Solids, liquids and gases … oh, my! You’re probably familiar with these natural states of matter (plasma is the lesser known state.) Matter can change from one state to another. For example, when the temperature of water is lowered to 32 degrees Fahrenheit, it changes from a liquid to a solid. This is called “freezing.” Today, your friends from Museum of Discovery are going to explore a phase change that occurs when a solid turns into a gas using a fun and hands-on bubble activity!
When Blueberry called on the Museum of Discovery to explain what makes balloons float, Educator Corrie turned to helium.
Helium is an element (number 2 on the Periodic Table) that is a gas in its natural state which moves freely, like air, and cannot be seen. Because helium is lighter than air, when balloons are filled with it, they float. Corrie also did a demonstration with liquid nitrogen, which is, as stated in its name, the liquid form of nitrogen. Like helium, nitrogen in its natural state, is a gas. Another gas you are probably familiar with is carbon dioxide. Each molecule of carbon dioxide consists of one atom of carbon and two atoms of oxygen (CO2.)
When carbon dioxide’s temperature is lowered to -109 degrees Fahrenheit, it freezes and becomes a solid. Its solid state is dry ice. When the temperature of ice (frozen water) is raised, its phase changes from a solid to a liquid. This phase change is called “melting.” So, when the temperature of dry ice (frozen carbon dioxide) is raised, it must melt too, right? Not so fast! When dry ice is introduced to a warmer temperature, instead of turning into a liquid, it immediately changes into a gas. This phase change is called “sublimation.”
When you hold a chunk of dry ice using tongs in room temperature, you will notice that is looks like its smoking or fogging. That’s because as the carbon dioxide escapes, it is much colder than the surrounding air. The sudden drop in temperature causes water vapor in the air to condense into tiny droplets, forming fog.
When you place dry ice in warm water, it sublimates even faster. As the gas escapes, it rapidly expands within the water leading it to bubble. When the bubbles escape at the surface of the water, the warmer moist air condenses into lots of fog.
Now that you understand the process of sublimation, let’s have some fun with it, shall we?
Download a printable of the instructions here.
Here is what you will need:
You will soon see bubbles coming out of the straw. This happens because as the dry ice sublimates into carbon dioxide gas, it expands and fills the soapy water.
Make Large Bubbles:
If you are using a section of hosing or tubing, stick the small end of a funnel in the end of the hosing. As the gassy bubbles escape the funnel, they will grow larger around the exit of the funnel.