Dry ice is the solid form of carbon dioxide (CO2), which is a gas at room temperature. It’s used for making fog, in fire extinguishers, and to keep materials cold. Here’s a collection of interesting and cool dry ice facts.
Dry Ice Facts
- Dry ice looks a bit like regular ice. While it can be clear, it’s usually white because water vapor freezes into frost on its surface.
- Dry ice is very cold. It’s −78.5 °C or −109.2 °F, which is cold enough to cause frostbite.
- It’s called “dry” ice because it sublimates into vapor rather than melting into liquid. However, the liquid form of carbon dioxide does exist at higher pressure. Solid carbon dioxide melts into a liquid at pressure over 5 atmospheres, which you can achieve using a pressure syringe.
- Dry ice is more dense than water, so it sinks. Dry ice density increases as temperature decreases, ranging from 1.55 to 1.7 g/cm3.
- Due to sublimation, dry ice forms fog in air. This is actual water fog and not carbon dioxide vapor. Fog forms as the cold gas condenses water vapor in the air.
- Because of increased surface area, dry ice bubbles and forms fog vigorously in water. The carbon dioxide vapor is colder than air and sinks to the ground. Eventually, the gas mixes with air. Initially, the concentration of dry ice near the ground is higher. This can pose a suffocation risk in enclosed spaces.
- If you dropped dry ice in the ocean, it would form liquid carbon dioxide at a depth of about 50 meters (if it didn’t allow undergo sublimation before it reached that point). This is the depth when the water reaches 5 atmospheres of pressure.
- Dry ice causes a sour taste in dry ice ice cream or when it’s dropped in water or used to freeze fruit. The carbon dioxide reacts with water to form dilute carbonic acid. It also carbonates ice cream, water, or fruit with fizzy carbon dioxide bubbles.
- Sealing dry ice in a container is unsafe! Pressure build-up from sublimation can cause the container to burst. It’s best to store dry ice in a paper bag. You can place the bag in a foam cooler that has a lid that can pop open under pressure. You can put a bag of dry ice in a home freezer to slow the rate of sublimation. But, if there’s enough dry ice and the pressure gets high enough, it will open the freezer door. Dry ice sublimates at the rate of about five to ten pounds per day in a foam ice chest.
- The molecular weight of dry ice is 44.01 g/mole. It’s a nonpolar substance, with low thermal and electrical conductivity.
Dry Ice History
French inventor Adrien-Jean-Pierre Thilorier observed dry ice in 1835. Thilorier noticed opening a container of liquid carbon dioxide left a solid ice that evaporated without melting. Thomas B. Slate applied for a US patent in 1924 for a method of making solid carbon dioxide. DryIce Corporation of America trademarked the substance as “dry ice”. Initially, dry ice found use in refrigeration. Since that time, its uses have expanded to include food preservation, sample storage, flash-freezing, fire extinguishing, wart removal, beverage carbonation, insect baiting, rodent extermination, plumbing repair, and adhesive removal.
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