thinking how is ice less dense than liquid? In general, when liquids are converted into solids, the space between the molecules gets reduced, and the density increases but it is not true in case of ice. Ice has cage-like structures that create a large number of empty spaces between the molecules. Hence, the volume of the ice increases and makes it less dense than water.
From the above experiment, we can conclude that
- The impurities such as air and minerals present in the water are responsible for the opaque and white color at the center of ice balloon
- Salt increases the rate of phase change from solid to a liquid by lowering the freezing point of water
- Ice floats on water due to its lesser density.